340 cam for 318

Baggs said

Well, I used Wallace racing, with .080 down and a .032 compressed gasket, using 68cc, 8.24:1
I used 64cc heads, 8.51:1.
So I suspect the closed chambered heads must be 62 cc, and that may be where the 8.6:1 number was for?
.080 below deck at TDC holds with my engine, it’s .030 over, and .095-.105 below deck, I attribute the difference to common rebuild pistons that have .020 lower compression height.
I’m unsure what a normal CH head gasket was on a 318 new, I’d think .039?, but .032 was the smallest I could find except for a marine HG at .015.

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Yes, standard aftermarket pistons, seem to go to the lowest compression. The factory pistons were "adjusted" for any changes. Original head gaskets were somewhere between .020 and .040. I always milled the heads flat, so you can get a bit more compression that way also. If you mill .020 off your heads, it should put you around 64cc chambers. If you swap for 273 heads and mill them .040 you get down to 57 cc chambers. I would guess casting #302 318 heads would be similar. Where did you find the marine head gaskets at .015 thick? Sounds interesting.