• Ford Shelby GT500 officially rated at 500 horsepower, 25 horsepower higher than preliminary estimates
• The Shelby GT500 will go on sale in North America this northern summer with more horsepower than any previous factory-built Mustang

The most powerful factory-built Mustang ever just got even more potent. Final certification testing of the Shelby GT500’s 5.4-litre supercharged V-8 shows it will produce 500 horsepower and 480 lb.-ft. of torque – 25 more horsepower than preliminary estimates.

“With 500 hp and the Shelby name, this car is an instant legend," said Hau Thai-Tang, director, Advanced Product Creation & SVT programmes. "This is the most powerful, most capable Mustang ever."

The Ford Shelby GT500's supercharged 5.4-litre, 32-valve V-8 is a result of Ford's experience in developing the modular V-8 and V-10 engine series. The engine is force-fed air via a "Roots-type" supercharger providing 9 pounds per square inch of boost. It borrows the four-valve cylinder heads, piston rings and bearings, from the Ford GT engine.

The 500 hp rating was obtained using the Society of Automotive Engineer's latest standard and was witnessed by an objective third party. The Shelby GT500's 5.4-litre supercharged V-8 will be built at Ford's Romeo Engine Plant in Romeo, Michigan (USA).