Need help with Compression Ratio
Thread Starter
Racer
Joined: Sep 2007
Posts: 369
Likes: 1
From: Calgary AB
Need help with Compression Ratio
Completely stock, expect for new AFR 205's with untouched 66 cc chambers. Not sure on what Gasket to use, but probably go with .04 thickness Cometic Gasket.
Thanks,
Matt
Thanks,
Matt
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
You can use all the factory specs and change the gasket thickness with a compression ratio calculator to find your new compression.
http://www.rbracing-rsr.com/compstaticcalc.html
http://www.rbracing-rsr.com/compstaticcalc.html
Tech Contributor
Joined: Sep 2005
Posts: 1,731
Likes: 82
From: New Market AL
A dynamic compression calculator factors in your valve opening and closing events, which is useful to know when selecting a camshaft.
For your stock LS1 with 66cc chambers, 3.9" bore, 3.622" stroke, 6.098" rod length, .006" piston out of hole, & zero dish or crown:
10.36 with a 0.056" MLS head gasket
10.76 with a 0.040" Cometic head gasket
The .040" would be a much better choice for you, with the small bump in compression and the tighter quench volume. If you let me know what engine and year you have (LS1 or LS6) I can also tell you the dynamic compression for a stock cam with those heads.
For your stock LS1 with 66cc chambers, 3.9" bore, 3.622" stroke, 6.098" rod length, .006" piston out of hole, & zero dish or crown:
10.36 with a 0.056" MLS head gasket
10.76 with a 0.040" Cometic head gasket
The .040" would be a much better choice for you, with the small bump in compression and the tighter quench volume. If you let me know what engine and year you have (LS1 or LS6) I can also tell you the dynamic compression for a stock cam with those heads.
Thread Starter
Racer
Joined: Sep 2007
Posts: 369
Likes: 1
From: Calgary AB
A dynamic compression calculator factors in your valve opening and closing events, which is useful to know when selecting a camshaft.
For your stock LS1 with 66cc chambers, 3.9" bore, 3.622" stroke, 6.098" rod length, .006" piston out of hole, & zero dish or crown:
10.36 with a 0.056" MLS head gasket
10.76 with a 0.040" Cometic head gasket
The .040" would be a much better choice for you, with the small bump in compression and the tighter quench volume. If you let me know what engine and year you have (LS1 or LS6) I can also tell you the dynamic compression for a stock cam with those heads.
For your stock LS1 with 66cc chambers, 3.9" bore, 3.622" stroke, 6.098" rod length, .006" piston out of hole, & zero dish or crown:
10.36 with a 0.056" MLS head gasket
10.76 with a 0.040" Cometic head gasket
The .040" would be a much better choice for you, with the small bump in compression and the tighter quench volume. If you let me know what engine and year you have (LS1 or LS6) I can also tell you the dynamic compression for a stock cam with those heads.
Tech Contributor
Joined: Sep 2005
Posts: 1,731
Likes: 82
From: New Market AL
I have struck out trying to find the .006" lift duration numbers for a stock 03 LS1 cam. If I was to guess, you will have a DCR around 7.9 to low 8s with those heads and a stock cam. When you pick out a cam you should bump that DCR up around 8.5 by adding more duration.
Here is a screenshot of the Excel spreadsheet for my LS1, AFR, Comp Cam build to calculate DCR. You can download this spreadsheet by doing a search for PianoProdigy on LS1Tech.
Here is a screenshot of the Excel spreadsheet for my LS1, AFR, Comp Cam build to calculate DCR. You can download this spreadsheet by doing a search for PianoProdigy on LS1Tech.
Last edited by chevy406; Jun 24, 2009 at 03:56 PM. Reason: added spreadsheet
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