TAPyvehc93

iTrader: (2)

This is on a 2011 5.3 with factory flat top pistons with valve reliefs. Running a 224/228 cam.

1ownerCHEVY

Ive milled .020 and had no issues. Just needed shorter PRs. Measure to be on the safe side

TAPyvehc93

iTrader: (2)

What size cam and do you know what that put your CR at?

dirt track racer 81

iTrader: (45)

I've milled .050 and been fine

bobfig

Mine are milled. 030" anything past that can start to get intake sealing problems.

TAPyvehc93

iTrader: (2)

Thats what I've heard. What did that put your compression ratio at?

bobfig

should be around 9.9:1 with the stock gasket (.051") on a 05 lm7 with the dished pistons. with the flattop pistons that should be in your truck you should already be at around a 10:1 ratio.

if you milled to a chamber of 61cc (~.020-.024") you would bump up to 10.5:1
stayed stock and got thinner .040" gasket and a .010" cleanup mill would net you 10.5:1 and have a better quench.

1ownerCHEVY

Not to highjack, but Im wondering the same thing about my compression ratio. I have an ly6 with the dished/valve relief pistons and 799s milled .020. Ls9 gaskets .051 i believe. Where would this put me at? 10.2?

bobfig

my calcumalator says somewhere around 10.5:1

Choda

iTrader: (1)

Good info here. So at what point did you guys decide on getting them milled? Sounds like you have aftermarket pistons. I have stock rotating assembly and about to tare mine apart for a mild build/update. Is it worth having the shop mill them down a bit or stick with the " just touch them to ensure they are flat " approach?