Ford GT Motor Modifications - Mods For Ford GT Mods

Things are good for your author, since I was recently lucky enough to be invited to a standing-mile acceleration test put on by our sister magazine, Motor Trend. That ranks high on the cool scale, especially given my affinity for all things related to top speed. Leave the drag racing to Smitty and Galimi-I prefer road racing, and even trips to Bonneville and El Mirage. This standing-mile acceleration test slots in there nicely, too.

As if the top-speed event wasn't enough, I also had a kind Ford GT owner use his car for the test. Imagine, a Ford GT owner willing to let us crank up the boost and timing, and fiddle with all the intricate items in the motor in order to make what is arguably the fastest vehicle ever to come with a Blue Oval even faster. Heck, the stock GT has been clocked at over 210 mph (sans limiter).

Preparation for the event allowed yours truly to gather much needed data for MM&FF's ongoing "Mods for Mods" series. Obviously, no such series would be complete without information on the ultimate modular motor, the Ford GT version.

The 5.4L Four-Valve combination stuffed into the rear (actually middle) of the low-slung Ford GT supercar combines all the torque-enhancing displacement of the supercharged Two-Valve Lightning motor with the free-breathing four-valve heads of the '03-'04 Cobra. In fact, this Ford GT motor does those systems one better by selecting not just any old supercharger, cylinder heads, short-block or oiling system. The 5.4 block used in the GT is specific to that application and features aluminum construction and dry-sump oiling. This means the block cannot be retrofitted for use in a Mustang chassis without taking the machining steps necessary to provide for the starter and wet-sump oiling system.

While the 5.4 Lightning and '03-'04 Cobra motors made do with the Eaton roots super-charger, the Ford GT is boosted by a 2.3L twin-screw supercharger. Considerably more efficient than the Eaton Roots blower used on the Lightning and Cobra applications, the twin-screw design provides the flow potential (and efficiency levels) required for supercar power levels at a reasonable boost pressure. Gains of 50-100 hp are available with just a pulley swap. Making that pulley swap happen is a bit more complex than yanking off the old one and installing a new one, but Kenne Bell has seen to make that exact scenario a reality for the handful of lucky GT owners.

We mentioned previously that the 5.4 is blessed with four-valve heads to maximize the breathing potential. While the '03-'04 Cobra heads would certainly offer flow and power gains over the two-valve PI heads used on the Lightning, the Ford GT engineers reached all the way up to the top shelf for headgear for their supercar.

Far and away the best set of factory cylinder heads for the modular motor came on the '00 Cobra R. The R heads featured revised port locations that offered tremendous gains over the standard offerings. Nestled between the impressive cylinder heads and 2.3L twin-screw supercharger was a dedicated intake casting and improved air-to-water intercooler. Rather than rely on the effective air-to-water intercooler system on the '03-'04 Cobra motor, the GT engineers stepped up things once again and designed a larger, more efficient intercooler system for the 5.4. Like the Lightning and Cobra intercoolers, the system used on the GT will easily support (and effectively cool) elevated boost levels.

Extensive cooling studies and powertrain development went into the GT project, the results of which were a motor capable of supporting a great deal more power than the rated output of 550 hp. We are proud to say that, like the '03-'04 Cobra before it, the power output of the Ford GT is significantly underrated. We measured near 550 hp (and 500 lb-ft of torque) at the wheels in bone-stock condition. No wonder this car will kick the living crap out of a Corvette.

Technical details abound for the Ford GT, but this episode of "Mods for Ford GT Mods" covers the ease at which we improved the power output of the already powerful supercharged 5.4L motor. Obviously, the first thing we needed to do was establish a baseline. Since the testing was performed at Kenne Bell, we hooked up all manner of data-logging equipment in order to take an in-depth look at the important variables that affect the generation of the power curve. Naturally, the torque, horsepower, and air/fuel curves are provided by the Dynojet, but for our needs, we also took a look at the timing curve, air temps (in and out of the blower), and even injector pulse width. Basically, we had all the data necessary to determine not just that we improved the power output, but (every bit as important) why a specific power gain occurred. The data would also be helpful in sourcing potential problems, but as luck would have it, none developed during testing.

Running the car in as-delivered condition, the impressive supercharged Four-Valve pumped out 562 hp and 503 lb-ft of torque at a maximum boost pressure of 11.7 psi. The wavy curve made it difficult to pinpoint the exact power peak, but know that this motor is rated at 550 flywheel horsepower and manages at least that much at the wheels in stock trim. As we have come to expect of these supercharged mod motors, the twin-screw-enhanced 5.4 offered a broad, flat torque curve. The motor exceeded 440 lb-ft of torque at the wheels as low as 2,000 rpm and hovered near 500 lb-ft for a solid 1,000 rpm. Even out at the factory rev limiter of 6,600 rpm, the torque curve was still showing 445 lb-ft. From the looks of the curve, we suspected the power curve was still on the rise as the engine encountered the 6,600-rpm rev limiter. Since the guys at Kenne Bell were set up with SCT software, we had the ability to raise the factory rev limiter. This modification would come after we increased the boost pressure via a brand-new billet blower-drive assembly from Kenne Bell. Since both the air/fuel and timing curves were conservative from the factory, we felt confident in cranking up the boost a few pounds.