Its a factory stock ZZ4 shortblock so the piston is some measure down in the bore (dunno the exact measurement) and the pistons are flattop with valve reliefs. The headgasket has a .028 compressed thickness. The cam specs out at 224/230 .574/.577 112lsa 108 CL. I want to mill about .018 off the heads since they are being ported now and they had 64cc chambers. I want to stay around 10:1 compression. Do I need to worry about piston to valve clearance?

 

I would check it just to make sure. I didnt have any clay so I used a cube of unchewed bubble gum to do mine. Worked well and I was able to rest easy then when I fired it up.

 

Yep, like what he said. It's always a good idea to check. Even if you're almost positive it's ok. Only takes a few minutes and little effort compared to money and lots of time later if it actually smacks a valve running.

My guess is you'll be fine. I had over .600 gross lift after rr upgrade on mine with a 0.015 compressed thickness gasket with 76cc heads and I didn't touch any of the clay on my valve reliefs at all.

If the heads are apart now you could just have #1 put back together for you to check. No need to reassemble the whole head.

Or you could just chance it and check after there milled. It would really suck to find out by some rare chance you do not have the clearance need'd. Especially after spending all that money for the port and mill job.

 

as a rule you won't see any interferance problems till around .65 lift, but there are too many variables to know for sure without checking.