Thanks Gents - but I am still not clear on the specific difference(s) between the 70 350HP rated motor vs 71 375HP rated motor. I see there was a compression drop in '71 based on BODY67's response. One would think the 70 with high compression would make more HP. So this seems counterintuitive to me. Were the heads the same between the two years? If so, then I assume the piston was changed to drop the compression in '71? Were the cams the same? Not trying to nitpic, just trying to understand the mechanical differences between the engine's HP rating. How about the carb? were they the same between the two? Maybe better free flowing exhaust manifolds? Things like that are what I was trying to pin down. Thanks again for all your help.
Mark
As was the case in other years, in 1970 and 1971 both a base 440 engine and a high-performance version of the 440 was offered. The high-performance version went by the name of "Super Commando" with Plymouth, "Magnum" with Dodge and "TNT" with Chrysler.
Stricter tailpipe emissions regulations called for a lowered compression in some engines, among other things, for 1971, resulting in a slight drop of power over the previous year.
Beginning in 1971, manufacturers also had to state the then new net horsepower (net hp) figures versus the previous brake horsepower (bhp) which were due to a different test setup and resulted in significantly lower numbers.
The horsepower ratings were:
1970 standard 440: 350 bhp
1971 standard 440: 335 bhp (220 net hp)
1970 high-performance 440: 375 bhp
1971 high-perofrmance 440: 370 bhp (305 net hp)
In both years, the high-performance version of the 440 eninge sported low restriction exhaust manifolds, larger diameter valves and a special camshaft (among other items) to set it apart from teh base 440 engine. The 1970 high-performance 440 featured the same 9.7 to 1 compression ratio as the base 440 engine. The 1971 high-performance 440 engine had a 9.5 to 1 compression ratio while the 1971 base 440 engine's compression ratio had been lowered to 8.8 to 1.
The 1970 440 six pack engine had an even higher compression ratio of 10.5 to 1. The six pack was not offered in a C-body in 1971 anymore.