29. Chevrolet Corvette ZL1
The Corvette ZL1 was kind of a secret model but still it was one of the most unusual American sports cars. The heart of the ZL1 was the fantastic and basically racing-spec fully aluminum 427 V8 with up to 550 hp in mild tune. This monster of an engine was far more powerful than anything Mopar or Ford had in production at the moment. Chevrolet produced around 200 of those engines and while most of them went to Can-Am racing teams, Chevrolet also made around 12 test Corvettes with that engine inlate 1968. The performance potential was unbelievable and Chevrolet didn’t want to offer this wild racing engine to the general public, so the ZL-1 option was never mentioned in the press or official brochures.