" From: Jim Blair <carnuck@xxxxxxxxxxx> " " " I've had 4.2L heads posted for sale for some time and no-one has been " interested. ($50 with the '80 tin cover) The combustion chamber was " made bigger on the later models, which will affect compression ratio. " I found that out when I put an early 72 head on my late '70s model " engine. Ran like a rocket but burnt oil like crazy until the pistons " collapsed. '64-7 head was 56cc; '68-'76 was 66cc; '77-80 was 74cc. i've never seen specs for the '80s but c.r. bumped from 8.0:1 to 8.3:1 to 8.6:1 to i think 9.2:1, and the only change i can track was head p.n. pistons also changed along with the heads '60s-'70s. late '70s slugs have less dish than early '70s, but again i don't know specs. ________________________________________________________________________ Andrew Hay the genius nature internet rambler is to see what all have seen adh@xxxxxxxxxxxxxxxxx and think what none thought _______________________________________________ AMC-list mailing list AMC-list@xxxxxxxxxxxxxxxxx http://list.amc-list.com/listinfo.cgi/amc-list-amc-list.com