Join Date: Jan 2008
Location: Marlborough, MA
I noticed no one answered your question about milling the heads. Yes, as a matter of fact if you can mill them a LOT that is a good thing. Many on here have done it, Rick G - which your new cam specs look very close to - recommended a .035" mill which is what I did. Our motors are a bit low on compression, as they are using heads designed for a 6.2L on a 6.0L. So in the LS3 the CR is 10.7:1 while ours is 10.4. Once you increase cam timing you are bleeding off more cylinder pressure at low rpm due to later intake valve closing, which can in particular make for a soggy bottom end. That is why you will usually seem recommended CRs rise as cam timing rises.... So in short, yes, with a cam you want more CR. Milling .035" took my CR up to 11.1:1. And I love it, lots of part-throttle "pop" at low RPM. In theory a higher CR should make a touch more torque and power. Now, the downside is less piston-to-valve clearance. I measured mine and I'm around the minimum recommended. There is no problem sealing the intake - confirmed with Rick and I've had no problems sealing (traditionally if one mills heads that much one would need to get their intake manifold angle milled).
2009 SRM G8 GT, GMPP CNC heads milled .035", RCR backcut intake valves, RCR Lunati 219/223 .612/.615 112+1, PSI 1511ML springs, Ti retainers, BTR 7.375 pushrods, Straub trunion bushings, RCR Airram intake, IWIS chain, Melling hi-vol hi-pressure oil pump, oil bypass blockoff, LS7 MAF in Spectre 4", Blox velocity stack, Rotofab, Kooks 1-3/4" LT's, Kooks catted X, Hooker Maxflow axlebacks. 426/383.