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07-25-2018 04:08 PM #2
What would I do? Regardless of open or closed, I'd look for the smallest combustion chambers I could find to raise static compression ratio if I didn't want to change pistons.
3856206....65-66...oval..CLOSED..396, 97cc chamber
3872702....65-66...oval..CLOSED..396, 427, 98cc chamber
3904390....67......oval..CLOSED..396, 427, 98cc chamber
3909802....67......oval..CLOSED..396, 427, 101cc chamber
3917215....67-68...oval..CLOSED..396, 427, 101cc chamber
The 702's and 390's are probably the best flowing out of the bunch. If you can afford it, change valve sizes to 2.25"/1.88" on the 390 heads or 2.19"/1.88" on the 702's, although it would probably be about the same money to install some decent pistons and make the same horsepower with more static compression ratio as you could with larger valves.
The cranking compression will be dependent on the static compression ratio and the closing point of the intake valve. It's a complicated balancing act and I suspect that the front runners have spent plenty of dough to find the consistent 180 psi cranking compression and the correct vacuum reading (which you did not list).
.PLANET EARTH, INSANE ASYLUM FOR THE UNIVERSE.
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