Engine build on the brain

Hey OP, Is the 68 cc just a number you got somewhere for the chamber size, or were the chambers all measured and equalized to that cc number in the porting process?

I just ran your numbers. With the Icon 744's and standard LA deck height and rods, the piston tops end up at .012" in the hole, not quite zero-decked. Going with the 68 cc chamber size, and the Felpro 8553PT gasket at .051" thick, SCR is 10.6. For the Felpro 1008 at .039" thick, I get 10.9 SCR. Both gaskets have a bore size of 4.18" so there is more volume to account for if you have not done so. And I always add at least 1 cc to the eyebrow volume to account for crevice space down to the top ring.

I get 8.5 DCR for seal level for the thinner head gasket, and 8.3 DCR for the thicker one at sea level, using 68.5 for the ICA. At your elevation, both numbers are going to be a bit lower.

So you appear to be doing things right with the caclulators, but it is small details in dimensions that make a difference. (BTW, your posts of you input numbers don't show the entry data... just the final output data.)

As for acceptable DCR, 8.0 is a pretty common number to work to for a good build and paying attention to tune for pump premium. 91 Octane seems a bit touchier based on some reports here. I am fine there (even with my lazy tuning habits!) and have been up in the 8.3 range, as mentioned earlier. Now AJ and YR have managed to really work it up higher with more attention to details and fine tuning.

So no way I would go to dish tops.... the next bus stop on that road is more than a point lower in SCR and DCR.

OBTW, have the block sonic tested before that .060" overbore.