does any one know what the combustion chamber size of the LN3 cylinder head (NA :?: engine) and also the combustion chamber of the L67 cylinder head (SC series1)? Or better yet a place on the net where I can go to find these specs. I am in Iraq so going to the local machine shop is out of the question.

I have all the specs at home. I can get back to you tonight. Shoot me a PM to remind me.

I have GM'* master prints for the S1 L67 heads.

If I bolt on my LN3 head to my L67 will I increase, decrease, or not affect the compression ratio

I can't tell you that. I don't have the master prints for the LN3. I'd suspect absolutely zero change.

If you want to change compression, shave the heads. I wouldn't suggest that though. There are much easier ways to do that, like raising your effective compression through boost.