Just before the season opener of the American Le Mans Series (ALMS) at the Sebring International Raceway in Florida this past weekend, GM aired an aggressive commercial touting its 638-horsepower-strong Corvette ZR1. The ad claims that the firm’s engineers had to reduce the stock ZR1’s LS9 engine output by 168HP in order to compete in the race and “just to be fair against Porsche, Ferrari and BMW”.

For one, the Corvette ALMS racers are actually powered by a V8 loosely based on the Z06’s LS7 engine (see the second video after the jump). Perhaps most importantly, the Corvettes finished third and fourth in the GT class in Sebring behind two BMW M3 GTs… Videos follow after the break.

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