Head milling ?

[2QUIK4U]

I am thinking about having the heads milled to bump the compression when I do the DOD delete cam install. How much should I have them milled? I was thinking .020 but Im not sure.

[laserred]

I think .020" came to around 4ccs on my brother's heads. He's got a self-made L92/L76 setup in his Camaro that was done before our cars made it here- LS2 block, L92s and L76 all from Scoggin Dickey. With .020" off they were 66cc. Only place he dropped the ball was not having the block decked, pistons are .020" in the hole, so with .027" gasket compression is only 10.6:1.

[gr8lover]

so are the pistons .020" below the deck or .005" above it? not sure I understand... ((.oo5" from one of yuor other posts...)

[laserred]

Ours should be around +.005", my brother's was a Lunati crank/rods and Mahle piston setup, not the same as ours.

[Brian@RPT]

The next build I am going to do is a 0.046" Head Gasket an take 5cc off the heads. The general rule is 0.006" for every cc. The last measurement I took of the piston travel was 0.007" above the block deck surface. That should put you at 11:0 to 1. I have done this to LS1 Corvettes and the torque is very much improved and these were autocross cars as well.

[DarkPhoenix]

Get a cometic .030 head gasket and that should take you from 10.4 to 1, to about 10.9 to 1, no milling required. Would definately help out in the power department, probably have to double check the ptv on an aftermarket cam.

[gr8lover]

Whatever you do... becareful that if you mill and raise your compression... that you do it or verify that the correct amount was removed...... otherwise..... if you then decide to supercharge it..... on a "over-milled" head then your engine will go BOOM!!!!!!

I originally was going to just go cam and was told I had ".025 removed from deck".... so that would be somewhere around 10.8 to 1..(which would be ok for a supercharger).. however it now looks like they removed ..043" if block was mean.... I checked and my heads are now 63cc with .042 removed... thus giving me a 11.4 compression.... not so good for supercharged!!!!!! ARGGGGGGGGGGGG..................BOOM ... BOOM...............so I guess what I am saying is have the work checked!!!!!

[laserred]

Get a cometic .030 head gasket and that should take you from 10.4 to 1, to about 10.9 to 1, no milling required. Would definately help out in the power department, probably have to double check the ptv on an aftermarket cam.

This would be bad, BAD, BAD with our motors. Brian said his were +.007, most are around +.005- a .030" gasket will definitely get you into at least piston-to-head contact, and likely PTV as well. .023 clearance from piston to head is INSANE unless you've got every single piece micrometered out, and won't ever overrev a motor. To be on the safe side, you should never go tighter than about .035" on PTH, just because you have tolerances in manufacturing, oil thicknesses, thermal expansion, etc.... this is bad JUJU. Like Brian said, get a .045 gasket and call it a day. That should be upper 10s in compression, then have a few CCs milled off the heads. 11:1 or a hair over. All will be well with the world.