Pick your Compression Ratio !
Thread Starter
Safety Car
Joined: Jan 2006
Posts: 4,598
Likes: 78
From: Miami FL
2020 C6 of the Year Finalist - Unmodified
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16,'17,'18-'19-'20-'21-'22
Pick your Compression Ratio !
I have been playing around with what I want to do for my Heads/Cam project next spring. One of the issues is, of course, compression ratio. Do I have the heads milled? How much ? ?
Do I use thinner gaskets? How much thinner ? ?
So I finally made this spreadsheet for use with stock LS2 short blocks, to ESTIMATE the compression ratio for various combinations. The assumptions are in the header.
The teal bars are the stock head gasket thickness (according to some) and the stock combustion volume in the head, based on the 0.052" stock gasket. The intersection is the stock compression ratio, 10.9 to 1.
Cartek, for example, provides a 0.030" mill resulting in a 61.5 cm*3 (cubic centimeter or cc) combustion volume in their Stage 2 and Stage 2X heads based on 243 castings. With the stock gasket, we can see that this will yield about an 11.5 to 1 CR.
Alternatively, using a thin 0.036" Cometic gasket with stock heads will provide about an 11.4 to 1 CR.
If you would like the underlying spreadsheet to play with, send me a PM. The attachment allows you to see the sheet a little larger.
Do I use thinner gaskets? How much thinner ? ?
So I finally made this spreadsheet for use with stock LS2 short blocks, to ESTIMATE the compression ratio for various combinations. The assumptions are in the header.
The teal bars are the stock head gasket thickness (according to some) and the stock combustion volume in the head, based on the 0.052" stock gasket. The intersection is the stock compression ratio, 10.9 to 1.
Cartek, for example, provides a 0.030" mill resulting in a 61.5 cm*3 (cubic centimeter or cc) combustion volume in their Stage 2 and Stage 2X heads based on 243 castings. With the stock gasket, we can see that this will yield about an 11.5 to 1 CR.
Alternatively, using a thin 0.036" Cometic gasket with stock heads will provide about an 11.4 to 1 CR.
If you would like the underlying spreadsheet to play with, send me a PM. The attachment allows you to see the sheet a little larger.
for the weekend ? 
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
My advice: If you run gas without Ethanol, go with stock compression for best power/timing without KR. If you run gas with ethanol, more CR will be better.
A cam effects overall dynamic CR far more than static CR anyway, so if your going with large overlap, higher static CR is good as well.
A cam effects overall dynamic CR far more than static CR anyway, so if your going with large overlap, higher static CR is good as well.
