Engine gurus come here!

[DeWynter]

When calculating Compression ratio with a flat top piston do you minus 10 cc for the valve relief? I am using Engine analyzer Pro 3.3 to do a mock up of my 383 using stock TPI with effective RPM range of 1000-4500 as that is where they die. If I factor in a 60cc head with a flattop piston with -10cc valve reliefes and a .04 inch gasket and .025 deck hight I get 10.39 but If I dont use the -10cc I get 11.6 any help would be appreciated. I want to stay under 10.5 with the engine.
At 10.39 these are my results.
PkTq=460@3775rpm Avg=388 295@1000rpm 306@1500rpm
PkHP=388@4515 Avg=216

Engine is using 24lb injectors
edelbrock preformer centerbolt
hooker LT 1.75"Primary 28"long 6.5x3" collector

Assumes Blueprint and Balance.

[fastTa]

You need to look at your piston manufacturer's website and look up your piston part number. All of the relief cut volumes vary from piston to piston 0cc to -10cc . Is it a double-sided relief cut? Probably between -7 and -10cc.

Also when calculating static compression ratio, don't forget the gasket bore. It will always be larger than the actual cylinder bore and that will effectively lower the compression a tad.