hi.
does anyone know, how much the compressoin ratio is changed if a thinner head gasket is used.
I think the standard head gasket on my 88 is aprox 050 thou thick.
I have seen gaskets advertised at 030 thou thick.
so how much does dropping the head 020 thou affect the compression ratio.
thanks.

 

The change in gasket is about 3.6 cc volume in cylinder decrease, so assuming a standard bore and stroke, 3.75 X 4.0 and chamber volume of nominal 85 cc it would work out to about 2 points of compression, ie from 9.0-1 to 9.2-1, if my math is correct.

 

Bigboyz head porting has a calculator for that on there homepage.

 

I don't think it's a big deal on a stock engine but it will be a factor when selecting a cam, pistons, head work, ect. I used a .030 HG in my 95" build.
+1 on the BigBoyz compression calculator.