Ok so im building a 5.3 and thinkin about boring it about .30 over with forged flat tops a few other go fast parts and a tsp 228r cam (.228 .228 dur. .588 .588 lift 114 lsa) I have a set of 862 heads 61cc and after a valve job probly 63 cc. I want to spray but also want higher cr what would be a good number to mill the heads to?

 

How much valve relief in the pistons?

If you can get at least 91 octane, milling the heads would help. I'd probably shoot for 59cc or so (probably about .020").

 

Haven't decided it depends how much i mill whether ill get relief pistons or not, but how much can i go and still put a decent shot of giggle gas on??

 

Short answer- the deck surface of the heads isnt the limitation your looking for (if you think they might get too thin), as I've seen sets angle milled 2 degrees (its alot, believe me) to considerably close up the chamber for N/A C16 race gas setups (think 14.8:1 compression with a 266/278 @ .050)...

What you WILL run into is IF you mill more than .035 off the heads (in my experience) you will have problems bolting the stock style intake manifolds back on. Now, if you have a aluminum intake, just mill half the amount off and it will be fine- IE: you mill the heads .040, mill the intake .020 on one side or .010 on each if your a real stickler.

Also, nitrous LOVES high compression. The more the better. The real limitation is the octane of gas your using. If your thinking of sticking with 91 octane, I wouldn't go above 10.5:1 with nitrous. To play on the safer side, stick around 10:1 or lower- honestly, who cares about 2% overall horsepower on a street car when you can just add another 25 shot to the mix?