On a stock C5 I am looking to get good heads such as the stage 2.5 5.3L heads or cnc'd ls6 heads and a cam like the ms3. At least mid 230's with about .600" lift.
Main question is how much can i mill these heads to up my compression, i am trying to figure out if i can get 12:1 or higher for max power with E85?
High lift cams limit the milling?

 

You are not going to be able to mill the heads if you go with a ms3, it is pretty close the way it is with stock heads

 

My H/C in sig, and Im pretty much stuck with the cam I have due to PTV issues.
TSP can recess the valves in the heads in order to be able to run a larger cam with milled heads. Give them a call!

 

I milled my Dart 205s on my Z06 about 30 thou. I was running 58 cc chambers in those heads with a Futral F14 cam without any issues.

 

With a GM casting you'll be pressing your luck to mill them anymore than about .005" (clean-up milling only)! We're able to setup the 5.3L heads for the MS3 camshaft by recessing the valves a few thousandths like stated above. The 5.3L heads bump your compression up to about 10.8:1 or so. There's not really any more room to grow there without flycutting the pistons. I would assume you could just run more timing with the E85 without all the extra compression, but sine we cannot get E85 yet we have not been able to test it. Sorry I can't be of more help in that area.

Let us know if we can help with your build!