450 hp L72 rating

[Stefano]

The 427 L72 was released in the 1966 Model Corvette and rated by the factory at 450hp in the early car and 425hp in the later cars. Same engine different rating. The L78 /396 was also rated at 425hp for the '65 Corvette.

While I certainly can't speak for the man, I would speculate that Don Yenko who was very familiar with the Corvette Engine used GM's own marketing specs. and Dyno Results to rate his Super Cars.

It was after all the same L72 over the counter blocks which Yenko Sports Cars Inc. began installing between the fenderwells of their first Camaro Super Cars.

Just My opinion and observations.