what is the compression ratio of a stock LS1? so far i have seen 10 to 1, 10.25 to 1, and 10.5 to 1. which one is it. i have also notice that there were two types of head gaskests used on the LS1. 1997-2001 LS1 used these head gaskets 12498543 with a thickness of .056 and 2002-2004 these head gaskets 12498544 with a thickness of .06. it doesn't say bore on either one. but i know there must have been a compression ratio change because of the change in thicknesses in the gaskets. it would really help if i knew the real compression ratios of the LS1 over its production years.

 

http://www.smokemup.com/tech/ls1.php

 

LS1=10.1
LS6=10.5

I know that in 2002 the head gasket changed, but I didn't think that it affected the compression ratio.

Also, I don't agree with some of the specs on that "smoke em up" page.

 

ok...so someone isn't telling the whole truth about the LS1 and i suppect its GM. ok i know that the stock gaskets used have a compressed thickness of .056". now basiced on that and the compression ratio of 10 to 1 the bore of the gasket should be 4.35" which is gigantic. now if GM used the same gasket on the LS6 which i think they did the LS6 should have a compression ratio of 10.25 which i know it isn't. now i have read that the compression ratio of the LS1 is 10.25 to 1. i think the 10.25 to 1 is the correct compresion ratio. using this 10.25 to 1 and the .056" as the compressed thickness of the head gasket the bore works out to be 4". now a bore of 4" and a compressed thickness of .056" works with the LS6 giving it a 10.5 to 1 compression ratio. so in i strongly think that the stock bore and thickness of a stock LS1 are 4" and .056" respectivily

 

https://ls1tech.com/forums/new-ls1-owners-newbie-tech/213148-jrp-s-faq-commonly-asked-questions.html

https://ls1tech.com/forums/showpost....9&postcount=11

https://ls1tech.com/forums/showpost....6&postcount=27

https://ls1tech.com/forums/showpost....81&postcount=3