hey guys pulled the heads off my car today to track town a noise in the valve train and while there off was thinking of having them milled while at the machine shop but dont know how much i can or should mill them? .020? 030?

how much HP is bumping compression worth? want to stay pump gas friendly also

engine specs
BTR Stage II Cam 227/234 .614"/.576" 113+2ported
dual 650 springs
ported fast92 intake
ls2 TB
powerbond 25% under drive pulley
vararam ramair & power duct
TPS Lt's off road X
stock bottom end
7.400 BTR pushrods

 

Stroker87 just a thought here, have you considered going with a thinner head gasket instead of milling the heads. The reason I ask is if you mill the heads it will only make the CC smaller, if you install thinner HG it reduces the entire diameter of cylinder bore (not making bore smaller, but loosing metal of complete bore dia. Not just small cc area), which in effect will raise compression. The benefits of that is it's cheaper then milling and for every thousandth you loose on gasket thickness will raise compression at a higer rate than every thousandth you mill off heads. I don't have the exact numbers here but for example only, lets say a .014 thinner gasket may yeild a .5 in compression bump and you may have to mill heads .030 for same result. When you mill heads alot you change angles for sealing surfaces like the intake. If you mill alot would that make the intake to head surfaces off a bit? Maybe not to point of sealing issues but the more you take off now, may limit room for correction of head gasket surface later if you have to mill for flatness on later builds. I did this on my harleys to bump compression over milling heads. I think it's similar to decking a block, much more efficient to raising cr than cutting heads.

 

DVUSz06, this is why i'm posting to figure out the best way to do this

 

Rather sure it's .050 raises compression one point. I'm fairly certain running cosmetics (.040) and milling .020 will net you approximately 11-1 compression.

 

i found out from TSP the heads was milled .010 when they was ported they said to clean them up, from what i'm reading on the internet it might be better to just use a .040 thick gaskets. the machine shop wants to know deck height i'll be figuring that out later tonight

 

Cool, keep us updated on what you decide

 

i'm clueless at this point!

the pistons sit about .009 out of the block so Bill (guy at machine shop) said go with stock gaskets (.051 think) the heads are already .010 milled so really confused at this point, do i just leave thing be or????

i wanted to get the quench right but really not sure at this point if its ok or not if i leave the heads alone and put back stock gaskets

 

Strocker87, you can check out some cr calculators on the net, you can play with the numbers and see what makes the cahnges you want. I would target a DCR of 8.2-8.5 (good street performance DCR) race gas you can run closer to 9:1 but that be pushing for pump gas, and quench from .045 down to .035 to safely be able to run 93 octane fuel. Best performance closer to .035 quench.
Thats what I do when planning a build.

 

I would listen to the guy at the machine shop. There are easier ways to get a few more ponies.

 

IIRC 0.054" is the stock compressed thickness of the gasket. I wouldn't go any thinner on a graphite gasket. MLS gasket would probably be ok, but some LS1's require a graphite gasket.