Quick question.

I use 10.5:1 pistons in my build but with a 1.3mm MLS HG, how much is my headgasket going to alter my Compression Ratio? As much as I really don't want to do the math to figure out the new combustion chamber volume, I figured someone else already has the answer lol.

Would the added 1.3mm of deck height also alter timing a bit?

 

Ok. Since no one was of help, thanks guys, I came up with the formula and figured it out. And this is actually really helpful when using a thicker than OEM gasket. When piston manufacturers calculate a pistons compression ratio that factor in the thickness of the OEM gasket. Which is .72mm for the evo 8. Which is what they use because it will have less volume thus higher CR. This is the formula I used.

(Pi x (bore/2)^2 x stroke)/1000 to get the displacement of 1 cylinder in cc's.

Then you need to find the volume of the thicker gasket the same way. Instead of "stroke" input the thickness of the gasket.

(Pi x (bore/2)^2 x gasket thickness)/1000

Now to find the compression ratio, you take your displacement and divide by the actual head volume. The actual head volume is found with this equation.

Displacement/Possible Piston CR + New Gasket Volume - 4(4cc is the volume of the OEM head gasket) = Volume of Head *Remember piston manufacturers calculate the CR of pistons using the OEM gasket.*

Now take your Cylinder Displacement and divide by the Head Volume to find your corrected Compression Ratio.

Displacement/Actual Head Volume = Corrected Compression Ratio

For me, 87mm bore, 100mm stroke, 10.5 CR, -12cc piston dome, and 1.3mm head gasket, I should have around a 9.8:1 CR.