340 with edelbrock heads overheating

lilcuda said
Aluminum heads are more resistant to detonation than iron and therefore they can typically be run at higher compression than iron. I don’t know how good the gas is where the OP is, but I’ll bet the increased compression is not the issue.

I believe RAMM or another engine builder here did a dyno comparison. And the aluminum resistance was in tenths. Not a whole number.

If he was 10:1 before and now it's 11:0, the detonation resistance will not cover that on 91 octane pump gas typically with that cam.

It all depends where the x-heads were at. If before was under 9.0:1, he may be ok.

And the number he's at right now may be ok in theory. But the compression jump may be bringing to light other issues.