When it was introduced at the North American International Auto Show in Detroit earlier this year, the 2009 Corvette ZR1’s power was estimated at 100 horsepower for each of its 6.2 litres of displacement. Now comes news that GM Powertrain has completed SAE certification of the ZR1’s supercharged LS9 V8 and the results exceed the estimate: 647 horsepower and 604 lb-ft of torque.

The supercharged LS9’s output is nearly 103 horses per litre, or just about 1.7 horses for each of the engine’s 376 cubic inches. It is unquestionably the most powerful automotive production engine ever manufactured by General Motors and enables the Corvette ZR1 to achieve a top speed of 330 km/h.

“One of the most amazing things about the Corvette ZR1 is the level of refinement that our designers and engineers have attained. Even with all that power, this car has road manners that will allow our customers to enjoy it on the streets as a daily driver, and on the track,” said Chevrolet’s U.S. GM Ed Peper.