ive been lookin around for some pistons for my 390, cause it got the nasty truck pistons. id like to produce somewhere in the mid 10s. i found some hypreutectics that made 10:1 but still would like to see if i could find some 10.5:1s or a little more. its got a isky cam with 270/270 .543 106deg lobe center. what would be the max comp. i could run with this cam at 91 octane? i know this varies between engines, my friend runs his 460 with 11:1 on regular. of course alot of headwork went into doing that.
With that cam you can run 9.1 and be fine. 10 to 1 would be to much for pump gas and a heavy car. The 270 is total or .050?
Alot will depend on the amount of valve overlap, and the amount of spark advance. How well does the FE tolerates 91 in a stock setup? Compare your cam overlap to the stock specs; no doubt you have more and this will bleed off some pressure. .
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