Boost on Top: Vortech 351W

What better way to top off our top-end equipped 351 Windsor than with some Vortech boost?

By Richard Holdener

If you haven’t already checked out the two-part series we did on the junkyard 351 Windsor Ford, shame on you, because it was cool stuff. We pulled a 5.8L EFI motor from the engine bay of a full size F-150, slapped it right on the dyno, and were rewarded with roughly 250 hp. While that seems like a small number for a V8, especially one sporting over 350c.i., such was the state of affairs back in 1995 truck land.

Knowing there was more to be had, we replaced the stock heads, cam, and intake with a top-end kit (pt#2090) from Edelbrock. The kit included a healthy hydraulic roller cam (.573/.582 lift split, a 235/239-degree duration split and 112-degree lsa), a set of E-CNC 185 heads and Performer RPM Air Gap intake. Run in carbureted trim with a 750 Holley, the power output of the top-end equipped 351W jumped to more than 450 hp. This was reduced slightly (to 433 hp) in part 2 when we replaced the carburetion with an EFI RPM II upper and lower intake. After running EFI on the 351W, we started wondering what it might take to top our top-end kit?

Before the supercharger test, we upgraded the 351W with an Edelbrock top-end package that included a powerful cam and these CNC-ported 185 heads. We relied on Fel Pro 1011-2 head gaskets and ARP head studs to seal the system under boost.

The Edelbrock top-end kit originally included a carbureted RPM Air Gap manifold, but we installed this RPM II EFI intake.

The long-runner, two-piece RPM II EFI intake included this upper manifold. The upper intake was teamed with a 75-mm Accufab throttle body.

Fuel for the boost Windsor came from a set of Holley 83-pound injectors. Holley also supplied their Dominator EFI management system to dial in the air/fuel and timing under boost.

This MSD billet distributor was combined with a 6AL to help fire the fuel.

Installation of the Vortech supercharger kit began with the blower mounting bracket assembly.

In case you haven’t figured it out, the answer is boost. In fact, the answer to any performance question is always boost, and if a little boost is good, more must be even better, right? To illustrate just how good boost is, we decided to top the 351W with an efficient Vortech supercharger.

Given the impressive maximum specs of 1,150 cfm, 22 psi and 750 hp (a conservative rating by Vortech by the way), it is not surprising we chose the Vortech V3 SI trim for our Windsor. We had no intention of reaching, let alone surpassing the maximum power level listed by Vortech, but we liked the fact the SI V3 offered such a high adiabatic efficiency rating (translation: lower charge temps under boost).

The supplied 6.0-inch blower pulley fit directly inside the factory lower crank pulley on the 351W (or 5.0L). The kit included the necessary bolts to secure the pulley combination to the factory damper.

With the mounting bracket in place, we then installed the V3 supercharger. The V3 featured self-contained oiling, eliminating the need to punch a hole in the oil pan.

Thanks to a peak efficiency of 78 percent and maximum impeller speed of 52,000 rpm, the V3 SI-trim used for this test was capable of supporting more than 750 hp (1,150 cfm) at 22 psi.

We chose to start the test with the largest blower pulley in our kit. The 3.625-inch pulley produced a peak boost reading of 5.9 psi.

The kit included this fixed-load tensioner to minimize belt slippage. We relied on a six-rib system, but at the elevated power levels offered by the Vortech, it might be a good idea to step up to an eight-rib system.

All testing was run through a set of 1 ¾-inch, Hooker long-tube headers.

Before adding boost, we dialed in the 351W in normally aspirated trim to establish a baseline. Equipped with the Edelbrock top-end package, the 351W produced 433 hp at 5,700 rpm and 430 lb-ft at 4,900 rpm.

Though we planned on keeping boost to a minimum on our non-intercooled combination, we did want to maximize the power output at those lower boost levels. We also liked the fact the V3 featured self-contained oiling, thus eliminating the need to supply oil to the blower or punch a hole in the pan. Yes, the Vortech V3 offered an impressive combination of power potential, reliability, and ease of installation.

We installed the Vortech V3 onto the awaiting Windsor using a 3.625-inch blower pulley. This was teamed with the supplied 6-inch crank pulley, which produced a maximum boost pressure of 5.9 psi at our peak engine speed of 6,000 rpm. Quick math told us that using the 3.625-inch blower pulley and 6-inch crank pulley combined to produce a drive ratio 1.655:1 (6.0/3.625).

When we factored in (multiplied) the internal step ratio (gearing inside the blower) of 3.6:1 and a maximum engine speed of 6,000 rpm, we got a maximum impeller speed of 35,751 rpm. This was obviously well under the maximum of 52,000 rpm listed by Vortech, so we knew there is much more power to be had from the V3. We purposely started out on the safe (low-boost) side of the equation. Equipped with the Vortech producing just under 6 psi, the supercharged 351W produced 559 hp at 6,000 rpm and 518 lb-ft of torque at 4,800 rpm. Running under 6 psi, the Vortech improved the power output of the 5.8L Ford by more than 125 hp!

All we had to do to get the blower pumping out boost was to install the serpentine belt and tighten the tensioner.

The final step was to install the discharge tube connecting the Vortech supercharger to the Accufab throttle body.

After tuning with the Holley EFI system, the supercharged 351 produced 559 hp and 518 lb-ft of torque at a hair under 6 psi.

The great thing about the Vortech supercharger was the ability to easily adjust the power output by swapping blower pulleys. We replaced the 3.625-inch pulley with a smaller 3-inch pulley with amazing results.

As impressed as we were with the results of the supercharged combination, we couldn’t help but smile knowing there was much more to be had, and how easy it was to unleash it.

The great thing about supercharging is more power is never more than a pulley swap away. Do you want more power? Just add more boost. Of course, there is a limit to the fun, but we were nowhere near that limit on our low-boost Windsor. So, we swapped out the 6.25-inch blower pulley for a smaller 3-inch pulley. This increased the impeller speed to 43,200 rpm, a jump of almost 7,500 rpm. This increase in blower speed pushed the peak boost pressure up to 10.5 psi and the power right along with it. Run at 10.5 psi, the Vortech 351W produced 645 hp at 6,100 rpm and 584 lb-ft at 5,100 rpm.

It bears mentioning that you should consider intercooling at this elevated boost level, and Vortech offers systems designed to help lower the charge temps (especially important on pump gas).

We loved how the Edelbrock top-end kit increased the power output of the 351W by more than 180 hp, then loved it even more when the Vortech topped the top-end kit by 213 hp. The question now is, how do we top this?

Modified 351W Ford-NA vs Vortech V3 (6 & 10.5 psi)

The stock 5.8L EFI Ford (351 Windsor) was upgraded with an Edelbrock top-end kit that included a healthy hydraulic roller cam, E-CNC 185 heads, and the RPM II EFI intake. Run in normally aspirated trim, the modified 351 produced 433 hp and 430 lb-ft of torque. After topping the top-end kit with a Vortech V3 supercharger, the power output jumped to 559 hp and 518 lb-ft of torque at a peak of 5.9 psi. As much as we liked adding more than 125 hp to our 351W, we knew there was more to be had. Stepping down from a 3.625-inch to a 3.0-inch blower pulley increased both boost and power. Running a maximum of 10.5 psi resulted in 645 hp and 584 lb-ft of torque.

Equipped with the smaller blower pulley, the Vortech-supercharger 351W produced 645 hp and 584 lb-ft of torque at 10.5 psi. I guess topping a top-end kit with boost really works!

Sources: Accufab;accufabracing.com, Edelbrock;edelbrock.com, Holley/Hooker;holley.com, Lucas Oil;lucasoil.com, MSD;msdignition.com, Vortech Superchargers;vortechsuperchargers.com