. . . forced manufacturers to lower compression ratios. There were still a few high-performance engines offered in '71 and '72 but by '73 they were all gone except for Pontiac's 455 HO. The very last high-performance engine was the '74 Pontiac 455 HO . . . unfortunately only a few were made. It wouldn't be 'til twelve years later that performance returned to the American motor scene.