I am getting a LQ4 and will be changing heads to up the compression. I have a set of LS6 heads that I can put on. Was thinking about ported 5.3 heads and wondered what the compression would wind up being on the LQ4 with LS6's versus 5.3's. Of course I could mill either one but don't want to run into PTV issues. Anybody know what the compression would be with the LQ4 shortblock with LS6 65cc, 5.3 63cc or mill either one to be even tighter? Anybody got any numbers to through around? Thanks

 

What if I run the LQ4 shortblock which had 9.4 to 1 and used the LS6 heads and a .040 head gasket? Anybody know what the compression would be. I would like to get in the upper 10's with the compression.

 

LS6 with 0.040 = 10.57:1
5.3 with 0.040 = 10.82:1
LS6 with 0.056 = 10.17:1
5.3 with 0.056 = 10.40:1
Heads milled to 58cc with 0.040 = 11.37
Heads milled to 59cc with 0.040 = 11.22
Heads milled to 58cc with 0.056 = 10.90
Heads milled to 59cc with 0.056 = 10.78