MN71W30

Is there a piston dish difference between 1971 455 and a 1974? I remember reading once that the compression was changed by opening the head chambers after 73 so they used a less dished piston. I was thinking that I could throw on a set of 80cc E heads and end up with a better compression ratio than 8.0. Any truth to this?
Thanks for any advice.

citcapp

Lots of good information in the "tech" forum in the heading at the top of the page

In general terms the engines before 1971 had the higher compression with small dish pistons. Later versions had deeper dishes dropping the compression to around (8.0 to 8.5) Most of the heads have 80cc with a few exceptions D heads were smaller but these heads are rare and command high prices 2k+ or you can go to Edelbrock allumimun heads 77cc.

Best buy is aftermarket pistons and C big valve heads for better flow

Just my opinion

joe_padavano

With the exception of the 1968-69 "D" heads, all BBO heads have the same 80-ish CC chambers. The size of the dish was what determined the CR. Different dish sizes were used from 1968 through 1976.