skipgsxr

I am doing a head cam swap, I am fly cutting so I want to bump the compression. I am doing a ms4, with LS6 heads. I have .040 gaskets. I am thinking about having them cut @ .030, is this too much? i am looking for @ 12-1 cr.

proelky

iTrader: (13)

I would look at a compression calculator first. Next, after you flycut do a clay check to make sure you have proper PTV clearances (.030-.040). It looks like you'll need to choose a little smaller cam, and mill the heads if you're using a stock piston. The highest compression you can get with a stock piston is right around 11.1 (using a .031 cometic, and milling the heads). If you do choose to mill you will need to back cut the valves, or flycut. Regardless, you're limited on compression unless you change something.

snake charmer

iTrader: (118)

i dont think a ms4 will clear with it milled that much . i clayed a set of 243s milled .021 with a 236 /230 on a 114 . the clay had about .020 on the intake the exh. was .120 and would have worked on the exh. side just not the intake . just the intake valves would need to have nbeen cut . though it was a custom cam . i went with something smaller and proven a 224/228 and might of been able to mill the heads another .007-.014 .

skipgsxr

I am flycutting, so PTV clearance will not be an issue. So aside from PTV, there are no major concerns?

snake charmer

iTrader: (118)

not really just be sure to clay them and make sure you dont cut them too much .

RoDan

I would seriously use a DCR/CR calc and figure out where you stand as far as compression and what not and what your DCR will be so you can run pump gas. You can also play with gasket thickness to get your quench right also. Should be between .035-.045