From what I have read, they seem to be any were from 70- 69 CC depending on The L92 casting numbers you got...

Known head casting numbers so far...

5364
0821
821
823

823's appear to be the most upto date Gm Casting in stock forum...

 

Good find. I wonder what kinda CC i am looking at if i have them milled, .010, .020, or .030. Looks like im headed over to tech.

Dustin

 

I think it will still be about .007 for every 1 CC you want to remove from the head. Any compatent shop should be able to get you right were you want to be.

 

Very interesting.

Dustin