1980 Compression ratio calculation
Thread Starter
Racer
Joined: Jul 2005
Posts: 420
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From: Yerington NV
1980 Compression ratio calculation
Has anyone done or seen HOW the advertised CR on an 1980 L48 was calculated to 8.5:1 ?
I thought it was 8.2:1 for some reason, but the shop manual says 8.5:1, but in either case, I would like to know how that CR was obtained.
Any of your mechanical engineers with spare time on your hands?
My USARMY daughter is going to Iraq soon
& My USNAVY son is still out of harms way, so far! 
I thought it was 8.2:1 for some reason, but the shop manual says 8.5:1, but in either case, I would like to know how that CR was obtained.
Any of your mechanical engineers with spare time on your hands?
My USARMY daughter is going to Iraq soon
& My USNAVY son is still out of harms way, so far!
Le Mans Master
Joined: Apr 2005
Posts: 6,366
Likes: 432
From: Seattle Area WA
Well there is advertised compression by GM which is often .25-.50 higher than what the actual compression is/was.
Just do the math or use one of the online calculators available. If I plug in standard values such as a standard 4.0" bore, 76cc heads, a typical .025" GM steel shim head gasket with 4.1" bore, deck height of .025" and the 12cc dished pistons the resultant SCR is 8.27:1
Just do the math or use one of the online calculators available. If I plug in standard values such as a standard 4.0" bore, 76cc heads, a typical .025" GM steel shim head gasket with 4.1" bore, deck height of .025" and the 12cc dished pistons the resultant SCR is 8.27:1
Thread Starter
Racer
Joined: Jul 2005
Posts: 420
Likes: 0
From: Yerington NV
Cool! Thanks Scott, that was just what I was looking for! I am little confused about size of my pistons as I have dished, but they have the "fly" relief valve little grindouts.... so I am not sure what my cc should be, any idea???
Thread Starter
Racer
Joined: Jul 2005
Posts: 420
Likes: 0
From: Yerington NV
Therein lies the problem .... it is a remanufactured corvette motor (don't ask, long story - motor stolen by a tranny shop, shiester put in HIS camero motor while overhauling stock tranny), PO went out and got a remanfg "stock" 350 corvette motor and put it in ....
Do you still think the dished pistons with the fly relief valves are 12cc?? I have a picture of the pistons, if that helps any!
Do you still think the dished pistons with the fly relief valves are 12cc?? I have a picture of the pistons, if that helps any!
