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Yes, all things being equal, would it be better running a flatop verses the piston pictured above??

~thanks



That all depends on what compression ratio you need to be able to run the octane fuel you want.

If you choose a flat top and end up with 12.5 compression but want to run 89 octane fuel then yes you would need a piston that looks like the one above to get an octane friendly compression ratio and still have quench.



I'm running 91-93 octane E85 in my runner now. (jetted up my carb) I would like to run around 11.0cr in the new motor.



91-93 octane E85 ??? are you mixing it ??? I thought E85 was 105 octane ??

12.5 would be fine with E85 , where are you getting it near Fitchburg ? I want to run it in the engine I'm building but it looks like I'll have to run into Chelsea from Southern NH to get it .