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Originally Posted by Jersyboyy
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Why the dome piston? To make up for the 72cc heads?
The overly large gasket bore will cause you to give up compression. If the bore is 4.030 and the gasket is at 4.200 you have 0.170 difference. Divide that by 2 and 0.085 would be the distance from the bore to the edge of the gasket. That is probably less than optimal. I don't know if that it would be problematic down the road or cause hot spots or other combustion issues, but if you haven't plunked down cash yet I'd talk to someone who does this for a living.
I don't know the overall combo, but if you have 72cc heads, why not run a good flat top pistion, with a more conventional 0.39 head gasket? Or have the heads milled to get the cc's down.
You mentioned being able to run on the street on pump gas. But the nitrous cam to bleed off cylinder pressure, the pulling timing to drive it on the street and the 0.061 head gasket are all crutches you would use to fix an existing problem?
A true 2 valve relief flat top with an 4.030 bore (-5cc for the valve reliefs), 3.750 stroke, 0.039 gasket (assumed gasket bore is equal to engine bore), with a 72cc chamber volume and a 0 deck will yield about 10.2+/- probably a tad less. Easily to do on pump gas without having to pull timing, run a nitrous cam (in a non nitrous appication I assume). If you milled the heads down to 68 cc you'd end up closer to 10.6 and still be good to go.
I'm confused on what parts you already have and what you are trying to accomplish? Best advice is consult a pro who does this for a living. The closer you get to the ragged edge the more important the details become and easier it is to waste $$$.
Good Luck
Chris