My 09 4.8 has the 243's and I have been researching cams, and trying to calculate how much to mill my heads and what gasket to run for optimum static and dynamic comression ratio. I always was under the belief that the 4.8's and 5.3's from 99 were 9.5:1. I found a spec sheet that says my engine is 9.1:1??

http://www.gmpowertrain.ca/Product/4...Y2%20Specs.pdf

So with that being said, I will likely end up milling the heads .035~.045" depending on what gasket options there are. I have see plenty of LS1 gaskets with a 3.9ish bore, but is there a small bore gasket for the 4.8's and 5.3's in a .040" thickness? I want to try and get the SCR to about 10:1 and the DCR to about 7.5~8ish.

Any input greatly appreciated!!

 

the cometic .040 3.91 gasket will work

 

Yeah, thats probably what I'll go with. I was hoping there was a gasket with a lil smaller bore that would help with the cr.

 

even if you could find a gasket that was 3.8 bore the difference is compression is only ~.05 from a 3.91 using .040 thickness. call cometic up. they can make you any gasket you want for the same price.

 

I just don't get how its 09.1:1 my truck 799 heads and flat top pistons came with 9.9:1

 

I don't know man, but just milling and bumping the cr how it sits would be a signifigant bump in throttle response and grunt.

 

Its a well noticeable difference when I milled my heads I went from 9.9-10.5 and put the 217/223 over the 212/218 and I went from 8.97-8.62 on the 1/8 mile.. and with same tune...