Compressed head gasket thickness for the following gaskets out of the GMPP catalog:

LT1/Aluminum heads = .050
LT4 = .043
LT1/Iron Heads = .028

 

So, some say theirs were 54cc and some say theirs were 58cc and some say theirs were 55-56cc. Can ther really be that much of a difference in the same factory LT1 heads? Guess so.

My motor just went back together, I wanted to calculate my compression ratio with the new pistons, but it looks like it could be anywhere from 11:1 to 11:8 depending on the size of my stock combustion chambers. Oh well....

 

I have cc'd several sets of unmolested LT1 heads, and all are around 54cc. Like Chuck says, they vary a bit though.

On a related note, I am playing with a set of em that I decked to 49cc. Decks look thick enough, and aren't quite into the seats. I think I'll try em on a stock short block just to be sure .

 

My stock LT1 heads cc'd at 54.5 cc's

 

Eww this ain't cool. I figured all my math with a 54cc head, knocked down to 53cc with .006" shaved off.

The 1074 gasket is .039", w/ a 4.125" bore diameter.

 

FWIW,I checked one chamber on mine.Nearest I could figure was 56cc's.

 

GM blueprint specs call out 54.0 for LT1, and 54.4 for LT4. As noted above, extra compression of LT4, comes from less volume gain, from smaller valve reliefs in piston crown.

For those that race in 'stock' classes, in order to wring the most power/torque out of their engines, thru 'blueprinting', above specs mean minimum specs. OEM as a rule, leave extra stock on heads and block, so to error, would be to error on the conservative compression side. Has been this way since small blocks left the factory without oil filters. This will explain the variation of volume findings from 54 to over 57 on the LT1 head. I personally, have not checked enuf heads of various years, from '92-97, to get a 'handle' on any volume trend, for any given year.

 

54cc for the lt1 and 54.4 for the lt4. check this out