in reference to the new GM 480ci block, assuming a 4.125" bore, what would be the stroke and piston dish required to have a 454ci with ETP 255 LS7 style heads, to have a 10:1 comp ratio?

 

4.25 stroke. you would need 1.25in^3 (20.48cc) dish in the piston to get 10:1 compression. Your clearance volume is 6.31in^3 per cylinder. if the heads have 72cc chambers that is 4.39in^3 of your 6.31. Now your head gasket is going to be about .67 if you use .050" thickness.

Formula for what I used to calculate the dish size are....

clearance volume = [Vd/(Rc-1)]/8 = 6.31. This is the volume between the piston and combustion chamber to get the required compression ratio. dividing by 8 gets you the volume for one cylinder.

72cc*1in^3/2.54^3cc = 4.39in^3 this is the conversion from cc to ci for the cylinder head volume.

[PI*(4.125^2)/4]*0.050 = .668in^3 this is the head gasket volume.

6.31-4.39-.668 = 1.25ci

 

If you don't get a dished piston for your engine then your current setup will have a compression ratio of 12.21:1.

 

WOULD IT BE SAFE TO SUPERCHARGE THAT, AT 10:1CR WITH ABOUT 6-7 PSI. mY GOAL HERE IS VERY HIGH FLOW NUMBERS, WITH VERY LITTLE BOOST PRESSURES.

IN MY HEAD, AND TELL ME IF IM OFF THE MARK, BUT THAT COMBO SHOULD BE WORTH ABOUT 700-800RWHP, GIVEN A GOOD DRIVELINE