Just as the big-block GT500 from 1968 was a step up from the GT350, the 2008 Ford Shelby GT500’s 5.4-liter V-8 is a step up from the 4.6-liter V-8 used in Mustang GT – and even the landmark powertrain used in the last SVT Mustang Cobra. Not coincidentally, the new Shelby GT500 sports the largest-displacement engine installed in a volume version of the Mustang since 1973.
While the 5.4-liter V-8 block, dual overhead cams and four valves per cylinder contribute significantly to horsepower capability of the GT500, adding a supercharger and intercooler are the icing on the cake. In fact, the configuration is similar to the Ford GT supercar, offering the right combination of classic Ford big-block power and modern technology. Using the Ford GT as a blueprint, SVT engineers gave the GT500 more total horsepower than any factory Mustang in the car’s celebrated history: 500!
SUPERCHARGED PERFORMANCE
Using the stout, cast-iron, 5.4-liter Triton V-8 as a starting point, the Shelby GT500 employs a Roots-type 8.5-pounds-per-square-inch Eaton supercharger and water-to-air intercooler to help it produce a broad torque band on its way to making a satisfying 480 foot-pounds.
Adding forced-induction power is more than just a bolt-on proposition. A supercharged engine’s internals need upgrading for the sake of strength and durability. To that end, the Shelby GT500’s powerplant benefits from unique connecting rods and forged pistons to handle the extra strain on the lower end of the block.
The unique intake manifold helps to channel the supercharged fuel-air mixture into the cylinders. The special low-profile manifold design also effectively packages the entire induction system under the GT500’s functional air-extractor hood. Fuel comes from a dual-bore electronic throttle body borrowed from Ford’s 6.8-liter V-10 truck engine program.
FOUR-VALVE HEADS FROM FORD GT
While supercharging is a key element in the Shelby GT500’s ability to generate so much power, another major contributing component is the unique design of its cast-aluminum, four-valve cylinder heads, sourced from the Ford GT supercar. Machining changes have been incorporated into the outside ends of the heads and to the left-rear cam cap to fit the engine into the Mustang chassis.
Developed specifically for supercharged applications, these high-performance heads use high-flow ports and specially calibrated dual-overhead camshafts to deliver optimum engine “breathing” along with surprisingly good fuel efficiency and emissions.
GT500: POWERED BY SVT
To enthusiasts, the real beauty of any performance car rests with its engine. That idea certainly wasn’t lost on Carroll Shelby, because Mustangs that bore his name have traditionally brought his unique sense of style and personality directly into the engine compartment. One longstanding Shelby signature feature – special finned-valve covers embossed with “COBRA Powered By Ford” – soon became the envy of many Ford V-8 owners over the years.
The GT500 is equipped with special “Powered by SVT” finned-cam covers to hint at the beauty of all those horses lurking in the engine below. Mated to the Ford GT four-valve cylinder heads are unique exhaust manifolds that help to better scavenge spent gases out of the cylinders and into the custom-tuned mufflers and dual-exhaust system. To manage heat produced by those 500 horses, SVT engineers devised a set of GT500 specific features, including the air-extractor hood, a high-capacity aluminum radiator, an intercooler mounted below the blower, a loop-style power-steering cooler and an oil-to-water stacked-dish engine oil cooler.
SIX-SPEED GEARBOX
The gearbox used in the 2008 Shelby GT500 also is a rarity. Few transmissions exist in the marketplace today that can handle the torque loads generated by the supercharged GT500's V-8, so engineers have opted to stick with the proven heavy-duty performance of the TR6060 six-speed manual gearbox.
The GT500 employs an upgraded version of the T-56, which first appeared in the 2000 SVT Mustang Cobra R, powered by a naturally aspirated 5.4-liter V-8 with 385 horsepower, and later in the supercharged 2003 SVT Mustang "Terminator" Cobra whose DOHC 4.6-liter produced 390 horses. For the Shelby GT500, the six-speed manual is geared to make the most of the supercharged 5.4-liter’s broad power band.
Ford's “MOD” V-8 family of engines make more power than anything out of the factory in the past, yet tops 20 mpg on the highway and still meets the government's LEV-II tailpipe emissions standards.
SUREFOOTED PERFORMANCE
A major goal set for the Shelby GT500 was to take Mustang handling to the next level. Ford Special Vehicle Team chassis engineers worked to deliver a whole new set of standards worthy of the Shelby GT500 name.
The GT500 retains the same Mustang suspension setup that helped the Ford Racing FR500C win the 2005 Grand-Am Cup championship and claim the manufacturer’s title for Ford. The front features coil-over MacPherson struts with reverse “L” lower control arms made of lightweight I-section steel. In the rear, there’s a three-link live axle with coil springs, Panhard rod, outboard shocks and stabilizer bar.
Despite its bigger engine up front, the Shelby GT500 retains neutral handling thanks to the use of stiffer stabilizer bars. In addition, the rear bar is larger than that of the Mustang GT. The GT500 uses a 34-millimeter tubular front stabilizer bar. Coupe versions of the GT500 sport a 24-millimeter rear bar, while convertibles come with a 20-millimeter bar.
ALL THAT "GO" NEEDS EXTRA "WHOA"
A true performance car stops as well as it goes. To that end, the Shelby GT500 features Brembo front brakes with big, four-piston calipers and vented 14-inch discs. In the back, GT500 utilizes the Mustang GT’s 11.8-inch vented single-piston caliper rear-disc setup with unique pad material. Both Coupe and Convertible models ride on four 18-inch x 9.5-inch aluminum wheels, wearing 255/45ZR18 tires on the front and larger 285/40ZR18 tires on the rear.
To improve steering feel, the GT500 adds a brace that connects the rear lower arm bushings side to side. For added precision, a special steering pump is used, and the steering gear utilizes a unique torsion bar.
And just to make sure that all of the powertrain and suspension upgrades engineered into the GT500 meet enthusiast customer demands, SVT engineers not only proved-out their work at the test track, but also on real-world drive routes and race tracks. With that – and the approval of motorsports legend Carroll Shelby himself – they're certain that the 2008 Ford Shelby GT500 will live up to expectations.
SHELBY GT: POWERED BY FORD
Just like the GT500, every Shelby GT is built for real performance and is the result of extensive development. Unlike some specialty models, the beauty of the 2008 Shelby GT is more than skin deep. Under the hood, its Mustang GT 4.6-liter V-8 is upgraded with a Ford Racing Power Pack to increase output from 300 horsepower to 319 – with 330 foot-pounds of torque. The Power Pack includes a 90-millimeter cold-air intake and a new performance engine calibration for improved response.
A high-flow exhaust system with X-pipe crossover offers better power delivery and a throaty exhaust note. Plus, a shorter 3.55:1 rear-axle ratio is installed to capitalize on the Shelby GT’s extra power when accelerating off the line. The Shelby GT comes standard with a five-speed manual transmission featuring a Hurst short-throw shifter for precise shift action. A five-speed automatic transmission is optional.
Every Shelby GT sports fine-tuned driving dynamics with the addition of the Ford Racing Handling Pack, which was developed by the same engineers who developed the Ford Racing FR500C – winner of the 2005 Grand-Am Cup Championship. New coil springs drop the overall ride height by an inch-and-a-half for a more aggressive stance and a lower center of gravity. Stiffer dampers and front swaybar further enhance cornering feel and body control.
A Ford Racing front strut-tower brace adds additional strength to the Shelby GT chassis structure. All 2008s will wear 18-inch polished wheels with high-performance P235/50ZR-18 BFGoodrich g-Force tires to maximize the Ford Racing handling improvements.
Ford Racing has a full line of performance parts for Mustang enthusiasts to upgrade their vehicles. Whether in coupe or convertible form, the 2008 Shelby GT is yet another example of how, working together, Shelby and Ford Racing are developing, producing and delivering niche performance Mustangs directly to the customer.
GT500KR: KING OF POWER AND PRESTIGE
Ford, Shelby, Ford Racing and Ford SVT have all teamed up to turn the Shelby GT500 into the modern-day "King of the Road" with the limited-edition 2008 Shelby GT500KR. Its Ford SVT-engineered 5.4-liter supercharged V-8 has been treated to a Ford Racing Power Upgrade Pack that boosts horsepower to an estimated 540 and torque to 510 foot-pounds, thanks to revised ignition and throttle calibration and a cold-air intake system that replaces the stock unit. Calibration modifications include advancing the ignition timing as well as re-mapping of the electronic throttle settings to provide quicker throttle response for better off-line and mid-range acceleration.
The GT500KR's increased throttle response is met with a sharper roar from the Ford Racing-inspired exhaust system. Power is delivered to the rear wheels through a 3.73:1 rear axle ratio, upgraded from the GT500’s 3.31:1. Gear selection is courtesy of an all-new Ford Racing short-throw shifter making its debut on the KR. Topped with a white ball, the new shifter is 25-percent shorter than the unit on the GT500, providing for crisper, sharper shifts.
Ford SVT, Ford Racing and Team Shelby worked together to develop the KR’s suspension tuning. Based on initial work by Ford Racing and the team at Shelby (often at Shelby’s own facility on the grounds of Las Vegas Motor Speedway), the GT500KR will feature unique spring rates, dampers, stabilizer bars, and a strut-tower brace – all designed specifically for the KR by Ford SVT chassis engineers to best optimize the KR's engine enhancements.
Forty years ago, the 1968 Shelby Cobra GT500KR was a mid-year introduction, based on the 1968 Shelby GT500. Ford added "Cobra" to the Shelby’s moniker to help usher in the beginning of a new performance era at the company. The Cobra name heralded the new 428 Cobra Jet V-8 that was installed under the KR’s custom fiberglass hood. It was the high-performance engine that would once again vault the Mustang to the head of the pack.
Ford conservatively rated the 428CJ at 335 horsepower, but in reality it made more than 400 horsepower and some 440 foot-pounds of torque. The original KR model was also equipped with a modified suspension and was offered both in fastback and convertible versions. Ford dealers sold 1,570 GT500KR models in 1968 – 1053 fastbacks and 517 convertibles.
Just like its 1968 namesake, the 2008 Ford Shelby GT500KR builds on the strong foundation of the Shelby GT500. And once again, this time packing 40 more horses under its Shelby-inspired, dual-scooped hood, the all-new GT500KR reclaims its "King of the Road" status as the most powerful production Ford Mustang ever produced.