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  2007 Shelby GT500 - PowerTrain

  Apr 3, 2005
  By:  Ford Media

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. Also borrowed for use in the GT500 are the Ford GT's proven piston rings and connecting rod bearings.

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 right into the engine compartment. One Shelby signature feature special finned valve covers embossed with "COBRA Powered By Ford" soon became the envy of so many Ford V-8 owners that they quickly became one of the best-selling dress-up accessories on the market.

With that in mind, the GT500 is equipped with special "Powered by SVT" finned cam covers to hint at the beauty of 450 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.

Strong transmission for powerful engine

Few transmissions exist in the marketplace today that can handle the torque loads generated by the supercharged GT500, so SVT engineers are opting to stick with the proven heavy duty performance of the T-56 six-speed manual gearbox. The T-56 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 Cobra whose DOHC 4.6-liter produced 390 horses. For the Shelby Cobra GT500 show car, the T-56 will be geared to make the most out of the supercharged 5.4-liter's broad power band.

Mustang then and now - twice as powerful, only a small percentage of the emissions

The Ford Shelby Cobra GT500 show car provides a powerful choice in an efficient and clean package, especially considering muscle cars of the past. "When you consider pony cars of the 1960s, today's engines produce approximately double the power, four times the fuel economy and 100 times fewer emissions," says Tom Jones, Ford SVT program engineer.

Performance cars have evolved dramatically since their heyday in the 1960s. In terms of safety, efficiency and refinement, today's street machines totally outperform their elder muscle car colleagues in nearly all categories. Yet the story is seldom told about the tremendous gains made in reducing emissions while increasing overall power output. The fact is the GT500 is easily twice as powerful as the hottest V-8 package offered when Mustang was first introduced yet still produces from 100 to 300 times fewer emissions. Additionally, today's modern "MOD" V-8 powertrain enjoys a nearly 60-percent increase in average fuel economy compared to corresponding Ford products produced 30 years ago.

Back in the so-called Muscle Car era, driving a street beast with more than 400 horsepower was a dicey proposition. When dual carburetors, progressive linkage and dual-point ignitions were part of the equation, performance came with a price drivability. Running too lean or too rich or with the timing or spark out of adjustment could mean it would misfire or "carbon up" sometimes with thick, black smoke coming from the tailpipe. Worse yet was fuel economy, with most of the big, high-powered V-8s at the time netting anywhere from six to 10 miles per gallon (mpg) in typical driving.

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 meets the government's LEV-II tailpipe emissions standards.

Multi-valve engine technology improves both power and efficiency

Cast "Powered by SVT" coil covers finish the four-valve heads sourced from Ford GT.
Modern, race-derived technology provides an interesting power comparison: The GT500 with a 5.4-liter, DOHC, supercharged V-8 produces nearly 100 horsepower more with nearly 100 fewer cubic inches versus the 1967 Shelby GT500's 355-horsepower, 428-cubic-inch-displacement, big-block V-8.

Creating a powerful engine means designing it to be as efficient as possible, making the most of the fuel and air that makes it run. The benefits are not only seen in overall power, but in reduced emissions and improved fuel economy as well.

"People may not realize that typical hot-rodding techniques involve improving an engine's efficiency to extract more power from every ounce of fuel that is burned," notes Jay O'Connell, SVT chief vehicle engineer. "It's an unexpected benefit automakers get from racing the tricks to winning on the racetrack can help make cleaner, more fuel-efficient vehicles for the street."

For example, the GT500 uses four-valve, double-overhead-cam cylinder heads for optimum engine "breathing." Using multiple valves per cylinder provides the engine with a more efficient airflow, generating higher peak horsepower. As an additional benefit, multi-valve engines better utilize the air-and-fuel mixture in the cylinders with less waste and unburned fuel vapor. Also, multi-valve engines are better suited to help scavenge exhaust gases out of the cylinder after combustion is complete for more power with cleaner tailpipe emissions.

In addition, supercharging produces the peak horsepower of a much larger-displacement, naturally aspirated engine. Yet, at lower throttle applications, the smaller displacement enabled by supercharging consumes less fuel, resulting in increased fuel economy and lower emissions. As a result, the Shelby Cobra GT500 show car is designed not only to be the most powerful Mustang from the factory but also one of the cleanest. The return of Carroll Shelby to our performance family only strengthens our firepower.


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