All the heavy duty parts were kept but the compression went to 9.2:1. In 1972 the Cobra Jet motor was renamed HO for high output. The compression was 9.0:1 in both motors. The motor was the same as the stock 4 barrel 351 Cleveland.

Same Cast iron intake as the 4 barrel Clevelandīy 1972 the Boss motors were gone. Spread bore Autolite carb with smaller primaries and larger secondaries Hydraulic cam slightly hotter than the stock 4 barrel motor with a little longer durationĭifferent heads - large ports & valves of the 4 barrel with the open design of the 2 barrel versionĩ.0:1 compression (Compared to the 10.7:1 in the 4 barrel motor) It featured: First offered in 1970, the 351 Cleveland motor came as a 2V and a 4V engine. The mid '71 Boss 351 (Cobra Jet) engine wasn't much of step up from the stock 4 barrel motor. New air quality standards put better smog controls on the motors, affecting the performance. High octane gasoline was getting harder to find. Insurance rates were going up on cars with these motors. It was during these years that the performance engines were under a lot of pressure. In mid May of 1971 Ford introduced a new version of the 351 Cleveland motor. The 1971 Boss 351 could be called Ford's greatest performance small block motor. The Boss motor option was called the Boss 351. The heads on the 351 4 barrel engine were very similar to the Boss 302 heads.In 1971, Ford offered only a two barrel version of the 302 motor. Even though the Cleveland 351 came from the small block family, few parts will interchange. The Cleveland 351 is between a small block and a big block. The Windsor motor is considered a small block. Ford offered two versions of the 351 engine, a Windsor 351 and a Cleveland 351.

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