[LTK]

Could anyone give me the correct factory compression ratio for a 1979 C E code LS6. I understand that the original motors were 11:to1 but I have been told that the later ones were 10:1. Please help I can't find any thing in the search area.

 

[Guest]

I bought a new LS6 for one of my boat customers, compression was advertised as 10 to 1, it measured 9.85 to 1. This was in 88.

 

[Guest]

Later LS-6 crate motors (Code XAA) had an advertised compression ratio of 10.2 to 1. This was because Chevy switched to open chamber heads on the crate motors, though i'm not sure what year that started. Don't know about 79 CE's.

 

[Dave Birdwell]

Here's an interesting question....How do you know it's an LS6 CE motor???
Follow along here a minute...warranty on 1970 cars, 12 mo./ 12,000 miles. If a new LS6 was delivered at the latest date possible, say a left over car at the end of the 1970 model year, might be sold on January 1st, 1971. The NEWEST the CE motor could be dated would be late 1971. If the motor you have was cast in 1979, and has a CE code, it is not an original LS6 CE motor. It is more likely a truck CE motor that someone rebuilt to LS6 specs.
The only other possibility is the casting date is actually 1969. What is the casting number of the block???

 

[plain 69]

10.2 to 1 is correct for a LS-6 crate engine.