Carroll Shelby started working on Fords again in 2005 after almost 40 years of absence. The first Shelby Mustangs recalled classics like the Hertz Rent-A-Racer, but these cars just added a few performance parts to the standard Mustang. That changed with the introduction of the GT500 in 2007, a full-blown performance car recalling the G.T. 500 of the late '60s.
While the original G.T. 500 used a giant motor to add power, this new model uses a combination of displacement and forced induction. Shelby worked with Ford's Special Vehicle Team (SVT) to fit the Mustang with a twin cam supercharged 5.4-liter engine. It's easy to mistake this motor for the one used in the GT supercar, but there are a number of differences: instead of the GT's Lysholm screw-type supercharger, the designers chose to go with an Eaton R122 Roots-type blower. This choice was made primarily because Lysholm couldn't produce enough parts to meet the car's expected 10,000 units per year production rate, but the Eaton also offers better mid-range performance making it a better match for a pony car. The GT500 also uses an iron block in place of the GT's aluminum unit to save costs.
This engine was rumored to produce 450 HP before release, but the production engines were able to handle 13.5 PSI of boost, 3.5 more than originally planned, bringing output up to 500 HP.
This big engine weighs 350 lbs. more than the 4.6-liter V8 used in the standard Mustang GT. To compensate, the front suspension has stiffer springs and shocks coupled with a larger stabilizer bar, and the rear axle uses stiffer springs and a Panhard bar to help handle the extra power. While the motors may be different, the GT and Shelby share the same Brembo brakes with four-piston calipers and 14-inch vented rotors up front coupled with twin piston calipers gripping 11.8-inch vented discs at the rear. Massive 18 x 9.5-inch wheels, specified by Shelby himself, help keep the car glued to the ground. All those modifications don't just aid the car's track prowess; they completely disguise the car's front-heavy weight distribution. Coupled with the car's Tremec TR-6060 6-speed manual, these modifications push the GT500 beyond muscle to create an effective track car.
