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There are lots of variables in figuring compression and more in estimating detonation potential... but in your case I'd say no way on pump gas.

With 80'ish cc heads and 4.15+ stroke you will just about always need a decent size dish piston for pump gas. As a guess, you are around 11.5 CR with the flat top. With a smaller performance cam, you should be at 10 or maybe less depending on quench for pump gas.

I'd send it back and get the dish piston. If you have measurements on your engine - deck height, rod length - and know the piston specs - compression height and dish or valve relief volume - CR can be calculated more accuratly.

Bottom line, flat top on a stroker is normally a race gas only setup.



I have a dish in my Diamonds in a 470"(low deck) with Eddy heads at 84cc...puts me at 10.2:1 which works great on pump swill.