twilightblue28A

Is there a difference between the heads on a 442 455 engine 1970 vs 1971? Thanks

tru-blue 442

E vs. G. No real diff though.

twilightblue28A

Are the intake and exhaust valves the same size on the 1970 442 455 E heads compared to the 1971 442 455 G heads. Why is the compression 10.5:1 on the 1970 and lower on the 1971 442 455? What is the compression on the 1971 455 442?

twilightblue28A

Also exterior paint code 28 on 1971 442. Can someone describe the blue color? Is 26 Viking blue or between Viking and twilightblue

vette442

Twilight blue is darker (more Navy blue) than Viking Blue.

Fun71

Olds dropped the compression ratio from 1970 to 1971 by using pistons with larger dishes in them, while keeping the head combustion chamber volume the same. '71-up 350 and 455 engines were rated 8.5:1 compression ratio.I think this was due to the introduction of unleaded lower octane fuel and stricter emissions standards.

joe_padavano

Actually, this was due to the federal mandate to use low-lead fuel for the 1971 model year. Unleaded didn't come into mainstream use until catalytic converters were mandated for the 1975 model year. Along with the lower compression, all 1971 Olds heads have induction hardened valve seats to accommodate the low-lead fuel. This is the fundamental difference between the 1970 and 71 heads. The induction hardened seat is a local treatment of the cast iron, not a separate press-in seat.

Note that not all E or G heads got big valves. In 1971, only 442s, Toros, marine, and irrigation engines got big valves. Other G-head engines got small valves.

Fun71

Ah yes, low lead preceded no lead by a few years.