Hangman

iTrader: (1)

I'm trying to raise the CR on my 408, with the 68.5cc on the ls3 head I'll have CR of 11.2, if I mill those .03 I'll have 11.5, however the GMPP cnc ls9 head has a 66.5cc, can those be milled down .03 as well? I know about the titanium valve issue, and Del West will refinish them for free, I don't mind paying the $150 difference per head to increase CR, get a better quality head, and lighter valve train.

Mercier

iTrader: (15)

I just went through this with a set of LS9 CNCs. I was also fooled by GM's published numbers. They actually list both the 66 and 68 number in the GMPP catalog so I cc'd them myself. They are 68.5. Short version, I milled .025" (this is what I asked the machine shop for; I assume that is what I got) and got to right at 64cc:

Initial cc

Milled

Final cc