What specifically is "neutered" on 1970s-1990s era engines?

[Chris142]

The 1970,4bbl 350 Chevy had a 10.25-1 compression ratio. The 1971 had 8.5-1 compression with the only change being the heads. 64cc vs 76 cc.

Starting about 1975 they redesigned the ports in the heads and that's when power really took a hit.

The 71 engine still had heads that flowed well for the time and a good tuner could still get some power out of one .

 

[HouseTiger]

My 1975 Buick Century had a 350 with 4bl Rochester. The cat converter was removed, and some other work done by an aquaintence that lived to soup up cars . . . result, it would pass almost anything on the road except a petrol station.