Before we start adding boost, it is important to point out that your transmission will affect the power output of your Mustang (measured at the wheels). An automatic will register roughly 30 hp less than a manual transmission.
Here is a statement Camaro owners already know, the 2015-16 Mustang is a force to the reckoned with. Despite the apparent lack of displacement (compared to the competition), the “little” 5.0L makes up for its size deficiency with terabits of technology, including DOHC cylinder heads, four valves per cylinder and variable cam timing. This technological combination allows the 5.0L motor to offer the torque curve of a 6.0L, to say nothing of impressive rpm potential. As good as the stock Coyote Mustang is, who among us doesn’t want even more performance?
Luckily enthusiasts need look no further than Kenne Bell to satisfy all their power needs, in one simply bolt on no less. The great thing about the Kenne Bell twin-screw supercharger kit is the amazing flexibility. As if the ability of the standard kit to add over 200 hp to your Coyote isn’t enough, additional boost can more than double those gains. Still not enough? The standard 2.8L is capable of supporting over 1,000 hp, but Kenne Bell offers even larger superchargers capable of exceeding 2,000 hp!
Before getting to the supercharger testing, it is important to understand why some 5.0L Coyote Mustangs register different power readings than others. Three critical factors that ultimately affect the measured wheel power output of the Coyote Mustang (actually all vehicles) include transmission, rear end type, and gearing. Extensive dyno testing has revealed that (despite the same motor output), a Mustang equipped with an automatic transmission will register a lower wheel power output than a manual transmission. There is more power loss (roughly 30 hp) through the automatic than the manual. Likewise for the new independent rear suspension, as the IRS will lose nearly 15 hp compared to a solid-axle Coyote. The final variable is the internal gearing in the rear end. Though it might improve acceleration, a higher numerical gear (3.73) will show less wheel hp than a lower numerical gear set (3.55, 3.27, 3.08 etc…). It is important to understand these variables as the change in power offered by these components will carry over to the supercharged outputs, and can make it difficult to compare early and late Coyote power outputs.
We touched on the different displacement superchargers offered by Kenne Bell, but the effectiveness of the twin-screw supercharger is a function of more than just sizing. The Kenne Bell supercharger is chock full of technology, including things like billet casing, an industry leading 6×4 rotor pack and Liquid Cooling. The strength of the external case is critical as improved case strength allows for tighter critical tolerances. These tolerances allow improved flow rates and boost potential through increased rotor speed. The case strength is then combined with the 4×6 rotor pack to further improve power while reducing inlet air temps.
Additional efficiency for the system comes from Liquid Cooling. Not to be confused with the air-to-water intercooler supplied with the kit, the Liquid Cooling system was designed to equalize the sizable temperature differential between the cold (inlet) and hot (discharge) sides of the supercharger. This temperature differential causes changes in tolerances on the hot and cold ends of the supercharger to eliminate high-rpm rotor scuffing common with other positive displacement superchargers. Kenne Bell designed the Liquid Cooling to minimize this temperature differential and to improve longevity of their superchargers.
One final word here before getting to the test results. A supercharger is only as good as the inlet system feeding it. Restrict the inlet system and you literally choke off the power and boost capability of even the most efficient supercharger. Obviously Kenne Bell recognized this long ago, as they have gone to great lengths to super size every component of their induction system. Included in the Kenne Bell inlet arsenal are the manifold, throttle body, MAF, and air intake. Starting with the restrictive factory air box, Kenne Bell designed a massive 4.5-inch, cold-air inlet, and MAF system (flowing 2,000 cfm). Naturally resizing (and repositioning) the MAF necessitated recalibration of the ECU, but the supplied supercharger program included the necessary changes. Finishing up the high-flow induction system, the Kenne Bell Mammoth intake was designed to accept the 168mm oval throttle body capable of flowing 2,150 cfm! Racers needing even more flow for a larger supercharger can always step up to the dual 106mm BIGUN throttle body assembly.
Technology and potential are all well and good, but how do they translate to real-world power numbers? To find out, we applied a Kenne Bell supercharger kit to a 2015 Mustang GT. Run on the Dynojet chassis dyno, the 2015 5.0L (manual trans) GT Mustang produced 381 hp and 378 lb-ft of torque at the wheels. After installation of the 50-state kit, featuring the 2.8L, twin-screw supercharger (at 10 psi), the peak numbers jumped to 620 hp and 507 lb-ft of torque (a 50-state kit is pending). Kenne Bell twin For The Win! Need more? Kenne Bell then added 130-pound Injector Dynamic injectors and 20V Boost-A-Pump (using the stock pumps) and cranked up the boost to 21 psi. The result was an impressive 843 hp. Remember, this was with standard 2.8L supercharger and no internal changes to the stock 5.0L Coyote motor. One of Kenne Bell’s customers managed nearly 950 wheel hp (on a Mustang Dyno) running E85 fuel on the stock motor. This combination was used to exceed 200 mph in the standing mile.
The stock 5.0L Coyote was no slouch, pumping out 385 hp and 378 lb-ft in normally aspirated trim. After installation of the Kenne Bell supercharger kit, this jumped to 620 hp and 507 lb-ft of torque at 11 psi (93 octane). Kenne Bell has exceeded 840 hp on the stock motor using race fuel, a Boost-a-Pump and larger injectors.
Are you going to run a hydraulic flat tappet camshaft and not sure how to break it in? Edelbrock takes a look at the proper break in procedures to ensure long life out of your performance cam.
What adds more power to your LS, bolt-ons or the bottle?
Words & Photos By Richard Holdener
We will start by ending the suspense, as we had no intention of choosing between bolt-ons and the bottle and instead applied both to our 5.3L LM7. In fact, we went one better and stepped up the displacement as well, but technically speaking, the stroker components fit nicely in the bolt-on category anyway.
We all know that the right heads, cam, and intake will yield substantial performance dividends on almost any motor, but certainly on an LS application. When you combine the airflow improvements with increased displacement, things get even better. Now if you top all that off with some Zex happy juice, you wind up with one seriously fortified 5.3L.
To get thing started, we ran our stock 5.3L LM7 on the engine dyno with headers, an open throttle body, and Meziere electric water pump. The otherwise stock 5.3L produced 353 hp at 5,200 rpm and 384 lb-ft of torque at 4,300 rpm.
While the discussion here has been primarily about power production, the combination also improved both idle quality and drivability. Let’s not forget the abundance of torque offered by the extra cubic inches, as the low-speed grunt is even more useful than peak power gains. Think about how many times you rev the motor out to redline versus the times you just stab the throttle and motor through the mid range. Yep, strokers are fun in the sun and a nitrous-injected version can be even more so.
How is a stroker able to improve idle quality and drivability, you ask? The key is the effect displacement has on relative cam timing. If we modified a typical 5.3L with ported heads, wilder cam timing and a decent intake manifold (like our FAST LSXRT), the result would not only be a motor looking to make peak power up near 7,000 rpm, but one with reduced idle quality and drivability. Such is the trade-off when making big power with little motors.
By contrast, if we increase the displacement of the 324c.i. 5.3L to a solid 383c.i, the extra displacement actually tames the cam timing. Using the same components as the high-rpm 5.3L, the larger 383 will make peak power much lower and will have much-improved idle quality and throttle response. Stab the throttle, and instead of waiting for the little 5.3L to come on the cam, you are rewarded with an abundance of torque. Remember, the stroker adds power everywhere, from right off idle all the way to redline.
A little math tells us that if we built a 475-hp 5.3L, using heads, cam, and intake, it would equate to 1.466 hp per cubic inch. If we applied that same efficiency to the larger 383, we would get 561 hp. Bigger really can be better!
To achieve the proper combination of displacement and efficiency, we started by disassembling and machining the 5.3L to accept stroker components from Speedmaster and Mahle. The 4.0-inch stroker crank and forged 6.125-inch rods came from Speedmaster, while the forged, flat-top slugs were supplied by Mahle.
Though full roller rockers are available for LS applications, we elected to stick with the factory rockers on the 383.
The 4.0-inch crank combined with the 3.905-inch bore produced a finished displacement of 383 inches. This stroker was fortified with a COMP 281LR HR13 cam that provided a .617/.624 lift split, a 231/239-degree duration split, and 113-degree lsa. The cam was combined with new drop-in replacement lifters and hardened pushrods from COMP Cams.
The short block was topped with a set of CNC-ported LS heads from Speedmaster. The CNC heads flowed over 300 cfm, or more than enough to support our power needs. The heads were treated to a dual valve-spring package that provided adequate pressure and coil-bind clearance for our cam profile. Feeding the heads was a FAST LSXRT intake and matching 102-mm, Big-Mouth throttle body. Controlling the 75-pound FAST injectors was a FAST XFI/XIM management system.
Topping the ported heads on the 383 stroker was a FAST LSXRT intake and matching 102mm, Big-Mouth throttle body.
Run in anger after the build and break in, the 383 produced 544 hp at 5,900 rpm and 514 lb-ft of torque at 4,800 rpm. That represented a sizable jump over the 353 hp and 384 lb-ft of torque produced by the stock 5.3L. Now it was time for some Zex!
The Zex Perimeter Plate Blackout system was designed specifically for LS applications. The trick system featured a unique intermediate plate designed to sandwich between the throttle body and intake manifold. The design team at Zex even went so far as to make the plate a direct fit for all 90mm (factory) and larger aftermarket manifolds. This obviously included the FAST LSXR and LSXRT intakes.
Run on the dyno with long-tube headers, the modified 383 stroker produced 544 hp at 5,900 rpm and 514 lb-ft of torque at 4,800 rpm. So far, the bolt-ons were working well.
Credit a machined (o-ringed) insert for the adjustability to step down the 102mm opening to fit the smaller 90mm throttle bodies and intakes. Online information indicated that the Zex Perimeter Plate system offers a number of interesting and potentially powerful design features, including Perimeter Injection, Cryo-Sync, and Airflow Enhancement technology.
The boost-in-a-bottle portion of the equation was supplied by Zex in the form of their Perimeter Plate. The trick plate featured an insert (with o-ring) to size the opening for the desired throttle body. The plate was even labeled for proper orientation.
The Perimeter Injection employed 12 separate injection points that combined both nitrous and fuel to optimize atomization and distribution in the manifold. The introduction of nitrous at -127 degrees effectively turned the plate into a Cryo-Sync (or heat isolator). The high-pressure flow nitrous through the spacer plate also worked to create a low-pressure zone to further enhance airflow into the motor.
Both the fuel and nitrous solenoids were bolted in place to the FAST intake manifold. The kit featured black braided lines to feed nitrous and fuel from the solenoids to the jetting on the Perimeter plate.
For our test, we set up the Perimeter plate system with jetting to supply an additional 150 hp. The Zex system is adjustable from 100 to 250 hp, so the available jetting had no problem supporting our power needs. We heeded the advice supplied with the nitrous kit and retarded the timing by six degrees for the 150-hp shot. To hedge our bets, we splashed the 91-octane pump gas with some 100-octane Rockett Brand race fuel.
Run with the Zex Perimeter Plate equipped with 150-hp jetting, the nitrous-injected 383 produced 695 hp and 696 lb-ft of torque.
The 383 relied on a manual throttle body for this test, but it is important to point out that the Zex Perimeter Plate system was also designed to run on drive-by-wire applications. All we can say is we love testing nitrous, as activation of the kit brought with it a jump in power to 695 hp at 5,900 rpm and 696 lb-ft of torque at 5,000 rpm.
Upon activation, the Zex Perimeter Plate kit offered consistent gains through the tested rev range. The modified stroker offered plenty of power over the stock 5.3L, but what really made it sing was the Zex nitrous kit. So which is better, bolt-ons or the bottle – the answer is obviously both!
The right heads and cam can literally transform your BBC!
Big-block Chevy owners share a common goal with all enthusiasts. That goal is a simple one – make more power? As luck would have it, the answer to that question is quite simple.
There are endless ways to improve the power output of almost any internal combustion engine, including the 540-stroker used for this dyno session. When you go looking to improve the power output, one of the first things that comes to mind is forced induction. True enough, adding a turbo or supercharger to even your otherwise stock motor will result in a significant power gain.
We know, we did this to the Power Adder crate motor from BluePrint Engines with great success. The same can be said for a small (or even large) dose of nitrous oxide. Adding juice to your motor can literally transform it from mundane to maniacal, depending on the amount supplied.
The final avenue is likely the most popular, often labeled the bolt-on, or all-motor route. This involves replacing, or otherwise improving, the existing engine components to improve the breathing potential or efficiency. Things like ported heads, cams, and free-flowing induction systems fall into this category.
While the other methods certainly have their merits, we chose the all-motor route for improving the power output of this 540c.i. BBC crate motor. We previously ran the BPE BBC Power-Adder crate motor with nitrous, a pair of superchargers (actually three) and turbos, but this time we opted to improve the normally aspirated power. Naturally, you can later combine these all-motor improvements with forced induction and/or nitrous oxide for a more serious effort, but let’s take things one step at a time and add power by improving what we refer to as the “Big Three”.
We replaced the milder blower cam with a healthy, solid-roller cam that offered a .748/.714 lift split, a 276/284-degree duration split and 110-degree lsa.
In terms of a performance engine, the “Big Three” refers to the top end of the motor, namely the heads, cam, and intake manifold. The reason for the “Big Three” label is that these major components all but dictate not only the power output of the motor, but also the overall power curve.
Of course the short block must be up to snuff to accept the significant change in power. There are other components that can be employed to fine tune the power output, but the major players are still the heads, cam, and intake.
The test motor was already a healthy unit. Supplied as a crate long block, the BPE 540 was designed for use with power adders and built accordingly. Starting with their own HD, 4-bolt block, the BPE 540 was treated to forged internals, including a 4.25-inch stroker crank and, 4.50-bore, forged pistons swinging on forged, H-beam rods.
The short block also featured a dedicated blower cam, though it ran equally well with nitrous and a pair of turbos. The solid-roller profile offered .652 lift, a 255/262-degree duration split and 114-degree lsa. Naturally the big block also received solid-roller lifters, hardened pushrods, and a complete oiling system.
Topping the stout short block was a set of as-cast, aluminum rec-port heads. For dyno use, we added an Edelbrock 454-R intake, 950 XP Holley, and MSD billet distributor. Know that we made over 1,300 hp with the turbos using this basic combination, so it was no slouch as supplied by BPE. Run in normally aspirated trim, the low-compression 540 produced 648 hp at 6,000 rpm and 629 lb-ft of torque at 4,500 rpm.
The combination worked amazingly well under boost, but we couldn’t help but wonder if there was more power just waiting to be unleashed from the normally aspirated combination? With power on our mind, naturally we looked to replacing the Big Three.
Off came the BPE, as-cast aluminum heads to make way for the AFR head swap. The heads were installed with Fel Pro MLS head gaskets and ARP head bolts (both heads used the same head bolt combination).
Starting with the cylinder heads, the aluminum, as-cast, rec-port heads from BPE were replaced by a set of CNC-ported, AFR 377 Heads. Actually overkill for this application, these AFR heads were actually destined for a larger 565 build up using a World Product block, but since we had them available, we decided to test the big-three upgrade on this 540.
The AFR heads featured 377cc intake ports that flowed over 435 cfm, albeit at .900 lift. Hardly high-lift wonders, the 377 AFRs flowed 415 cfm at just .600 lift, meaning there was plenty of flow to feed the 540. Run on a wilder BBC combination, these AFR heads could support over 875 hp, but we would get nowhere near that number on this low-compression application. The AFR 377 heads also featured a 2.30/1.88 valve combo, a solid-roller spring package and CNC-profiled, 121cc combustion chambers.
To add a touch more lift, we installed a set of Crane, BBF 1.73-ratio aluminum roller rockers. AFR supplied a set of adjustable guide plates to help us individually line up each rocker.
To take advantage of the airflow offered by the AFR cylinder heads, the 540 needed wilder cam timing. Though a solid roller, the BPE blower cam was replaced by a much more aggressive unit from the COMP Cams catalog. The Super Gas grind (pt#11-734-9) featured a .748/.714 lift split (with 1.7 rockers), a 276/284-degree duration split and 110-degree lsa. This represented a significant step up in cam timing from the original blower cam.
The cam was combined with the solid-roller lifters supplied with the crate motor, but the new heads required different (hardened) pushrod lengths and replacing the double-roller timing chain. The blower cam was designed for use in a Gen VI block (the BPE featured a Gen VI cam-retaining plate). The new cam was designed for the earlier Mark IV BBC (with no cam retaining plate). The cure was to use a new Mark IV timing chain combined with a cam button to properly locate the cam. The final touch was a set of 1.73-ratio (BBF) aluminum roller rockers, bringing the final (pre-lash) lift figures to .761/.727.
The final modification to our 540-stroker was the induction system. Though the Edelbrock 454-R intake and 950 HP Holley were well-suited to the milder 540, we wanted to step things up on the new combo. To that end, we gathered together an Edelbrock Super Victor and Holley 1,050 Ultra Dominator. Any self-respecting big block should be sporting a Dominator, but if you decide on one, make sure to step up to the Ultra series (worth it on weight savings alone).
We retained the MSD billet distributor and plug wires, along with the dyno headers, but did cover the AFR 377 heads with the supplied cast-aluminum (AFR logo) valve covers. Our motto has always been if you got it flaunt it! Given the previous use with power adders, our big-block was well seasoned and ready for action.
BPE 540-Effect of AFR Head/COMP Cam Upgrade As you can see from the results, the AFR 377 heads and COMP (drag-race) roller cam offered some sizable power gains. The power output of the low-compression, power-adder 540 from BPE increased from 648 hp and 629 lb-ft of torque to 734 hp and 633 lb-ft of torque. As is evident, the free-flowing AFR heads and wilder cam timing pushed power production higher in the rev range, with the horsepower peak coming 800 rpm higher and the torque peak coming 1,000 rpm higher.
After dialing in the tune with one jet change, we were eventually rewarded with peak numbers of 734 hp at 6,800 rpm and 633 lb-ft of torque at 5,500 rpm. As expected, the wilder cam timing and free-flowing heads shifted the power higher in the rev range, but the losses below 4,000 rpm were more than offset by the gains up top. Now sporting an extra 86 hp, this stroker is just begging for more boost.
Let’s get this over with right now – if you will accept the concept of strength in numbers, the small-block Chevy is still the king. Sure, the LS family deserves all the hyperbole. But that doesn’t change the fact that there are more traditional small-block Chevys running around wild in the streets in hot street cars than all the others. It’s probably etched in a stone table somewhere. There are still rodders interested in budget-based small-block Chevy stories and this one deserves updating.
If you’re on a Mac ‘N Cheese budget but you’d still like a little torque under your right foot, you’ve probably heard about the power payoff of Vortec heads. For those who may be new to the game, the Vortec head was first introduced on the L31 350ci truck engines in 1996. Despite their journeyman use, these heads flow dramatically better than any other small-block Chevy production head, which makes them popular with just about anybody who wants to build a mild street small-block. Used Vortecs are still around or you can purchase these castings brand new from Chevrolet Performance. We found them on Summit Racing’s website for less than $330 apiece – complete and ready to run.
While these heads will bolt right on a small-block Chevy, there are several caveats that you should be aware of before you torque those head bolts down. First, these heads employ a unique 8-bolt intake bolt pattern that’s different compared to the standard small-block Chevy 12-bolt pattern, requiring a dedicated Vortec manifold. Next, the Vortec head employs a small, 64cc combustion chamber. This is great for stock short block 350 engines like the Chevrolet Performance 290 hp 350 crate engine that uses a dished piston with a 76cc combustion chamber head. That creates an 8.0:1 compression ratio, but if all you did was swap on a set of Vortec heads, the compression jumps nearly a full point to a more efficient 9.0:1. With a common, four-eyebrow flat top piston and a .041-inch thick head gasket on a 350ci engine, the Vortec head will bump the compression to around 9.5:1 depending upon the deck height.
There are other, smaller points that are important to know because they affect cam selection. If you intend to run a very mild cam with less than 0.440-inch lift, then simply bolt these Vortecs on and have a nice day. But today, even a stone stock 5.3L LM4 LS truck engine sports 0.466-inch lift, so building a street Vortec-headed small-block demands a cam with at least 0.475-inch of valve lift. But there’s the rub. The stock Vortec iron head will not tolerate more than 0.440-inch lift. We measured our stock iron heads right out of the box and the retainer-to-seal clearance was only 0.470-inch. Subtract the standard 0.050-inch clearance, this leaves only enough room for a 0.420-inch lift cam. That just won’t do. But don’t despair. Just get out your tools and make some modifications.
While some hot rodders would probably take their heads to their favorite machine shop and let their shop do the mods, we’re here to tell you that the mods these heads need are easy to do yourself with a custom milling tool, a ½-inch drill motor, and a clean spot on the work bench can accomplish.
The Vortec head features a very large boss at the base of the valve guide that measures 0.850-inch in diameter and is used to locate the 1.250-inch outside diameter (O.D.) valve spring. The head uses 0.560-inch I.D. seals mounted directly on the top of the guide. This guide boss is also very tall. This height restricts the room between the top of the seal and the bottom of the valve spring retainer at max valve lift. There are two simple approaches to modifying the head to accept a performance valve spring that will create the room necessary to allow greater valve lift.
The easiest solution is also the most expensive. COMP Cams builds a beehive style valve spring that drops right in place of the stock spring along with new retainers and valve locks. The beehive spring uses a much smaller retainer that produces additional clearance to the stock seals. With the beehive, this instantly improves the retainer-to-seal clearance to 0.500-inch, which means you could run a 0.470-inch lift cam with a tight 0.030-inch clearance. The beehive springs we chose (PN 26915) drop right in place and no machine work is necessary and even the original seals can be reused. The detraction to this approach is cost – the beehive springs are more expensive than a conventional spring and with retainers and locks, the price comes to roughly $260.
The second solution is less expensive but requires more effort and to purchase a machine tool to modify the valve guide boss to add clearance. COMP sells a slick little tool that will machine the guide down to a 0.530-inch O.D. seal size while also lowering the boss height. The boss height of our heads measured 0.730-inch from the spring seat. It is this height that minimizes the seal-to-retainer clearance. With the tool set up in our ½-inch drill motor, it took a few minutes to machine all 16 guide bosses, being careful to lower the guide height only enough to create 0.550-inch retainer-to-seal clearance. We discovered that our 981 spring would just clear the wider base after the top of the guide was machined because the damper was the only portion of the spring that hit the guide boss. If spring shims are required to set the installed height, you will need shims with an inside diameter of 0.875-inch to clear the guide boss. COMP also offers another machine tool that will narrow the guide boss and also increase the spring seat diameter, but we elected not to use that tool. With our machining completed, we cleaned all the cast iron shavings, reassembled the heads, and the job was complete.
For those who would rather buy a set of heads already converted, Scoggin-Dickey Parts Center in Lubbock, Texas offers several options that are a good deal. We did the math and if you have a set of used Vortec heads, the conversion to the COMP 981 springs will cost $236. But if you are considering buying a brand new set of Vortec heads, Scoggin-Dickey offers an already modified and assembled Vortec head. The guides are machined to increase retainer-to-seal clearance to accept 0.0525-inch valve lift and the heads include a set of Z28 springs and retainers. You might as well buy the Scoggin-Dickey heads because their price is almost exactly the same. We couldn’t find the specs on the Z28 springs but we’ll assume the springs are roughly equivalent to the COMP 981 springs.
Just to give you yet another option, Chevrolet Performance also makes what is called a Vortec Bow Tie head in two different port sizes. Both the small- and large-port heads feature 2.00/1.55-inch valves, 66cc combustion chambers, are drilled and tapped for screw-in 3/8-inch rocker studs (no guideplates), the intake port is drilled for either the typical Vortec patter or for a tall port conventional small-block intake manifold bolt pattern. Finally, these heads offer both a perimeter small-block valve cover bolt pattern and the center-bolt configuration. The small intake-port version measures 185cc (larger than the stock Vortec) while the large-port measures a much larger 225cc. These heads are only slightly more expensive than the modified stock Vortec head and offer some significant improvements.
So the Vortec cylinder head landscape has changed a little over the years with plenty of options for those willing to do a little work. As the great Mark Twain once wrote in Huckleberry Finn, “You pays your money, and you takes your choice.”
Simple Driveshaft Speed Calculations that Could Prevent a Disaster
Words And Photos: Jeff Smith
We had this crazy notion to race a ’65 Chevelle at the Pony Express. This was an open road race in 1998, and we wanted to enter our car in the 150 mph class where we had to average 150 mph for 90 miles driving on a 2-line primary highway in the Nevada desert. We had performed our top speed versus engine rpm calculations and the numbers looked promising. The plan was to use a Richmond 6-speed manual transmission with a 0.62 overdrive and a 3.55 rear gear. Our top speed simulation program predicted we had enough power to overcome the Chevelle’s hideously poor aerodynamics to run as fast as 170 mph. For the record, the Chevelle was recorded at 168+mph at the Pony Express in 1998.
That spinning driveshaft might not seem like a source of trouble, but when a 20-pound shaft is spinning at 5,000 rpm, it contains a tremendous amount of stored energy. It’s wise to make sure that shaft is happy and safely avoiding its critical speed when spinning at max velocity.
During our planning session, providence stepped in and a friend with high-speed racing experience suggested we speak to a driveshaft specialist about our intentions. Our benefactor mentioned something about driveshaft critical speed — a term with which we were completely unfamiliar. What we discovered was our 38 percent overdrive was going to spin our driveshaft so fast it would easily exceed its critical speed — a very dangerous situation when running at 140-plus mph.
Driveshaft critical speed is the equivalent rpm that matches the shaft’s first order natural frequency. When critical speed is achieved, the driveshaft will begin to whip or bend in the middle. This is crazy dangerous because when this bending occurs, it not only affects balance but also effectively shortens its length and the slip yoke can either be pulled out of the transmission or will fail due to insufficient contact with the transmission output splines.
So, imagine the carnage that occurs when a driveshaft (spinning at 5,500 rpm) fails while the car is running at perhaps 150 mph. All that kinetic energy begins beating on the floor, breaking through the thin sheet metal into the interior, all while the driver is trapped in his seat. It’s not a pretty thing to consider the consequences.
The best way to prevent this disaster is to take a few moments to calculate your driveshaft critical speed if you are considering any top speed runs. In the past 10 years, high-speed measured mile (and now two-mile) runs at airports have become popular. Even long-wheelbase muscle cars are capable of 150 mph passes, so this story isn’t just about a few 200-mph cars.
Securing a more favorable critical speed can be achieved by changing any of several driveshaft variables. We’ve listed these variables in the accompanying chart, but in review, they include the length of the driveshaft, the driveshaft rpm, the tubing diameter, the material, and the true driveline operating angle. While each of these components affect critical speed, it’s the combination of all five that create the final rpm number.
Let’s start with length. As driveshaft length increase, critical speed is lowered, regardless of the shaft’s material. Another way to say that is crucial speed is inversely proportional to driveshaft length. This means that a shorter driveshaft is inherently stronger than a longer unit. Tubing diameter is also a fairly simple concept, as a larger tube will be stronger with an inherently higher critical speed. So, if a change in length is not possible, increasing the tubing diameter will help.
Until a few years ago, driveshaft material selection was limited to steel — either mild steel or 4130 drawn-over-mandrel (DOM) tubing — or aluminum. While these are still viable, we now have a third option with carbon fiber. The advantage to carbon fiber is its incredible strength relative to its weight.
As you can see from the chart supplied by Mark Williams Enterprises, carbon fiber delivers an amazing critical speed advantage for a given length and diameter. A 3.5-inch diameter carbon fiber driveshaft has a 53 percent higher critical speed than a 3.0-inch steel driveshaft. Just as important, several companies now make carbon fiber driveshafts, which means competition should help reduce the price.
This is what happens when a driveshaft is not happy. Now, imagine this happening underneath the car at 140 mph and it comes up through the floor, hunting for the driver. Not good.
Next is the operating rpm. This may sound simple, but it’s easy to overlook the effect of an overdrive transmission on driveshaft rpm. Let’s take a simple situation where the transmission offers a 0.70 overdrive ratio. Most enthusiasts view the overdrive from the perspective it lowers engine speed, which it does. As an example, as soon as the transmission shifts into overdrive, the engine speed is reduced by 30 percent. But this also means the driveshaft rpm is now 30 percent faster than it was in the 1:1 gear. Stated another way, at 100 mph with a 1:1 high gear, a 3.55:1 rear gear, and 26-inch-tall tires, the engine would spin 6,422 rpm. But add an overdrive ratio of 0.70:1 and the engine speed plummets to 4,495. The driveshaft, however, is still spinning at 6,422 rpm.
The final point is the driveline’s operating angle. This is not just the simplistic angle of the driveshaft. The entire operating angle is a far more complex consideration that considers the operating angles of the u-joints in both the side view and also the top view. This is called the compound operating angle — something that is almost totally ignored, yet can be a significant consideration.
We’ve included a condensed version of a chart that can be found on Mark Williams’ website that lists the critical speed for driveshafts of multiple length, diameter, and material composition. Remember these speeds assume an ideal operating situation with minimum u-joint operating angles. If your operating angles are less than ideal, expect the critical speed to be far lower than what is listed in the Mark Williams chart.
The best way to put all this into perspective is to use a specific example and show how all these factors can be integrated to determine the best driveshaft selection.
Let’s start with some simple calculations to illustrate how the numbers will play out to choose the right driveshaft. To begin, we must be able to calculate driveshaft rpm based on vehicle speed, gear ratio, and drive tire diameter. Here’s the basic formula using a 3.08:1 rear gear and a 26-inch-tall rear tire to calculate engine rpm at 140 mph:
Engine RPM = (MPH x Gear Ratio x 336) / Tire Diameter
Engine RPM = (140 x 3.08 x 336) / 26
Engine RPM = 144,883 / 26
Engine RPM = 5,572
This puts our engine right at peak horsepower at the top speed we desire. This also assumes a 1:1 high gear ratio like with a four-speed. If this was used in our ’65 Chevelle, it also requires a 60-inch long driveshaft. Our chart only goes to 58 inches, so let’s assume we can make a 58-inch driveshaft work. The critical speed for a 3.0-inch steel driveshaft is 5,062 rpm — which clearly won’t work.
The reason this won’t work is that at high speeds, the car is very slowly accelerating as it nears top speed. This means the engine will reside at a little over 5,000 rpm for a long time as it accelerates to top speed. We can’t take the risk of slowly transitioning through the driveshaft’s resonant speed. We will need to find a different driveshaft at the same length that offers at least a 15- to 20-percent safety factor over the critical speed.
This Tremec illustration used in their app indicates the parallel angles necessary to ensure proper u-joint operating angles. Note the engine and transmission angle is tail down with the pinion angle nose up. If the pinion was nose-down, this would produce a conflicting operating angles.
So, what can we do? A 20-percent safety factor would be: 5,572 x 1.20 = 6,686 rpm or higher. On the chart, we can see there are two driveshafts that will give us the rpm we need. One is a 4.0-inch diameter bonded aluminum driveshaft with a critical speed of 6,733. The problem with a 4.0-inch driveshaft in an early Chevelle is that we would have to cut and raise the stock tunnel to clear that large of a driveshaft. The other shaft that would work is a 3.75-inch carbon fiber unit with a critical speed of 7,756 rpm — clearly with more than enough safety factor.
Another solution would be to change the rear gear to a 2.56:1 ratio combined with a 1:1 high gear transmission. This taller gear would put engine and driveshaft speed at 4,631 rpm, which achieves more than a 25-percent safety factor for a 3.5-inch performance steel driveshaft’s critical speed of 5,963 rpm. Note that a 3.0-inch steel driveshaft would still be too close with its 5,062 rpm that does not achieve a 10-percent safety factor.
The only problem with a 2.56:1 rear gear is that acceleration up through the gears will be soft. A popular option is to use a deeper gear for acceleration and then pop the trans into overdrive to reduce total engine rpm. We could use an overdrive unit to slow the engine speed, but remember this increases the driveshaft speed — and can easily push the driveshaft into or past its critical speed. Let’s try a combination to see what that achieves.
The variables are a 3.55:1 rear gear, a 0.62:1 overdrive (Richmond six-speed), a 26-inch-tall tire, and a new top speed goal of 170 mph. That may sound crazy, but it’s close to our original combination with our Chevelle in 1998. For a final drive ratio, it’s necessary to multiply the 6th gear overdrive ratio of 0.62 x 3.55 (rear gear ratio) = 2.20:1 for the final drive ratio.
Engine RPM = (MPH x Gear Ratio x 336) / Tire Diameter
Engine RPM = 170 x 2.20 x 336) / 26
Engine RPM = 4,833
Driveshaft RPM = Engine RPM x Inverse of Overdrive (inverse of 0.62 = 1.38)
Driveshaft RPM = 4,833 x 1.38 = 6,670
As you can see, this doesn’t help because of the excessive driveshaft speed. There were no (affordable) carbon fiber driveshafts available for our Chevelle back in 1998, so we had to revert back to the previous 2.56:1 rear gear combination without overdrive.
Now that we have a handle on critical speed, let’s look at something called half critical speed. First order vibrations occur at shaft speed, but because the u-joints move twice per revolution, a driveshaft spinning at half of the critical speed can create a vibration. This may seem unimportant, but with an overdrive transmission spinning the driveshaft 30 percent faster than engine speed, it is entirely possible. What we want to avoid are those annoying vibrations at normal highway cruise speeds.
Let’s take a look at a common combination of a street gear ratio, a long driveshaft, and an overdrive automatic transmission. The combination in our 383c.i. ’64 El Camino is a 4L60E automatic with a 0.70 overdrive, a lockup converter, a 3.36:1 rear gear ratio, and a cruise speed of 70 mph.
Half Critical Speed MPH Calculation
3.36:1, 4L60E (0.70:1), 26-inch-tall tire, 70 mph
Engine RPM = (MPH x Gear Ratio x 336) / Tire Diameter
Engine RPM = (70 x 2.35 x 336) / 26
Engine RPM = 2,126 at 70 mph
Driveshaft RPM = 2,764 at 70 mph (30 percent faster)
With a driveshaft length of 56 inches, the critical speed of a 3.5-inch diameter, mild steel driveshaft is 6,403 rpm. So half critical speed 6,403 / 2 = 3,201 Driveshaft RPM = 105.4 MPH. To double-check our work, we plug the speed back into this formula:
Engine RPM = (MPH x Gear Ratio x 336) / Tire Diameter
Engine RPM = (105.4 x 2.35 x 336) / 26
Engine RPM = 3,201
A big part of minimizing issues with driveline vibration has to do with ensuring the driveline operating angles are within spec. Tremec offers a free app for smart phones that will measure the operating angles and do the calculations for you. This is our friend Scott Gillman measuring the shaft angle on his Advanced Composites carbon fiber driveshaft — we’re jealous.
So it appears our cruise speed will not be affected by half critical speed issues until we try running the car up to 105 mph. This may create a vibration, but the chances of that happening are slim as long as our operating angles are optimized.
The last words on critical speed should be left to ensuring that the operating angles of the driveline are as accurate as possible. We’ve written a tech story on using the Tremec Driveline Angle Finder App on a smart phone. This app uses the angle function on a smart phone to quickly determine the driveline’s true operating angles. This story can be found on HERE on PowerPerformanceNews.com.
To simplify the driveline operating angle as much as possible, the key with any one-piece driveshaft using a pair of u-joints is to establish the proper operating angles under load. If the engine and transmission are in the typical tail-down orientation, it’s important the rear axle pinion angle be pointed upward at roughly the same angle. So, if the engine was pointed tail down 2 degrees, then the pinion flange on the rear end should be pointed upward at roughly the same angle. An angle difference of up 1 to 3 degrees is acceptable.
This places the two u-joints at minor operating angles so they turn slightly as the driveshaft goes through each revolution. What should be avoided is a conflicting angle where the engine/trans is pointed down and the pinion angle is also pointed down. This creates a conflicting angle that will cause the u-joints to rotate in an ellipse, as opposed to a true circle. Re-orient both u-joint operating angles into a parallel relationship and the u-joints will operate in a true circle and the vibration disappear.
In the early days of racing when race cars struggled to break 100 mph, driveshaft issues were minimal because of the low speeds. But now that street cars have the potential to approach or exceed 200 mph, the physics of a spinning driveshaft become of paramount importance. So, do a few measurements, punch the buttons on your calculator for a few minutes, and see where your combination pencils out. You might be surprised.
Driveshaft Critical Speed Variables
Tube Diameter – larger increases critical speed Material – Increasing order of critical speed: mild steel, aluminum, carbon fiber Length – a shorter driveshaft offers a higher critical speed Angles of Operation – conflicting angles can cause a vibration Driveshaft RPM – Overdrive increases driveshaft speed compared to engine rpm.
Driveshaft – Material
46”
48”
50”
52”
54”
56”
58”
4” Bonded 6061 Aluminum
10,817
9,913
9,118
8,415
7,791
7,233
6,733
3.5” 6061 Aluminum
9,345
8,567
7,883
7,278
6,739
6,259
5,828
3.75” Carbon Fiber
12,453
11,414
10,500
9,692
8,973
8,331
7,756
3.5” Mild Steel 4130
9,557
8,762
8,063
7,444
6,894
6,403
5,963
3.0” Mild Steel ML-600
8,129
7,450
6,854
6,326
5,856
5,856
5,062
This chart lists the critical speed for five different driveshaft materials and diameters based on length. As length increases, critical speed drops. For example, there is a 37-percent reduction in critical speed for a 3.5-inch mild steel shaft when changing length from 46 to 58 inches. Chart courtesy of Mark Williams Enterprises.
What kind of gains will our Sale Director’s Roush Mustang see over a simple header swap?
Photos by Jonathan Ertz/Words by Elizabeth Puckett
Ivan is our Sales Director over here at Xceleration Media, and his 2015 Mustang GT is turning some heads, and that’s not just because it’s a great looking pony car. With only a few mods, this Roush Mustang has dipped down into the high 9s, proving that forethought put into mods will get you pretty far.
The last time Ivan went to the track, his 2015 Ford Mustang with Roush Performance TVS went 9.88@140mph! It is tuned by Palm Beach Dyno, has a 72mm upper (11.7psi), runs on e85, had the stock catback exhaust, Sai Li return fuel system, id1000 injectors, BMR Suspension springs, Jms Chip wheels, and Mickey Thompson tires. Everything else was stock including engine, trans and rear end. The car (with driver) weighed in at 4025lb.
In the pursuit of a faster setup by spring, Ivan decided to throw a pair of silver ceramic coated BBK longtube headers, and high flow mid pipe on his Mustang.
BBK made these headers as the first direct fit, full length longtube headers for the 2015-17 Ford Mustang 5.0. These headers are designed for one thing, gains! Testing through BBK has proven significant horsepower and torque gains, and once you scroll to the end, you’ll see what Ivan’s Mustang picked up.
Unlike many of its older brothers, the sixth-generation Mustangs are champs when it comes to exhaust work.
Having access to a lift is a benefit over laying on your back while the car is on jack stands, but the headers themselves and the way Ford ran the exhaust is a better design than you’d see on the Mustang during the early 2000s and back.
The main trick to making this job super simple was jacking the engine up for better access. After supporting the engine with a screw jack, the starter was removed, engine mount brackets removed, and the engine could be raised to create more room to reach the header nuts. A few nuts had to come out from the top of the engine, so removing the air box was needed to get that extra access up top.
Mid pipes from BBK will replace the catted pipe behind the headers.
The new headers and mid pipe went back on as easily as the manifolds and cats came off. The stock cats were ditched and replaced with a catless mid pipe.
The sound profile was noticeably different right away, with a louder and more aggressive tone — the exhaust is still being run through stock mufflers.
The whole job was very straight forward, start to finish. Total install time was 5 hours, and there were no surprises along the way. Once it’s off the lift, it’s off to the Mustang dyno to see what kind of power you gain with only 5 hours worth of work.
Baseline dyno numbers were taken using an 85mm supercharger pulley, 93 octane pump gas, and only 7-8 psi of boost. This was the largest supercharger pulley they make for this blower. The only changes on the post-install dyno pull were the longtube headers and removal of cats/installation of catless mid pipe. The baseline pulls vs. post-header install pulls reveal a massive horsepower and torque gain. Ivan’s Mustang picked up peak numbers of 42hp and 41ft-lbs of torque, and even more through parts of the power/torque curves.
This was done in a temperature controlled facility, so the install was the only thing that made a difference. Ivan also noted an immediate difference in the pedal, which is equally as important since this is a daily driven car — it’s no track queen! We will update the track times when the weather permits the tracks to reopen in the spring.
It’s a warm summer night where sound can carry for miles. Off in the distance, you hear the strains of a performance engine quickly rowing through the gears. The 1-2 and 2-3 shifts are crisp and well-executed, and in your mind’s eye, you see the driver pulling back on the shift handle into fourth gear, anticipating another quick gear change. Instead, you hear the unloaded engine scream as the gears fail to mesh. Whiffed it!
It’s the classic missed shift. If you are a manual transmission fan, you’ve heard it and probably experienced it. Most enthusiasts of the art will quickly attribute the failure to driver error — a lack of hand-foot coordination. But, there might be another explanation. It could be the bellhousing is not doing its intended job. Let’s look at how this works.
Besides giving the transmission a solid location and perhaps providing protection from an exploded clutch, the bellhousing has only one important job. That’s to make sure the transmission input shaft is perfectly aligned with the centerline of the crankshaft. But, production tolerances being what they are, this doesn’t always happen. If the input shaft is sufficiently misaligned, it makes it much more difficult for the transmission to shift gears cleanly at higher engine speeds.
The most obvious example is the scenario we offered in the beginning of this story. In a four-speed manual trans, fourth gear (or any transmission with a 1:1 ratio) is achieved by connecting the input and output shafts together. Completing this gear change should be — and usually is — a simple process when all the variables are within spec. But, place the input shaft at a slight offset to the crankshaft at 7,000 rpm and the result will be a missed shift every time, because the conflicting angles will not allow the slider to make that connection.
The spec for this centerline is very precise — that large input shaft hole in the bellhousing must be within 0.006-inch of centerline. This is known as total indicated runout (TIR). There’s also a second spec, squareness, that is often overlooked, but just as important. This is where we check to make sure the face where the transmission bolts to the bellhousing is perpendicular to the engine — or at least again within 0.006-inch.
In our experience, most engines and OE bellhousings are usually within spec; although the combination we tested was 0.025-inch out. Some older steel scattershields we’ve tested had a tendency to be off center by almost 0.020-inch. If after testing the housing exceeds the limit, there is an easy way to dial it back into spec. The easiest way is to use offset dowel pins sold by Lakewood, Moroso, and a small company called McRobb Performance. The pins come in three offsets — 0.007, 0.014, and 0.021-inch. The least offset at 0.007-inch can effectively dial a wayward bellhousing that is as much as 0.020-inch out of spec. By doubling the 0.007-inch offset, this moves the bellhousing as much as 0.014-inch in one direction, which would bring a 0.020-inch offset back within the 0.006-inch limit.
Any of the offset bushings can accomplish this task, but ergonomics also play a part. The Moroso dowel pins are intentionally designed to fit loose in the block. This makes turning them in the block easier, but requires drilling a small lateral hole in the block to drill and tap for a small locking set screw that is supplied with the bushings. That’s okay if the engine is on the shop floor, but near impossible in the car. McRobb Performance offers an intelligent alternative where the offset dowel slides into place, making it easy to adjust, and then is tightened into place with an internal expanding set screw. These offset pins are not that expensive and make this job much easier.
When installing the offset dowels, be careful to install the offsets so they are oriented in the same direction. Otherwise, it will be difficult or impossible to slide the bellhousing over the dowel pins, since they will be offset in relation to each other. It’s easy to do and can make this job frustrating until you figure it out.
You will need a dial indicator and a magnetic base to perform this test, and you’ll find it takes longer to set everything up than to do the actual test. But, the effort is well worth it. Dial in that bellhousing, and those high rpm shifts will go smooth as 7,000 rpm silk.
Fanatics have plenty of factory Ford performance small blocks to choose from, but a few notable candidates come right to mind. Of course Mustang owners must recognize the original 271-hp (HiPo) 289s, though hardcore guys might bring up the very limited run of 260-hp HP-260s that predated the 289.
A hot little number, the production HiPo 289 got very close to the then-magical number of 1 (gross) horsepower per cubic inch. Once some old chicken farmer sprinkled some magic fairy dust on the motor for GT350 and Cobra use, the power output jumped to 306 hp. On paper, the Shelby version of the HiPo 289 topped the power production charts for Ford small blocks until the Boss appeared.
Though the Boss 302 was rated at just 290 hp, the larger 351 checked in with 330 hp. In reality, both Boss motors easily made more power than the 289, Shelby or otherwise. After the Boss 351 was released in 1971, power outputs took a nose dive, and we wouldn’t see any real performance small blocks from Ford until the beginning of the second muscle car era in the mid 80s.
As fondly as we remember those early performance motors, the truth is, they take a backseat to what Ford eventually introduced in the mid-late ‘80s. After the big Blue Oval introduced the 5.0L on an unsuspecting market, Ford performance no longer took a back seat to the bowtie boys. 5.0L Ford owners could hold their heads high, and, no longer had to look back longingly at early Mustang performance.
Heck, a 5.0L LX would show taillights to any small-block Shelby, to say nothing of a HiPo 289 Mustang. Things progressed rapidly after the 5.0L, as Ford brought us Tenacious Terminators, supercharged Shelbys and even killer Coyotes, but the 5.0L is the motor that started it all.
Naturally, the aftermarket stepped up in a big way to enhance the vulernable little 302. Almost overnight, a flood of high-flow, aluminum cylinder heads, powerful camshafts and trick induction systems hit the market, allowing Mustang owners to step up from stock. The result was the ability to build a street/strip terror that could easily masquerade as a daily driver.
The popularity of the 5.0L spawned an aftermarket industry, which Ford owners enjoy to this day. Using the many performance components, building a stout small block is as easy as picking up the phone. The key to the available performance is what we refer to as the power producers, namely the cylinder heads, camshaft and induction system. The after market has made great strides in the last 30 years, so it should come as no surprise that we are able to surpass the power levels of yesteryear.
While one horsepower per cubic inch was once the holy grail of power output for the production powerplants, it is now commonplace, at least for any performance street motor. In fact, if you built a performance 302 that only made 302 peak horsepower, you should consider your project somewhat less than successful, unless your build up was more of a rebuild using primarily stock components. That we can now build a 302 that exceeds the power output of the early performance (and even race) motors should not be surprising. That it can be done so easily, and with excellent street manners, is all the more impressive. Not only can a 302 be built that exceeds 370 hp, but such a motor can be ordered with no more knowledge than your credit card number.
To illustrate just how easy it is to build Ford performance, we decided to let our fingers do the typing, and placed an order to BluePrint Engines for one of their many popular Ford offerings. Though BluePrint Engines (BPE) offered everything from performance parts to complete stroker combos, we elected to go the semi-DIY route. The strokers were certainly tantalizing, but in the end, we selected a 302-based combination. The bp306sp offered 306 inches thanks to a .040 over bore.
The short block started with a production 5.0L block machined to accept a cast crank, 5.155-inch rods and hypereutectic pistons. Before you dismiss the internals for their lack of the word forged, know that we have run endless stock short blocks with similar components. The stock stuff will support impressive power, enough to actually call the strength of the block into question, but we are getting ahead of ourselves here. The assembled short block also included a hydraulic roller cam (.543/.554, 218/226 112 lsa), lifters and a front cover. Completing the bp306sp was a complete oiling system that included a production Mustang oil pan.
The BPE short block had plenty to offer, but did require a few additional components before running on the dyno. We first installed a 50-oz damper, followed by a set of cylinder heads, intake and carburetor. Since we had a BPE short block, we decided to try a set of their heads as well. The 190-cc, as-cast heads (hp9008) featured a 2.02/1.60 valve package, 60-cc combustion chambers and flow rates that topped 250 cfm on our bench.
BPE 306 Ford This is what we like to see in a hot street motor, not just plenty of peak power but a ton of torque. With over 350 lb-ft from 3,500 rpm to 5,200 rpm, the little Windsor offered a broad curve, with ample torque production, even down low. Part of the credit goes to our selection of the dual-plane intake, but the heads and cam certainly played their part. The static compression ratio of 9.5:1 meant this combination would also readily accept assistance from a power adder.
The heads were tipped by a dual-plane, Eliminator intake from Speedmaster. The polished dual plane was ideally suited for the sub-6,500 rpm combination. The final touches included a Holley 650 Ultra XP carb, MSD distributor and Hooker long-tube headers. Also present was a Meziere electric water pump, Lucas 5W-30 oil and Comp composite valve covers. Once dialed in, the BPE-headed 306 produced 371 hp at 6,100 rpm and 367 lb-ft of torque at 4,000 rpm. After assembly, the 306 combination worked perfectly and offered a broad torque curve, while the reasonable compression ratio hinted at things to come.
The only thing better than one nitrous kit is….well, you get the idea.
Words and Photos By: Richard Holdener
What can we say, sometimes you just want to go BIG! What do we mean by big? The philosophy of going big is simple. It states that if one nitrous kit is good, two must be even better. Now, while it is possible to run two nitrous kits (or stages) on a single four-barrel intake, we decided that going big for us also meant two carburetors. After all, if one carburetor is good, then two must be…well, you get the idea.
Truth be told, this all started the last time we ran a dual-quad, tunnel ram and noticed how convenient it would be to simply add not one, but a pair of plate nitrous systems to the combination. Nitrous fans will be quick to point out that it is possible to get the same amount of power from a single system, but they would be missing the point. It is possible to make plenty of power from a single turbo system, but twin turbo sounds so much better (and badder). Having a blower sticking out of the hood is always good, but what if you had a centrifugal supercharger or turbo feeding that blower? Now, you are starting to get the idea.
Given the power potential of even mild jetting on a pair of plate systems, we needed a suitable test motor capable of withstanding the extra cylinder pressure. Lucky for us, we had just such a motor sitting around just begging to be used. Nicknamed the Magnificent LS7, the 427 LSX was plenty stout thanks to the serious components used in the original build up.
The 7.0L stroker started out life as a simple LSX block from Gandrud Chevrolet. After machining, the iron race block was treated to forged internals that included a Lunati Voodoo crank, Bullet-series CP (flat-top) pistons, and matching Carrillo rods. Stepping up with the cam for the LS7 was Brian Tooley Racing. Originally designed for an LS7-headed application, the Stage IV grind featured a .616/.595 lift split (with 1.7 rockers), a 247/258-degree duration split, and 112+3. COMP Cams also stepped up in a big way with hydraulic roller lifters, hardened pushrods, and a trick, aluminum front timing cover. Given the power gains involved with nitrous, we made sure to include ARP head studs and Fel Pro MLS head gaskets in the build.
A stout short block is all good, but there were plenty of additional components used on the 427, like the complete Moroso oiling system. The Moroso components included a dedicated pan, pick up, and windage tray, along with a remote oil filter that ensured adequate delivery of the Lucas 5W-20 oil from the HV oil pump. Finishing off the short block was an ATI Super Damper, while the induction system consisted of Gen X 245 heads from TFS topped by a dual-quad, Holley Hi Ram. Using the dual-quad top on the Hi Ram allowed us to mount a pair of the Zex Perimeter Plates.
Continuing with the overkill theme was a pair of Holley 950 Ultra XPs. Sure, one would probably be more than sufficient at this power level, but why stop at just one? Holley also supplied the dual-quad throttle linkage, while MSD came through with their ignition controller, allowing us to dial in the timing curves for each combination (including retarding the timing for the nitrous). Finishing touches included a set of stock (LS1) rockers, 1 7/8-inch Hooker headers and a Meziere electric water pump.
Like most carbureted nitrous systems, the Zex Perimeter Plates were designed to sandwich between the carburetor and intake manifold. According to Zex, the Perimeter Plate system offered a number of other design features, including Perimeter Injection, Cryo-Sync, and Airflow Enhancement technology. The Perimeter Injection employed 24 injection points that combined nitrous and fuel to optimize atomization and distribution in the manifold. Flowing super cool nitrous (-127 degrees) through the plate effectively turned it into a Cryo-Sync (or heat isolator) to help cool the intake and carburetor. Flow of the nitrous and fuel through the plate and into the manifold also created a low-pressure zone to further enhance airflow into the motor. On paper at least, each Perimeter Plate sounded pretty effective, so we decided to install the dual kit on our 427.
Using jetting to control the nitrous and fuel flow, the Zex Dual Perimeter Plate system was adjustable from 100 to 300 hp. For this 427 LSX test, we chose to run the system at 200 hp (100 hp per plate). This was a reasonable amount for street use, especially when adhering to the recommended timing retard for this power level. According to Zex, the timing should be retarded by four degrees for each 100-hp shot, or a total of eight degrees for our dual system. To hedge our bets, we mixed in some race fuel just to be safe — we have a lot more testing in store for the LSX.
427 LSX-NA vs Zex Nitrous-(200-hp Shot) Nothing wakes up a motor like a little shot of juice. Adding the dual-plate nitrous system from Zex to the carbureted 427 LSX offered substantial power gains. Thanks to Perimeter Plate technology, the kit improved the power output of the LS stroker from 661 hp and 589 lb-ft of torque to 877 hp and 825 lb-ft. These were actually the spike numbers that occurred upon activation, but the power output increased by a nice solid 200 hp through the entire curve. Whether your combination is injected or carbureted, nitrous is flat-out awesome!
Each nitrous and fuel solenoid fed a T-fitting that supplied nitrous (or fuel) to the pair of plates. We hooked up a simple activation button on the throttle handle in the dyno control room and made sure to activate only at WOT. We also took the liberty of heating the bottle to ensure adequate bottle pressure before activation. Run in normally aspirated trim, the tunnel-rammed 427 produced 661 hp at 6,700 rpm and 589 lb-ft at 5,200 rpm. After activation of the dual Zex system, the peak numbers jumped initially to 877 hp and 825 lb-ft of torque, but eventually settled in with a solid 200 hp gain through the tested rpm range. I guess when it comes to running Zex on an LSX, twice is nice!
Big displacement engines like this 520ci Jon Kaase Boss 9 engine make building a car that accelerates briskly very easy. Even in a heavy car with an automatic will be a thrill with an engine that can make over 900 horsepower with an astonishing 700 lb-ft of torque way down in the rpm curve.
In the performance game, the talk is all about horsepower. It’s splashed across magazine covers and horsepower numbers are prominently displayed especially now when the numbers are over 1,000. It seems that we are forever being indoctrinated into believing the horsepower is the great solution. And most of the time, that’s correct. But not always. If you are building a Bonneville car or a top speed race car, then peak horsepower is a very powerful thing. But for a drag race car or even a mild street car – a big peak horsepower number is not always the best solution if you’re trying to build a car that’s quick. When we say quick, let’s define the term. In the early days of drag racing, the winner was always the guy who got there first, but they identified the strength of the run based on trap speed. In top speed racing, you are given a long run like five to seven miles to achieve terminal velocity. But in modern drag racing – you only have a quarter and sometimes only an 1/8-mile – 660 feet – to take the stripe. A quick car is one that will get there in the shortest amount of time – and that’s what we’ll dissect in this story.
We might want to define the terms we’re working with here just so there’s no confusion. Internal combustion engines are rated using two different types of power – torque and horsepower. These ratings are directly related yet different. Basically, torque is a measurement of a twisting motion – like that generated by the output of an engine’s crankshaft. This torque is expressed in pound-feet (lb-ft) so that one lb-ft is the force required to twist a shaft with one pound of effort over a one-foot radius. What this measurement doesn’t describe is the amount of time required to perform this effort. Once we introduce time into the equation, then we can define that amount of effort (torque) over a given amount of time – which in an internal combustion engine’s case is expressed in revolutions per minute (rpm). This amount of work was given the term horsepower by James Watt back in the 1700’s to compare the amount of work his improved steam engine could produce compared to the amount of work performed by a typical draft horse, which was something his customers were intimately related.
The equation that Watt created has been simplified to: Torque x RPM / 5,252 = HP
To give this an example, let’s say our engine makes 300 lb-ft of torque. At 3,000 rpm this means the engine is only making 171 horsepower (300 x 3,000 / 5,252 = 171). However, if we add performance parts to our engine and spin it a little faster, it is capable of making that same 300 lb-ft of torque at 6,000 rpm. By doubling the rpm at which the engine can make power – we now have a more powerful engine making 342 or twice the horsepower. The reason for this doubling of horsepower is that the engine is making the same torque in exactly half the time of the first engine – 6,000 instead of 3,000 rpm. Given the choice, most hot rodders would choose the more powerful engine. But in the performance world, things get a bit more complicated.
The reason that large displacement engines are so popular with performance enthusiasts is that as displacement increases, so does the ability for the engine to make more torque at lower engine speeds. Which is why hot rodders love big engines. A typical performance V8 engine can make 1.2 to 1.25 lb-ft of torque per cubic inch of displacement. For a 300ci engine, 300 x 1.25 = 375 lb-ft of torque, which for a pump gas street engine is a decent torque number. But now let’s apply that same 1.25 lb-ft per cubic inch plan to a 520ci big-block Ford and suddenly the numbers become a bit more Kong-like: 520 x 1.25 = 650 lb-ft of torque. This is no secret and also just puts numbers to what hot rodders have known for years – big engines make big torque.
Torque is what really moves the car, but it gets lost in the bench racing sessions when everybody only wants to talk about horsepower. But let’s go back a bit and look at engines like the Buick and Pontiac 455 ci engines. They made great torque but because of their limited cylinder head size and greater internal friction from long strokes, these larger displacement engines were not as efficient in terms of horsepower per cubic inch. There are exceptions of course, like 500ci NHRA Pro Stock engines that spin to 10,000-plus rpm and make upwards of 1,400 horsepower. At 2.8 hp/ci, these normally aspirated monsters are exceptional, but also somewhat peaky, engines. What this means is that race engines like these tend to have relatively narrow power bands where all the power is concentrated in a range of 1,000 to 1,200 rpm. We’ll define this power band as the rpm spread between peak torque and peak horsepower. A common problem with race engines is that escalating horsepower and rpm are accompanied by an increasingly narrow rpm range where the engine really makes its power.
This also occurs with street engines. Making power with any internal combustion engine is a compromise between torque and horsepower. The search for additional horsepower for a normally aspirated engine follows the path of the horsepower equation. The equation tells us that if you make the same amount of torque at a higher engine speed, you will make more horsepower. For most engines, in order to make more peak power, a longer duration cam will push the peak torque point higher in the rpm curve. Combine that longer duration with larger intake and exhaust port cylinder heads, a short runner length intake manifold, and large tube headers and you have the makings of an engine that can deliver serious horsepower. But all these components also contribute to shifting the engine’s power band to a higher engine speed. A common power band spread will be 1,500 to 1,700 rpm. In some exceptional cases, this can expand to as much as 2,000 rpm, but that’s rare. In the quest for more normally aspirated power, longer cam duration and bigger heads generally narrow the power band to 1,000 rpm and the longer duration pushes the horsepower peak to much a higher engine speeds. In order to take advantage of the higher rpm power, this most often is solved by adding a deeper (numerically higher) rear end gear.
Street-driven cars usually don’t have the luxury of running a 4.56:1 or 4.88:1 gear ratio. Narrowing the power band also places greater attention on maintaining the engine speed within this limited area. This is where additional gears in the transmission really help. So in the case of a Competition Eliminator car powered by a high horsepower engine with a narrow power band, this could call for a five-speed manual transmission instead of a four speed. The additional gear reduces the rpm drop between gears which will maintain the engine within its power band with the result being the car is now a tenth or perhaps two-tenths quicker. Even the OE’s have picked up on this effect. Note that as engines become smaller, with higher specific output, they generate less torque. To make up for this lack of torque, the OE’s have been adding more and more gear ratios to their transmissions. Chrysler, for example, currently has an eight-speed automatic transmission. The reasoning behind this increase in ratios is to maintain the rpm within a given rpm range where the engine makes power.
The difficulty with street-driven cars is that they are often compromised by the demand for more street-oriented rear gear ratios and limited to three- or four-speed automatic transmissions. An overdrive transmission can help by allowing the use of a deeper rear gear to help acceleration, but the overall limitations still apply. This brings us back to the question that every performance enthusiast needs to investigate if he is interested in improving acceleration. We’ll use the drag strip as our evaluation criterion for power improvements and what you’ll discover might change the way you think about adding power and where you should place your efforts so that it will do the most good.
Let’s use an example to illustrate the point. We put a 355ci small-block Chevy on the dyno and compared the power produced by a single plane versus a dual plane intake manifold. We equipped our engine with a classic combination of a set of Edelbrock aluminum heads combined with a mild COMP Cams hydraulic flat tappet 268 Xtreme Energy camshaft with 224/230 degrees of duration and 0.477/0.480-inch valve lift with a 110-degree lobe separation angle. Along with a set of headers and a 750 cfm Holley carburetor, this engine could be considered the prototypical street small-block. The two intakes we tested were the Edelbrock Performer RPM dual plane compared against the Edelbrock Victor, Jr single plane.
Besides the usual e.t. and speed results, the Quarter, Pro program also includes an interesting option called an RPM histogram. This chart reveals the amount of time the engine spends at various rpm points. This chart reveals very valuable information. For example, according to this graph this engine spends much of its time between 4,600 and 5,600 rpm. Armed with that information, it would seem like a good idea to concentrate on improvements in that rpm area because the power will deliver the greatest benefit.
We ran both intake manifolds across this engine and recorded the torque and horsepower curves. Many engine guys will naturally look at the horsepower peaks and quickly make a judgment based on the higher horsepower number. In this case, the Victor, Jr. intake was worth 401 peak horsepower versus 398 for the dual plane. But when we plot both torque and horsepower curves on a graph, it becomes obvious very quickly that while the Victor, Jr. did out-horsepower the Performer RPM, the dual plane was clearly better at making torque – especially between 3,000 and 4,900 rpm. In this range, the dual plane made as much as 39 lb-ft of torque more than the single plane intake. That’s a huge gain in torque and something you would certainly feel in the seat of your pants when the throttle is planted firmly to the floor.
This graph and chart plot the power comparison of our small-block Chevy dual plane vs the single plane intake. Note the major torque improvements of the dual plane over the single plane below 5,000 rpm. For a mild street car, it’s clear that the dual plane is the better choice even though it loses as much as 22 hp to the single plane at the top.
We plugged these two power curves into the Quarter, Pro drag strip simulation program. This program was originally designed by Patrick Hale and it has become our favorite drag strip simulation program. Once we added the two different power curves into the program, it was easy to compare the differences in the projected acceleration rates. By now you’ve probably already figured out that the dual plane’s torque curve delivered much stronger acceleration. While the dual plane was worth as much as 39 lb-ft, the overall average was closer to 19 lb-ft of torque but that was enough to push our simulated Chevelle to run 0.15-second quicker and 1.4 mph faster. The numbers came out to a 12.33 at 108.80 for the single plane intake while the dual plane was quicker with a 12.18 at 110.20 mph.
The reason for the dual plane’s quicker elapsed time is its superior average torque. However, the reason for the quicker quarter-mile e.t. has as much to do with our test car as it does with the engine’s additional torque. This is an important point that is often lost when doing comparisons. In this case, we are using a relatively heavy 3,600- pound Chevelle with a three-speed automatic, a conservative 3.31:1 rear gear ratio, and a tight torque converter. If we were to plug these same comparisons into a lighter and smaller ’32 Ford coupe with a four-speed manual trans, deeper 4.10:1 gears, and big tires, the added torque from the dual plane would still be quicker, but the differential would not be as great. Let’s look at why this is.
We chose to make the ’32 Ford to weigh only 2,800 pounds, which will instantly improve acceleration but the real reason that the improvement wasn’t as great is because we changed the transmission. This has less to do with the type of transmission – converting from an automatic to a manual – and more to do with the reduced gear spread. By adding another gear (from three speeds to four), this reduced the rpm drop between gears, which narrows the engine’s operating rpm after it is launched. The Quarter simulation program gives us the rpm drops with each gear changed. Rather than go through all the numbers, let’s look at average rpm drop.
For the automatic, the average drop in rpm (using TH400 transmission ratios) was 2,140 rpm. Using a TR-6060 manual transmission (only the first four gears) this delivered an average rpm drop of only 1,630 rpm. The reduced rpm drop delivered by the manual trans keeps the average rpm 510 rpm higher at the completion of the shift. By nature, this will increase the average time spend at higher engine speeds. This tends to help the engine with more power at the higher engine speeds. But our simulation shows that leaving at around 3,000 rpm, the engine with the higher average torque in the middle still accelerates quicker.
As you can see with these examples, average torque is a much better way to evaluate an engine’s performance than just using peak horsepower. As we’ve mentioned earlier, these examples are all aimed at a typical street car – not a dedicated drag car. In the case of a dedicated drag car, the power band will tend to dictate the type of transmission used. So with a narrow power band, a manual trans with more gears is a good idea. In the case of a class legal car where a two-speed automatic transmission (like a Powerglide) is required by the rules, this would dictate building an engine with a wider power band in order to compensate for that huge rpm drop. Actually, from what we hear, some Powerglide racers use a very loose converter to keep the engine speed high even after the shift.
To condense this down to its logical conclusion, if performance and acceleration are the primary goal, then the street car builder has essentially three approaches. The first is to build the drivetrain around the engine’s power curve to optimize performance. The second is to build the engine to take advantage of the car’s existing drivetrain. The third option is where most projects exist – they optimize the engine as best as possible within the limitations of the current drivetrain. From this starting point, the builder can begin to approach the way the car needs to be constructed. If your plans call for a heavy car with an automatic transmission and a relatively tight torque converter, the ideal engine would be a large displacement engine or a possibly a small-block with a positive displacement supercharger than will make lots of low-speed torque. Or, if you really want to build a high-winding, small displacement engine that will spin to 7,500 rpm, an engine like that would be best served in a lightweight body style or perhaps a street rod equipped with a manual transmission – preferably with a deep rear gear ratio to keep the engine in the rpm range where it can make its power. Another example for that high rpm small-block might be open road race top speed car where you can choose a rear axle gear ratio and tire size that will put the peak horsepower rpm at or near the vehicle’s top speed potential.
Gear Ratios
The following is a comparison of the Chrysler 8-speed automatic versus the old school three-speed 727 Torqueflite. We list the ratios as well as the percentage of rpm drop between shifts. As the number of ratios increase, the rpm drop between gears decreases, maintaining the engine speed within a narrower power band. The additional gears also allow a much deeper First gear as evidenced by the 4.71:1 First gear in the eight-speed. Also note how Third gear in the eight-speed is nearly the same ratio as First gear in the 727.
The opposite effect is what many drag cars with very high torque and horsepower engines are using. For example, the Rossler TH-210 refers to a 2.10:1 First gear ratio in a TH-400 transmission that reduces the amount of torque multiplication over the tires. With a 2,500 horsepower engine, you don’t want to multiply the torque yet you still need a decent gear ratio to help launch the car. Second gear is around 1.30:1 which splits the difference between First and Third gear. This is still better than using a Powerglide with its large rpm drop between First and High gears.
Conclusion
None of the material presented here is shockingly new. But sometimes the proper approach can get lost in a world of hype and hyperbole. Building an engine with lots of peak horsepower will always be something to use as a goal, just don’t forget about the torque that gets you there in the first place.
Class legal cars like the SAM Racing 2012 (updated to 2014 body specs) runs a CC/Stock Automatic class legal LS7-based 427 with an A-1 TH3350 trans and converter. The Camaro, driven by Brian Massingill, has run a best of 9.14 at 145 mph and it gets there on a very strong torque curve combined with excellent peak horsepower – none of which the SAM folks are willing to divulge!
Before we start adding boost, it is important to point out that your transmission will affect the power output of your Mustang (measured at the wheels). An automatic will register roughly 30 hp less than a manual transmission.
Here is a statement Camaro owners already know, the 2015-16 Mustang is a force to the reckoned with. Despite the apparent lack of displacement (compared to the competition), the “little” 5.0L makes up for its size deficiency with terabits of technology, including DOHC cylinder heads, four valves per cylinder and variable cam timing. This technological combination allows the 5.0L motor to offer the torque curve of a 6.0L, to say nothing of impressive rpm potential. As good as the stock Coyote Mustang is, who among us doesn’t want even more performance?
Luckily enthusiasts need look no further than Kenne Bell to satisfy all their power needs, in one simply bolt on no less. The great thing about the Kenne Bell twin-screw supercharger kit is the amazing flexibility. As if the ability of the standard kit to add over 200 hp to your Coyote isn’t enough, additional boost can more than double those gains. Still not enough? The standard 2.8L is capable of supporting over 1,000 hp, but Kenne Bell offers even larger superchargers capable of exceeding 2,000 hp!
Before getting to the supercharger testing, it is important to understand why some 5.0L Coyote Mustangs register different power readings than others. Three critical factors that ultimately affect the measured wheel power output of the Coyote Mustang (actually all vehicles) include transmission, rear end type, and gearing. Extensive dyno testing has revealed that (despite the same motor output), a Mustang equipped with an automatic transmission will register a lower wheel power output than a manual transmission. There is more power loss (roughly 30 hp) through the automatic than the manual. Likewise for the new independent rear suspension, as the IRS will lose nearly 15 hp compared to a solid-axle Coyote. The final variable is the internal gearing in the rear end. Though it might improve acceleration, a higher numerical gear (3.73) will show less wheel hp than a lower numerical gear set (3.55, 3.27, 3.08 etc…). It is important to understand these variables as the change in power offered by these components will carry over to the supercharged outputs, and can make it difficult to compare early and late Coyote power outputs.
We touched on the different displacement superchargers offered by Kenne Bell, but the effectiveness of the twin-screw supercharger is a function of more than just sizing. The Kenne Bell supercharger is chock full of technology, including things like billet casing, an industry leading 6×4 rotor pack and Liquid Cooling. The strength of the external case is critical as improved case strength allows for tighter critical tolerances. These tolerances allow improved flow rates and boost potential through increased rotor speed. The case strength is then combined with the 4×6 rotor pack to further improve power while reducing inlet air temps.
Additional efficiency for the system comes from Liquid Cooling. Not to be confused with the air-to-water intercooler supplied with the kit, the Liquid Cooling system was designed to equalize the sizable temperature differential between the cold (inlet) and hot (discharge) sides of the supercharger. This temperature differential causes changes in tolerances on the hot and cold ends of the supercharger to eliminate high-rpm rotor scuffing common with other positive displacement superchargers. Kenne Bell designed the Liquid Cooling to minimize this temperature differential and to improve longevity of their superchargers.
One final word here before getting to the test results. A supercharger is only as good as the inlet system feeding it. Restrict the inlet system and you literally choke off the power and boost capability of even the most efficient supercharger. Obviously Kenne Bell recognized this long ago, as they have gone to great lengths to super size every component of their induction system. Included in the Kenne Bell inlet arsenal are the manifold, throttle body, MAF, and air intake. Starting with the restrictive factory air box, Kenne Bell designed a massive 4.5-inch, cold-air inlet, and MAF system (flowing 2,000 cfm). Naturally resizing (and repositioning) the MAF necessitated recalibration of the ECU, but the supplied supercharger program included the necessary changes. Finishing up the high-flow induction system, the Kenne Bell Mammoth intake was designed to accept the 168mm oval throttle body capable of flowing 2,150 cfm! Racers needing even more flow for a larger supercharger can always step up to the dual 106mm BIGUN throttle body assembly.
Technology and potential are all well and good, but how do they translate to real-world power numbers? To find out, we applied a Kenne Bell supercharger kit to a 2015 Mustang GT. Run on the Dynojet chassis dyno, the 2015 5.0L (manual trans) GT Mustang produced 381 hp and 378 lb-ft of torque at the wheels. After installation of the 50-state kit, featuring the 2.8L, twin-screw supercharger (at 10 psi), the peak numbers jumped to 620 hp and 507 lb-ft of torque (a 50-state kit is pending). Kenne Bell twin For The Win! Need more? Kenne Bell then added 130-pound Injector Dynamic injectors and 20V Boost-A-Pump (using the stock pumps) and cranked up the boost to 21 psi. The result was an impressive 843 hp. Remember, this was with standard 2.8L supercharger and no internal changes to the stock 5.0L Coyote motor. One of Kenne Bell’s customers managed nearly 950 wheel hp (on a Mustang Dyno) running E85 fuel on the stock motor. This combination was used to exceed 200 mph in the standing mile.
The stock 5.0L Coyote was no slouch, pumping out 385 hp and 378 lb-ft in normally aspirated trim. After installation of the Kenne Bell supercharger kit, this jumped to 620 hp and 507 lb-ft of torque at 11 psi (93 octane). Kenne Bell has exceeded 840 hp on the stock motor using race fuel, a Boost-a-Pump and larger injectors.
Why install a supercharger on a motor already equipped with one? The answer is easy! A Kenne Bell blower upgrade is a tried and true method for improving the power output of the 5.4L (and 5.8L) GT500 modular Ford motor. We all know that the Shelby GT500 is an impressive piece, especially with the most recent 5.8L 4-valve motor. Even with the previous (and smaller) 5.4L, the GT500 was a forced to be reckoned with on the street. Despite the presence of a factory supercharger and impressive power offered in stock trim, the supercharger itself was the limiting factory when it came to additional power. Superchargers are designed for specific power levels. There is obviously wiggle room in their ability, but eventually, the physical size and rpm potential of the blower limits that amount of airflow it can provide. The factory-supplied Eaton supercharger supplied on the GT500 is no different, so making big power gains means steeping up to not only bigger, but Better Boost!
The test mule was a bone-stock, 5.4L four-valve pulled from a 2011 GT500.
To illustrate the potential of Better Boost, we performed a blower upgrade on an otherwise stock 2011 GT500 motor. While most GT500 testing is performed on the chassis dyno, our testing was run with the motor out of the car on the engine dyno. This made working on the engine much easier, though a Kenne Bell, twin-screw blower upgrade is not terribly difficult in the car.
Compared to the stock M122 Eaton supercharger, the Kenne Bell offered both improved efficiency and increased displacement. That’s why Shelby chose them for the Super Snake and 1000 horsepower programs. The additional efficiency came first from the twin-screw design (already superior to traditional roots) but Kenne Bell kicked things up another notch by employing an industry-leading 4×6 twin-screw rotor pack. The result of this design was that the Kenne Bell twin-screw blower offered increased power with less parasitic losses and a lower inlet air temp than the Eaton supercharger. Toss in the displacement hike to 2.8 liters and you get a blower capable of supporting over 1,000 horsepower on the right application.
The theories were all well and good on paper, but how would they translate into real-world numbers? To find out, we installed the GT500 motor on the dyno for testing. Rather than run the factory ECU, the timing and fuel were controlled using a FAST XFI/XIM management system. To demonstrate just how much power the factory Eaton supercharger was contributing to the mix, we ran the GT500 motor first in normally aspirated trim using a modified 5.4L Cobra R intake. We combined the Cobra R lower intake with a fabricated plenum and Accufab throttle body. Remember, with the mild factory cam timing and lower compression, this GT500 motor was designed specifically for forced-induction use. Equipped with the Cobra R intake and stock exhaust manifolds, the normally aspirated GT500 motor produced 384 hp at 5,300 rpm and 413 lb-ft of torque at 4,400 rpm. That the motor produced more torque than horsepower is a clear indication of the mild cam timing. Having established our baseline, it was time for boost.
After the installation of the factory Eaton supercharger and air-to-water intercooler (using dyno water), we run the supercharged combination using the factory 3.06-inch blower pulley. Once again run through the factory cast-iron exhaust manifolds, the supercharger pumped out a maximum of 10 psi of boost and elevated the power output from 384 hp and 413 lb-ft of torque to 594 hp and 559 lb-ft of torque. The difference between this output and the factory rated 550 hp can be attributed to the lack of an air intake, complete exhaust and drive accessories.
The optimized tune no doubt added a few extra ponies as well, as the factory tune was very conservative. Two things the positive displacement (roots-style) blowers excel at are immediate boost and torque production. Though peak numbers are usually the hot topic of discussion, the broad torque curve (exceeding 500 lb-ft from below 3,000 rpm past 6,000 rpm) offered by the supercharged 5.4L is what really helps accelerate the GT500. There was obviously more boost and power to be had from the Eaton supercharger, but we decided to step up not just to more boost, but Better Boost with the Kenne Bell blower upgrade.
To illustrate the substantial power gains offered by the increased efficiency and displacement, we configured the Kenne Bell twin-screw supercharger with the same size blower pulley as the factory Eaton. Both combos were run with the factory crank pulley. The closest we could get to the 3.06-inch stock GT500 blower pulley was a 3.0-inch Kenne Bell version. The Kenne Bell blower upgrade utilized a new lower intake that accepted the factory GT500 air-to-water intercooler. Installation of the 2.8L blower upgrade was simple, easy, and well worth the effort given the dramatic results. Run with the 3.0-inch blower pulley, the Kenne Bell supercharger pumped out 20.0 psi of boost.
This represented an increase of 10 psi over the factory Eaton. Naturally the additional boost increased the power output, jumping from 594 hp and 559 lb-ft of torque to 806 hp and 721 lb-ft. The final test involved replacing the stock exhaust manifolds with 1 7/8-inch long-tube headers. The headers further increased the power output of the Kenne Bell 5.4L to 823 hp and 731 lb-ft, while simultaneously dropping the boost by almost 1 full pound. More power with less pressure is a little something we like to call Better Boost!
Before running our tests on the blower upgrade, we decided it was a good idea to run the otherwise stock GT500 motor normally aspirated. This way we could demonstrate just how much of the power came from boost supplied by the stock blower. Run with a modified Cobra R intake system, the GT500 motor produced 384 hp and 413 lb-ft of torque. After adding the Eaton supercharger, these numbers jumped to 594 hp and 559 lb-ft of torque. Stepping up to the Kenne Bell 2.8L, twin-screw supercharger resulted in 806 hp and 721 lb-ft of torque.
The initial testing was run with the factory cast-iron exhaust manifolds, but we eventually upgraded with motor with a pair of 1 7/8-inch, long-tube headers from American Racing. The headers were worth a decent power gain, as the peak numbers jumped from 806 hp and 721 lb-ft to 823 hp and 731 lb-ft. Boost also dropped by nearly 1 full psi, from 20.0 psi to 19.1 psi.
There’s no denying that the new GM LS, Chrysler Gen III hemi, and Ford Mod motors have carved a healthy niche in the pantheon of performance engines. While the power is there for the making and taking, these new engines also demand new ways of accomplishing standard practices. For example, how do you pressure-lube one of these new-gen engines when the oil pump is driven off the crankshaft?
Let’s say you’ve just bought a brand new LS3 or perhaps a new Mopar 6.1L hemi crate engine. Accepted engine protocol demands that any new or long-dormant engine be treated to fresh, pressurized oil pushed through all bearings and wear surfaces before the engine fires for the first time.
The problem is today’s modern engines don’t use a distributor and the oil pump is driven directly off the crank so there’s no way to externally spin the oil pump. A classic internet forum remedy is to “Yank and Crank”. This means pulling the spark plugs and cranking the engine with the starter motor and hoping the oil pump will pressurize the engine. The problem is that the pickup in the oil pan is a long distance from the crank-mounted oil pump. The starter motor’s cranking speed is often too slow to prime the pump so no oil pressure is created. Plus, spinning a new engine with dry main and rod bearings is exactly what you don’t want to do if you prefer to treat your engine with respect.
One solution is a sealed, external oil reservoir connected to the engine using 15 to 20 psi air pressure to push the oil into the engine. While this idea works, especially if you pre-fill the oil filter first, this pushes oil generally through just the main and rod bearings. The limited volume and pressure will not push oil all the way up to all 16 rocker arms, which is the best indication that the entire engine has received oil.
Our plan called for a cheap but reusable oil reservoir large enough to carry 5 to 7 quarts of oil and would mount a used oil pump that could be driven by an electric drill motor. We also wanted to recirculate this oil through the engine, so we drilled out a bolt that matched the drain plug threads to install a -6 return line fitting connected on the other end to a -6 AN bulkhead fitting bolted to the lid of the reservoir. This allows us to run the drill motor continuously which is important because it can take 5 to perhaps 10 minutes to push enough oil through the engine to eventually lube all 16 rocker arms. We also rotate the crankshaft roughly 90 degrees at a time to ensure oil gets to all 16 rockers.
This simple, inexpensive pressure luber can be universally applied to any modern engine. While there are several different ways to approach this project, we like this idea because it is inexpensive and uses parts that are generally easy to obtain. Our parts list is comprised of a simple hardware store plastic bucket, a used small-block Chevy oil pump, a few AN fittings, and a couple lengths of hose. The only exotic tool required is a ½-inch electric drill motor. We’ve used our homemade luber on multiple LS engines and it gets the job done quickly and efficiently. Once the task is accomplished, we connect the pressure and return lines with a T fitting and wrap the bucket in a large plastic bag to keep the dust out until it’s ready for the next engine. Generally after pressure lubing two or three used engines, we dump the oil as it begins to get dirty.
Check out our plan and while our photos show it used on an LS engine. This will work equally well on Ford Mod motors and Chrysler hemi engines. If you’re creative and a good scrounger, you can probably build one for $60 and that price is based on all new hoses and AN fittings. Build one for yourself and we guarantee you’ll be popular with your friends who own late-model engines.
Why on earth would anyone want to replace the factory rocker arms on an LS application? Aren’t they already roller rockers? Aren’t they already lightweight? Haven’t they been proven effective on countless thousands of high-powered LS applications? The answer to all of these questions is yes, including the first one.
Confused? Don’t be, as the factory roller rockers employed on every LS application offer a great many positive qualities, but rest assured, there is additional power to be had with the right rocker upgrade. As with any modification, replacing the factory rockers with roller rockers might take additional hardware, like pushrods or certainly valve springs, but when you go looking for power, leave no stone unturned.
To illustrate the gains offered by upgrading the factory rockers, we ran a back-to-back test using the stock rockers and a set of 1.72-ratio, aluminum roller rockers from COMP Cams. Before getting to the test results, let’s take a look at the test motor. Rather than run the test one of the many stock LS applications, we decided to compare the rockers on a more dedicated build up. Starting with an aluminum 5.7L block, we proceeded to stroke and poke the LS6 out to 383c.i.
The boys at L&R Automotive were responsible for the machining to accept the Speedmaster 4.0-inch stroker crank, JE forged pistons, and K1 connecting rods. Unlike stock pistons, the JE forgings featured valve reliefs to allow use of high-lift (long duration) cam profiles. In addition to the new rings and bearings, Fel Pro also came through with a new oil pump, timing chain, and MLS head gaskets.
Use of the 4.00-inch stroker crank meant it was necessary to shim and clearance the factory windage tray using washers and a small mallet. Minor machining on the bottom of the cylinder bore (for rod bolt clearance) was necessary with this stroker assembly. With a stout short block at the ready, it was time to make some power.
First on the To Do list was the proper camshaft. With power and drivability in mind, we selected an off-the-shelf grind from COMP Cams. Though we were running cathedral-port heads, we made our selection from the many rec-port offerings from COMP.
The 281LRR HR13 (pt# 54-461-11) featured a healthy .617/.624 lift split, a 231/247-degree duration split, and 113-degree lsa. COMP Cams also supplied a new set of hydraulic roller lifters (pt# 850-16), a set of Magnum pushrods (7.45 inches in length), and the required aluminum roller rockers for the test.
The combination of displacement and our power producers (heads, cam, and intake) combined to produce peak power numbers near 6,500 rpm. The high-lift cam allowed the engine to take full advantage of the flow offered by ported heads, while the duration figures made the sucker rev.
Working with the COMP cam was a set of 243 LS6 cylinder heads. To maximize the flow rate of the factory castings, the heads were shipped off to Total Engine Airflow (TEA) for their Stage 2 porting. The procedure included CNC porting of the intake, exhaust, and combustion chamber, revised valve sizing and a new spring package. The CNC procedure resulted in intake port volumes of 225cc.
When combined with the new 2.04-inch stainless steel valves and the CNC chamber work, the results were peak intake flow numbers of 328 cfm at just .600 lift. The exhaust flow was equally impressive through the new 1.57-inch valves, at 270 cfm. More than just peak numbers, the TEA Stage 2 package significantly improved the flow rate of the stock castings through the entire lift range, which is what really makes power.
The final touch on the TEA LS6 heads was a dual valve-spring package combined with titanium retainers. The springs offered enough seat and open pressure, coil-bind, and retainer-to-seal clearance to run cams with as much as .650 lift (perfect for our cam choice). The springs were also sufficient for use with the 1.72-ratio, aluminum roller rockers.
The final power producer employed on the aluminum stroker test motor was a 10mm, LSXRT composite intake manifold from FAST. To maximize flow to the motor, the intake was teamed with one of their massive 102mm Big-Mouth throttle bodies. The intake combo was fed by a set of billet fuel rails and 42-pound injectors, all from FAST. Finishing touches on the LS6 stroker included the factory coil packs, a FAST XFI/XIM management system, and a set of 1 7/8-inch stainless steel headers from American Racing (with 18-inch collector extensions).
Prior to start up, the pan was filled with 5W-30 Lucas Oil, and the motor was spun using the starter until oil pressure was visible on the gauge. Once started, the motor was treated to a pair of computer-controlled break-in cycles before running our rocker test. Equipped with the stock rockers, the 383 stroke produced repeatable runs of 578 hp at 6,500 rpm and 542 lb-ft of torque at 4,700 rpm.
After running the stock rockers, it was time to upgrade to the COMP units. For rockers, we chose a set of bolt-down, COMP Ultra-Gold Arc Series rockers (pt# 19024-16). The rockers offered ease of installation (simple bolt-down replacement), a 1.72:1 rocker ratio to slightly increase lift (stock LS was 1.7), and extra strong, CNC-extruded rocker bodies that featured billet trunnions with captured needle bearings. Toss in a roller tip to replace the friction-robbing, factory slider tip and you have the makings of a serious rocker upgrade.
The rocker swap was a simple bolt-down affair using the supplied rocker stands to replace the factory unit. Once installed, we ran the 383 stroker and were immediately rewarded with additional power. The roller rocker upgrade increased the peak power output to 588 hp at 6,400 rpm, but peak torque checked in at 541 lb-ft at 4,800 rpm.
The rockers offered additional power only above 5,300 rpm, with no change in the curve below that porting. It should be pointed out that the extra weight of the rockers will require sufficient spring pressure, but our TEA heads were already equipped for the test. If you are looking for more power, you might try getting off those stock rockers and going roller!
Understanding what it takes to sand, cut, and polish
By Cam Benty
There are plenty of abrasive discussions that color one’s life. For purposes of this discussion, we will stick with things that are really abrasive — as in cutting wheels, sanding, and grinding. While these may seem like simple tasks, there is a fair amount of technology going on with abrasives these days. Whether you are simply cutting through old paint, smoothing metal surfaces, or cutting through sheetmetal, there are plenty of helpful products that can make your life far easier.
The folks at 3M recently gave us a run through of their latest products, proving once again they know plenty about things that affect automotive types, and their pursuit of finish perfection.
With regards to sanding discs, 3M offers four different levels of abrasives, dependent on your requirements and depth of your pockets. From aluminum oxide all the way up to the precision shaped grain for Cubitron II, each material is the best in its class for its performance and value. Lucky for us, they are color coded for easy differentiation.
Red — aluminum oxide
Comprehensive line of economical abrasives. Best in class performance. Made with aluminum oxide.
Yellow & Green — premium aluminum oxide
Full line of standard and course grade abrasives that mix quality minerals and precision coating to deliver quality performance and improved life. Made with premium aluminum oxide and crushed ceramic.
Silver — crushed ceramic
Synthetic material that is tougher than aluminum oxide and silicon carbide. Ceramic grains remove material faster (and more uniformly) than naturally occurring minerals.
Light Purple — crushed ceramic
Synthetic material is tougher than aluminum oxide and silicone carbide. Ceramic grains remove material faster and more uniformly than naturally occurring minerals.
Dark Purple — precision shaped grain (Cubitron II)
Shaped ceramics that match the toughness of synthetic products and add superior triangular shape. Triangular peaks slice through material and wear evenly for fastest removal and life.
Cubitron II innovation
While aluminum oxide and crushed ceramic abrasives do a terrific job in all cutting capacities, the focus of our experience working with Mark Oja from California Speed & Custom was with the Cubitron II abrasive, top of the line due to its new and innovative technology.
During our test, we used a wide variety of air and electric tools just to get a feel for Cubitron II materials and their abilities.
This single action Sander, fitted with Cubitron II 36-grit, abrasive pad, makes quick work of the corrosion on this bar stock. As with any abrasive, regardless of the cutting action speed, keep clear of other workers or flammable materials, and wear correct personal safety gear.
With conventional ceramic abrasives, the material is glued to heavy duty, proprietary material backing paper (in case you were napping through the last five decades of paint prep, no one uses real sand for sand paper). Other than the overall grit rating, there is no order in which the materials are applied on the surface. With ceramic and aluminum oxide abrasives, there is surface heat buildup as the abrasive works. As anyone who works with abrasives knows, the abrasive eventually wears down. Time for a new disc!
Enter the Cubitron II abrasives line. The surface of this abrasive is basically a series of sharp mountains that share relatively similar pyramid-like shapes and structure. As Cubitron II is worked along the surface of the panel, the tops of these pyramids break off, creating additional sharp points that fall into the valleys and basically rejuvenate the abrasive surface. The proprietary ceramic materials used in Cubitron II cut 30 percent faster than conventional ceramics, due to the shape of the ceramic materials.
This ever-changing landscape also allows twice the amount of cutting time per abrasive. In addition, it operates cooler than standard ceramic products, reducing the surface heat and, thus, the chance of panel warpage.
As you would expect, Cubitron II is available for a wide variety of grits — from 36 to 80 for grinding, 40 to 220 discs for a Dual Action sander — allowing you to select the right one for the job, from 36 to 80 for grinding to 40 to 220 discs for a Dual Action sander. Cubitron II Cut Off Wheels are available in 3- and 4-inch diameters, while 3M Hookit File Sheets range from 40 to 220 grit. File Belt grits feature three grits: 36, 60, and 80.
Tools of the grinding trade
The right tool for the job is always a good motto for grinding, cutting, and polishing. The following list of 3M tools are built to take advantage of the abrasives outlined earlier.
Disc Sander
Designed to work with coated and surface conditioning discs with MOS Ratings of 18,000 rpm or greater
Removable side handle furnished with tool
3M Gripping Material molded into tool housing for greater operator comfort
Right angle steel gear head with grease fitting for increased gear life
Rear exhaust
File Belt Sander
This air-powered sander is lightweight, durable, and constructed with the operator’s comfort and efficiency in mind
Grind and blend from contact wheel or platen
Available in ½x18-inch and 3/8×13-inch belt widths
Both belt housing/guard and handle rotate to easily get into hard-to-reach areas and maximize user comfort
Operates at up to 17,000 rpm
Cut-Off Wheel Tool
Cut-OFF Wheel Tools can deliver fast, smooth performance (up to 25,000 rpm).
These 1 HP tools have the power to cut through carbon steel, stainless steel, and other materials.
Compact design with built-in safety features for easy handling.
3M Gripping Material molded into tool housing for greater operator comfort.
A collection of tricks, shortcuts, and helpful hints aimed at easing the automotive execution of ‘necessary’ modifications
Words and Photos: Jeff Smith
There’s really no better way to learn how to work on cars than by just diving in and turning the wrenches yourself. We make mistakes along the way, but learn some valuable lessons, too. Social media likes to share lots of information, but most of it is pretty tame stuff. So, we’re starting this off as our own version of a tweet or a post that lists some of the cool stuff we’ve learned in the past year.
Not all of these will apply to every reader, but frankly, one good tech tip from a friend that will help save time, money, or aggravation is worth the small amount of effort it takes to read through this collection of tips. If only one of these helps you through a difficult process or saves you some grief, then we’ve done our job.
If you have any tips to add to our catalog, give us a shout on our Facebook page: facebook.com/PPNDigital.
1. Simple Holley carb fix
In the last few years, we’ve noticed a problem with a few of our Holley carbs that sometimes sit around the shop for months before they are used again. In that time, the standard black accelerator pump diaphragm becomes brittle and must be replaced. You can replace it with an identical item from Holley, but your problem will likely reoccur if the car sits for a long period of time.
A better idea is to spend a little more money on Holley’s green Viton rubber diaphragm. The 30cc diaphragm is PN 135-10 and costs $9.89. It’s roughly three times the cost of the standard diaphragm, but it will last for as long as you’ll likely own the carburetor, so it’s worth the investment.
2. It’s permanent
A popular conversion for the older GM starter motors is to use the Ford relay and place a shunt or heavy wire between the starter and battery terminals on the GM solenoid. This works okay with the old starters, but this is not good with permanent magnet starter motors. Once any electric motor begins to spin, it becomes an electric generator, as well.
With a shunt or connector between the solenoid and the starter motor, the permanent magnet starters will continue to crank after the start key is released — because even this small current will keep the hold-in side of the solenoid engaged — and the starter will not release even after the engine starts.
This will quickly damage the starter motor if allowed to continue. Wire any permanent magnet starter with the stock-style wiring, and it will work perfectly.
3. Bad connection
Don’t gang the power leads to the positive side of the battery. Not only does it look cheesy, but if you are using an EFI or digital controller for an electronic automatic trans, this could potentially contribute to erratic EFI operation.
Move the other power leads to a remotely-mounted power terminal and only connect the EFI main power lead to the battery. This will leave only two leads (other than the starter motor cable) to the battery. This is when a dual connection battery (top and side) is a nice addition.
Your digital EFI will be eternally grateful and reward you with better and more predictable performance. Always run the EFI ground directly to the battery, as well.
4. Burp it
Liquid-filled pressure gauges are nice — they are more stable than standard gauges — but beware of the hidden hiccup. These gauges are subject to errors when exposed to high temperatures. This isn’t a concern with high-pressure gauges, such as nitrous bottle pressure. But with a liquid-filled fuel gauge reading single-digit carburetor fuel pressure, always “burp” the gauge before using it. This releases any built-up pressure inside the gauge from the hot liquid.
All liquid-filled gauges have a small rubber stopper near the top of the gauge. With the gauge sitting upright, slightly lift one corner of the stopper; this should release any pressure. We do this every time before we use our ZEX nitrous fuel-pressure gauge to ensure accurate readings.
We had a learning session where we discovered even a 0.5 psi build-up of pressure will affect the gauge accuracy by that same amount. If you’re tuning nitrous with fuel pressure, a half-psi of error at 5 psi is a 10-percent error factor, which is unacceptable.
5. 10 – 10 x 3
This is COMP Cams’ new recommended break-in procedure for flat tappet or hydraulic roller cam engines. Run the engine for 10 minutes at 1,500 to 2,000 rpm and then stop and cool it down for 10 minutes. Then, run the engine again for 10 minutes, and repeat this three times, for a total running time of 30 minutes. The whole process will require an hour and keeps the oil temperature lower overall.
For race engines, it’s best to start with lower, break-in ratio rocker ratios (like 1.2:1) and remove the inner valve spring for the first session. Re-install the inner springs for the second session, and finally, the rockers you will be running for the third session. This gradually builds up the load on the rollers and the cam. Don’t forget to use a high-quality break-in oil, like COMP’s ZDDP-enhanced line or Driven Racing Oil (which COMP now sells).
6. Take me to the pilot
Did you know there’s a wrong way to install a pilot bearing? The right way, according to Centerforce’s Will Baty, is to install the sealed end (on the right) facing the transmission. This keeps that nasty clutch dust and crud out of the bearing. It’s a good idea to add a little more grease to the existing bearing, since it comes with only a small amount. Good wheel bearing grease is acceptable.
As for pilot bushings, the Oilite bushings should not be lubed, as they are self-lubricating. This design pulls lube out of the material to the surface of the pilot, through open pores, when heated. Adding lube to these bushings will seal up the pores and eventually seize the bushing onto the shaft. An Oilite bushing can be easily identified because it is not magnetic.
7. MSD backup
Here’s the scenario. Your MSD ignition box fails, and you’re left stranded on the side of the road. While carrying around a spare MSD is the simplest way to avoid this, there’s a cheaper and less intrusive alternative.
All MSD distributors use a magnetic pickup to trigger the MSD box. This is the same style pickup used in an HEI, as well as Ford and Chrysler electronic distributors. Mount an HEI module to a small aluminum plate to act as a heat sink, then wiring it is as simple as hooking the violet wire from the distributor to the HEI “G” pin and the orange lead from the MSD to the “W,” or signal pin, on the HEI.
The two leads on the other side of the HEI module connect to the coil. The positive side of the coil connects to the “B” terminal (battery), while the negative side of the coil hooks to the “C” terminal. You can adapt the wires from the HEI module to a MSD connector (PN 8824, $7.23 Summit Racing) to make the conversion even easier. Make sure to ground the aluminum plate and use some thermal heat transfer paste between the HEI module and the aluminum plate, and you’re ready to rock.
8. Octane booster games
When considering a typical octane booster, remember this bit of information. Most octane boosters will claim to increase the fuel octane by “three points,” as an example. Most enthusiasts think this means improving the octane, using the example, from 91 to 94.
The reality is that a point of octane is a tenth (0.10) of one octane number. So three points are equal to only 0.30 of one octane. Just be aware of what you’re buying before you lay down your hard-earned cash. This NOS octane booster label claims 7 points improvement — which is better — but it’s still less than one full octane number.
9. Torque values
Torque values for tightening a fastener will change with the lube you use. For example, Centerforce lists 82 ft.-lbs. as the torque value when using ARP flywheel bolts, but that’s if you use engine oil. If you use Ultra-Torque, the torque value drops to 60 ft.-lbs. because the lube radically reduces the friction between the underside of the bolt and the flywheel.
Generally speaking, 50 percent of the applied torque is created by friction underneath the bolt head. Reducing this friction by using the Ultra-Torque applies more torque to stretching the bolt to its required spec. So, it’s critical to understand the difference in lubes and know which one to use with which spec.
It might seem a small point, but under-torquing a fastener like the flywheel bolt might be just as bad as over-torquing it — perhaps worse when it starts vibrating and shears the bolts off at 6,000 rpm. This graph shows how using engine oil under the bolt head changes the torque value after multiple torque applications, versus how the Ultra-Torque delivers a far more stable application of torque.
10. Tic-Tic-Tic
That ticking lifter can be caused by dirt that prevents the check ball at the bottom of the lifter piston from properly closing and sealing. This allows the oil to bleed off and produces that clatter sound. This can also be caused by poor oil change habits that tend to gum up the lifter.
Sometimes, you can remove the offending lifter, disassemble it, clean the piston, and then the check ball. Edelbrock’s Curt Hooker says you can try high-zinc oil to attempt to clean the debris. We’ve also had success using a quart of ATF, which is very high-detergent oil that can help clean the lifters.
11. Dielectric grease
Very few people realize what this stuff is. Dielectric grease is designed to insulate errant voltage from escaping from the spark plug boot. The emphasis here is on how to use it. Do not just squeeze a load of this stuff into the spark plug boot.
Instead, use a cotton swab or a small straight screwdriver to apply a light coat to the inside of the plug boot. This will keep the dielectric grease away from the spark plug wire connection, where you don’t want it. This grease on the spark plug connector will attempt to insulate the connection.
12. Watching cable `
On older muscle cars, it’s best to lubricate the speedo cable every 30,000 miles or so to allow it to turn freely. If you ever see a cable that appears to have been melted, this is caused by a poor ground between the battery, engine, and the body.
During cranking, the electrical system is looking for the shortest ground or return path, and if the ground cable is bad, much of that amperage will run right through the speedometer cable, creating heat and melting the cable. The clues are there if you pay attention to them.
13. LOMA not LMAO
Many LS engines built after 2012 come with what GM calls Active Fuel Management (AFM), also known as displacement on demand (or DOD). If you plan to change the camshaft in one of these engines, you will also have to disable the AFM system.
This will require eight new non-AFM lifters, and you must also block off the oil passages in the tall stands, in the middle of the valley cover, that feed oil to the Lifter Oil Manifold Assembly (LOMA). To delete the AFM, the oil passages in the stands must be plugged to prevent massive internal oil leaks. Lingenfelter Performance Engineering sells a tool that rivets the AFM holes closed — PN L950105305 is $79.99, and extra rivets (PN L960225305) are $19.95. This is a permanent repair.
Other alternatives include drilling and tapping each stand to close with an Allen plug, which you should only do if the engine is completely apart (to prevent aluminum chips from falling into the engine). The simplest step is to use a non-AFM LS3 lifter cover — PN 12598832, $51.97 through Summit Racing. The cover offers O-rings that seal the top of the stands and prevent oil from escaping.
14. Don’t use race oil on the street
We got this tip from Keith Jones at Total Seal. Using race oil on the street may not be a good idea. While the added zinc is good for flat tappet cam engines, the problem is a lack of detergents.
Race oils are designed to be changed often, so the detergent levels are drastically lower. Detergents are what clean the engine and actually work to reduce the effects of zinc. According to Jones, excessive zinc accumulates in the crosshatch pattern of the cylinder wall and can lead to excessive oil usage as the oil rings are overpowered.
If you suspect this as a problem, Jones says try using Shell Rotella diesel engine oil for a one-time use; it has very high detergents used to clean the soot from diesel engine combustion. The higher detergent level will clean out the zinc and reduce oil usage back to normal levels.
15. How to mount a trans cooler
With a typical automatic transmission cooler, there are several ways to mount the cooler. Our photo shows the best way, with the inlet and outlet fittings positioned at the top of the cooler. This way, any air bubbles that might be created will have a chance to be pushed out.
Another acceptable position is if we turn this cooler 90 degrees in either direction. The only position you don’t want is placing the fittings pointing downward. This will allow trapped air to remain in the cooler, reducing its efficiency.
This might seem a small thing, but it’s important if you want to obtain maximum efficiency from the cooler. Of course, this also means your trans will operate at a lower temperature, which is also a very good thing.
16. Let it bleed
When installing a new power steering box, it’s important to bleed the air out of the system before starting the engine. This prevents pumping air through the system that can take hours to stabilize.
Jack the car up so the front tires are off the ground. Fill the power steering pump reservoir with fluid and slowly turn the steering wheel to full lock in each direction. Air will exit through the reservoir as large bubbles, and you will likely need to refill it several times. When the large air bubbles no longer appear, most of the air is probably out of the system.
Start the engine and slowly turn the wheels a few more times. Check the fluid level, and you’re ready to go. If you don’t remove the air from the system before starting the engine, the extreme hydraulic pressure creates foam, which causes the pump to growl and will require long hours to eventually bleed out of the system.
17. 4L60E spotter’s trick
The 4L60E comes in two different cases. One is for the small-block Chevy in early vans and Chevy/GMC pickups up to approximately 2003. The more modern version is the LS version, which offers different case dimensions. The transmission cases come both one-piece and two-piece with detachable bellhousings. These different bellhousings will interchange between transmissions, but the converters do not because the input splines are different.
LS engines used a larger 300mm converter, so older trans will not accommodate the larger converter. The photo is for an LS-based 4L65E that is notable with the bolt hole at the very top. The small-block Chevy version does not have a bolt hole at the peak. Note also the LS version pattern is missing a bolt hole at the 10 o’clock position.
18. Let’s get vertical
Never mount round, oil-filled coils horizontally, as they can easily overheat. Oil is what keeps these coils cool, but they were designed to be mounted vertically. If this isn’t possible, convert to an E-core coil style. This design can be mounted in any orientation.
19. Copper gaskets
Sometimes, those copper brake hose sealing washers don’t seal like they should. Our long-time buddy, Bill Irwin, says he often hits them up with a propane torch to make them softer before bolting them in place allowing the soft metal to more easily seal to the caliper.
If the calipers are used, make sure the caliper sealing surface is flat and free of burrs. Also pay attention to offsets that are sometimes present in the hose on the caliper end. Make sure the offset doesn’t pinch part of the hose to the caliper.
20. Prime the pump – LS style
When starting a brand new late model LS engine, there’s no easy way to pressure lube the engine. GM recommends you remove the spark plugs and spin the engine over with the starter to get oil pressure up before starting the engine, but this doesn’t always work. That’s because the oil pump really needs to be primed first.
There’s an easy way that we learned from Melling to pre-fill the oil pump on LS engines. There’s a small oil pressure fitting toward the front of the driver side of all LS engines. Remove this plug and stick a length of 3/8-inch rubber fuel hose into this hole. Then, use a small funnel to pour a few ounces of engine oil into this passage. This leads directly to the oil pump and will pre-fill the pump. After replacing the plug, crank the engine; it should achieve oil pressure almost immediately.
The ATI Performance Products harmonic dampers have become extremely popular for engine builders and racers. They offer engine protection, and are available for many Mustang applications. There’s no argument that these dampers are made for high performance use, so naturally, Ivan’s 2015 Ford Mustang with Roush Performance TVS was our test mule.
So let’s get started with a few things to keep in mind:
The front bumper does not need to be remove to perform this install. We had the bumper off for other reasons. This job can be done with basic hand tools and a trusted 3 prong balancer puller and a long reach harmonic balancer installation tool.
Our car does have a Roush TVS supercharger on it, so a step or two will be different but we will cover that when the time comes.
REMOVAL
1. Make sure to grab two clean drain pans so you can reuse the coolant. Drain the engine coolant. As shown in the pictures above. On our supercharged model we had to also drain the supercharger intercooler system. The intercooler pump is located right by the windshield washer reservoir. We chose to pull the feed hose and let it drain into the pan.
2. Remove the engine coolant overflow tank. Two retainers are located on the top by the radiator cover. Two smaller hoses leading to the tank need to be removed also. One hose on the bottom and one on the top right.
3. Then, remove the supercharger intercooler tank. Two retainers are located on the top by the radiator cover. Two smaller hoses leading to the tank need to be removed also. One hose on the bottom and one on the top in front of the cap.
4. Remove the upper radiator hose.
5. Use a ratchet and socket to rotate the tensioner to remove the alternator and water pump drive belt.
6. Remove the three bolts on the water pump to remove the pulley. We did this for the added room and to make sure we have a clear view for the install.
7. On basic GT models you would next remove the AC belt.
** On our supercharged model we had to use a breaker bar and socket to rotate the tensioner to remove the belt.
8. Remove the two radiator fan mounting bolts. They can be found at the top right and top left sides of the fan shroud.
9. Remove the large grey wiring connector, for the fans, found on the passenger side of the shroud. Then the fan and shroud assembly will pull right up and out.
10. Using an electric or air impact remove the factory damper bolt. Make sure to remove the large washer behind the bolt.
11. Attach your 3 prong puller to the balancer and pull the balancer off. Be sure to go slow here and take your time.
BALANCER ASSEMBLY
For balancer assembly please follow the instructions included with your balancer provided by ATI Performance Products.
*The Super Damper shell assembly is indexed to the crank hub with an offset hole marked by an indent dimple on the front of the hub and on the front face decal with an arrow. These must be aligned for proper assembly.
INSTALLATION
1. Make sure both surfaces are crystal clean, one spec of dirt can gall the hub & crank snout up. Also be sure to remove the factory applied silicone off the keyway of the crankshaft.
2. Put anti-seize on the snout and an oil resistant silicone in the keyway slot of the new balancer.
3. Have your long reach harmonic balancer install tool ready.
Long reach harmonic balancer installation tool
Slide the new ATI Performance Products damper onto the crankshaft. Make sure to line up the keyway and not damage the crankshaft. It will only go on a little bit. Grab your installation tool and follow the tool instructions to pull the balancer onto the crankshaft. Make sure to follow the tool instructions carefully so the crankshaft is not damaged.
**Factory crank bolt is a one time, torque-to-yield, and must be replaced. We recommend replacing with a high-performance ARP bolt and using red loctite and torque to 120 lbs-ft.
FINAL ASSEMBLY
Install everything in the reverse order of removal. Once everything is back together make sure to refill the coolant and check for leaks.
An annular twist creates Edelbrock’s new AVS 2 carburetor
Words and Photos: Jeff Smith
There are very few new ideas in the world of carburetion. There are nuances and adept metering tricks that work in certain situations — but painfully few really new ideas. In the process of evolving performance, the sharp guys will huddle up and concoct a new way to apply an old idea.
For decades, Edelbrock has enjoyed a great reputation surrounding its Performer and Thunder series of highly-streetable carburetors. The rep is that you bolt on one, set the idle mixture and speed, and the carburetor performs flawlessly. But, the guys in the dyno room are always on the hunt for more power or better efficiency — or both.
Edelbrock’s Curt Hooker is one of those guys. He’s been the dyno operator and manager of the dyno cell and engine room for longer than he cares to admit. Last year, he applied a smidgen of that experience to adapt an annular discharge booster to the classic Edelbrock Thunder series carburetor. These carburetors employ an adjustable valve secondary (AVS) design, which uses a spring-loaded valve to control airflow through the otherwise mechanical secondary. Edelbrock calls this new carburetor the AVS 2.
The carburetor’s job is to introduce a proper mixture of fuel with the incoming air. A device used just about universally on all carburetors is a booster, placed directly above each venturi or throat. The booster is aptly named because it amplifies the velocity of the air travelling through the venturi.
By forcing a small amount of the total air to travel through the booster, the speed of the air increases, which (according to the Italian physicist Bernoulli) means the pressure inside the booster will drop. This low pressure essentially “pulls” fuel from the main jet circuit and introduces it into the carburetor. All carburetors use this principal to meter fuel.
The most commonly used booster introduces the fuel into the airstream through a single, large opening. The air travelling past the opening shears the fuel, producing small droplets that can more easily vaporize and eventually oxidize in the combustion chamber.
Annular boosters are different. Instead of introducing fuel through a single discharge hole, the annual booster uses a series of smaller holes that push fuel into the on-rushing airstream. The idea is that these smaller holes produce much smaller fuel droplets, which vaporize much more easily. In this way, it’s possible to improve power using less fuel.
Right away, you might question why all carburetors aren’t built this way. The main reason is that at high engine speeds and high airflow rates, the difference between a normal booster and an annular version becomes minimal. Another big reason is that annular boosters are usually larger, creating a restriction to airflow. But, if we’re talking about a street-driven car, where 90 percent of the driving occurs at lower engine speeds and throttle positions below 30 percent, this is where the annular booster really shines.
As we mentioned earlier, annular boosters are not a new idea. We’re not clear on exactly what carburetor first introduced an annular booster, but we know several production carburetors have employed these boosters with great success. Among the many examples was the 1985 Ford Mustang, the last year of carburetors for the 5.0L Mustang. Ford employed annular discharge boosters on the primary side of the carburetor in order to better control fuel at part throttle.
Since we were on a short timeline with this story, we wanted to do a quick conversion on our carbureted, small-block El Camino as a simple seat-of-the-pants comparison. We’ve spent some time with our current typical Holley 600 cfm carburetor and have been very pleased with the results, so this meant a quick swap to the new 650 cfm AVS 2 version with an electric choke.
Our El Camino is shifted by an electronically-controlled 4L60E, so it needed the addition of a throttle position sensor (TPS). We used a TCI adapter that uses a cable to drive a remotely-mounted TPS. This required using a cable mount, which we installed as an-under-carburetor plate with the cable mount attached. Except for this extra step, installing the new Edelbrock carb to replace our existing 600 cfm four-barrel was quick and easy, and they were both single fuel inlet carburetors. Once we reset the TPS range on our electronic trans controller, we were set to go.
With the engine warmed up, and with idle speed set, we adjusted the idle mixture screws to obtain our best idle quality. We were then ready for a test drive. In theory, the annular booster should offer a slight improvement in throttle response right off idle, and that’s exactly what the AVS 2 accomplished. Dropping the car into gear and a light step on the throttle produced an immediate improvement in throttle response.
We also noticed the AVS 2 required much less throttle opening to maintain a given speed. One of the specs displayed on our electronic transmission controller is throttle position as a percentage from idle (0 percent) to wide open (100 percent). According to the TPS report on our controller, the Edelbrock annular carburetor required 2 to 3 percent less throttle opening to produce the same rate of acceleration. That may not sound like much, but per our calibrated foot, it felt really good.
After spending 20 minutes driving in typical congested Los Angeles traffic, it was apparent the Edelbrock AVS 2 offered a significant improvement in throttle response. Even mashing the throttle from a dead stop produced what felt like quite a bit stronger low-rpm acceleration.
Once the engine revved past 4,000 rpm, there wasn’t a discernible difference, but the overall response certainly felt good. So, what we found is a noticeable improvement in light acceleration, especially right off idle. That might not seem something to get excited about, but for a mild street engine that spends 90 percent of its life at part throttle, this is a big deal.
Parts List
Description
PN
Source
Price
Edelbrock 650 cfm AVS 2, elec. choke
1906
Summit Racing
N.A.
Edelbrock 650 cfm AVS 2, man. choke
1905
Summit Racing
N.A.
Edelbrock 14” air cleaner, paper element
1221
Summit Racing
$29.95
Edelbrock universal GM cable adapter
8026
Summit Racing
$11.95
Edelbrock carb stud kit
8008
Summit Racing
$7.46
Of course, this is also based on the production jetting and power valve setting on our mild-cammed 383c.i. small block. While most enthusiasts will be happy with the stock calibration, we’re inveterate tinkerers, so we’ll play with metering rods and power valve springs to begin with, just to see if we can extract even more from our combination.
With an overdrive trans and lockup converter, setting it up to pull down perhaps 14:1 air/fuel ratio at cruise should not be difficult, and with annular boosters, the engine should respond positively to slightly leaner mixtures than is possible with single discharge boosters.
So, if you’re looking for input on choosing a mild street carburetor, the Edelbrock AVS 2 would be an outstanding choice. Edelbrock sent us an early production 650 carburetor, and the plans are at first to offer this 650 cfm electric choke along with a manual choke version. Future plans call for both 500 and 800 cfm versions.
Even with all this 21st Century talk about autonomous cars and how electronics are taking over modern life, there’s still room in the world for a well-designed carburetor.
This was done in a temperature controlled facility, so the install was the only thing that made a difference. Ivan also noted an immediate difference in the pedal, which is equally as important since this is a daily driven car — it’s no track queen! We will update the track times when the weather permits the tracks to reopen in the spring.
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