Richard Holdener
September 14, 2007
While the 5.4L Ford GT motor comes factory equipped with a twin-screw supercharger, replacing the smaller 2.3L blower with a massive 2.8L unit from Kenne Bell adds some serious muscle.

Let's face it, if we at MM&FF have something worthwhile to test, or even something less than worthwhile-heck, if we have anything at all to test, you'll find us strapping down an engine and pulling the lever. There's nothing more satisfying than running a motor on the dyno, making changes, and discovering the power gains (or losses) associated with the changes. We live and breathe for dyno graphs, so when the guys at Accufab invited us for another wild dyno session, naturally we were in.

When they said they were running nothing less than a 5.4 Ford GT bullet, we were doubly in. While we've run a number of tests on the chassis dyno with Ford's supercar, we'd yet to see one strapped to the engine dyno. There were, after all, a great many hurdles to overcome just to get the motor running, never mind the performance upgrades.

The dry sump, dedicated blower drive (with attending accessories) and lack of a conventional (mod motor) starter made installing the GT mill much more difficult than your garden-variety Cobra motor. There was plenty of fabrication involved just to get it running, but with a name like Accufab, making pristine pieces from ordinary chunks of steel and aluminum is second nature.

With success a certainty (though a time-consuming one), the boys at Accufab decided to do more than just run the stock GT motor. Sure, it was interesting just to compare the rated power output to the actual power in our configuration, but MM&FF readers deserve so much more. With power gains just a pulley swap away, why not take the opportunity to run a few tests to produce those magnificent power curves?

Let's face it, the Mustang has been and will always be the most popular and successful ponycar. But what Ford needed (and now needs again thanks to the recent demise of the GT) is a car capable of taking it to the gold-chain Corvette crowd. Even GM's mighty 505hp Z06 is no match for the GT. While not quite matching the 7.0L displacement of the original GT40s, the 5.4L modular motor offered an efficient, positive-displacement supercharger pushing 11 psi of boost. The 74 percent hike in pressure increased the "effective displacement" of our 330-inch motor to something more like 575 inches.

The highlight of the 5.4L Four-Valve modular motor used on the now-defunct Ford GT was the 2.3L twin-screw supercharger. Perhaps the best part of owning a supercharged motor is the ability to crank up the boost.

Rated at 550 hp, every test run on a Ford GT has shown that, much like the '03-'04 Cobras, the power numbers seem somewhat conservative. Running the stock motor on the engine dyno would give us a chance to verify the numbers offered by Ford. It would also give us a chance to step things up, since the best thing about owning a motor with factory forced induction is the ability to crank it up. While there's a limit to the power gains available from any blower, the gains offered with additional boost are far greater than the usual array of bolt-ons applied to a normally aspirated combination.

Using a new HDC drive system offered by Kenne Bell, we were able to crank up the boost on the factory supercharger before eventually replacing the stock 2.3L blower with a much larger (and efficient) 2.8L blower (also from Kenne Bell). At the risk of spoiling the results (as if you guys haven't already memorized the power curves), the larger blower allowed us to easily exceed 800 hp. To put this into proper perspective, a good Holman & Moody 427 side-oiler race motor probably put out something near 550 hp (having never officially dyno'd one, we can't say if that was a net or gross rating). In any case, this new GT motor has the ability to far surpass its predecessor in terms of power out.