I've been searching and can't find a very clear answer. I've got a lq4 that I'm trying to rebuild on a budget. I'm wanting to mill the heads some to bump up the compression. I've read info that says its fine to mill them up to .040 and I've also read its not a good idea to mill them at all because of ptv issues. I'm going for a cam no bigger then a 228. Would just like to clarify before I waste money milling these heads.

 

It will come down to cam lift, compression height of pistons, if they have valve reliefs cut in them, head gasket thickness and what you mill off the head. Give us specifics on the pistons/rods your using, what the lift of the cam you said is and we can help you out.

 

I was thinking a tsp224r .581 lift. All stock bottom end. Stock 6.0 gaskets.

 

If you have a lq4 bottom end then you have dished pistons so a cam with that amount of lift and those heads you could certainly mill them 0.040". Its always best to mock up the long block first and measure ptv clearence. There are a lot of variables that go into getting an ideal ptv clearence. Its also known as squish. Do some googling and search around the forums and you will learn a lot about it. Something to also keep in mind when milling a substantial amount from the heads or block is that you could come up with fitment issues of the intake and alternator/ps pump bracket that bolts to the block and the driver side head. I had auite a bit milled from the decks of my block and then roughly another .020" from the heads and i could only get 3 bolts in my alternator bracket. For the heads, if you have a good machince shop do the work, they can mill whatever is needed from the intake mating surface of the heads to offset whatever was taken from deck mating surface to allow proper fitment of the intake mounting holes.

 

I really appreciate the help man. Im planning on milling .030 off just to bump up the compression some. Trying to build this on a fairly tight budget.