Marine 273 build

I don't think those Egge domed pistons make the same compression as the stock hipo pistons. I did a side by side comparison of the Egge piston against an old TRW forged commando piston which is no longer made. The Egge had lower compression height and bigger valve reliefs. I think the TRW's were closer to the factory commando pistons.

http://www.forabodiesonly.com/mopar/showpost.php?p=1969625909&postcount=44

Besides the lower compression height of the pistons, deck height tends to be greater than spec and all the 315 heads I've cc'ed have come in around 63 cc's instead of the spec 57 cc's. Off the shelf head gaskets are thicker and have a larger bore size than the original factory gaskets. Add all this together and you have to do quite a bit of milling to get to 9.5:1.