Originally posted by warmonger:
This is NOT a problem if it is done correctly. You shouldn't have to dish the pistons. Also, you don't want to go machining valve reliefs in stock pistons as these pistons are aged in the heat treatment process and you don't really know what it will do to the piston surface. It may be ok but then it may lead to greater rate of heat transfer to the piston body. It also may not have a beefy enough crown to take having four holes machined into them. You can get the later model pistons that have valve reliefs cast into them if this becomes a real issue.
In your case, it was one of three problems that I can think of:

1.) timed incorrectly
2.) bad or worn out timing chain/crank drive sprocket/tensionsers/guides. Any of these can allow too much slack. Also using the wrong tensioners on the chains
3.) machined too much off the heads and there is no longer enough clearance.

You can fix your valves and retime the engine, but use some modelers clay on the piston tops to see what the clearance is.
Let us know if you reused old timing components (not necessarily bad) or if you mixed and matched any components.
Let us know if you had the heads surfaced before installing them, and if so tell us how much was taken off. Hopefully if you did it wasn't some shop with a table sander that just slapped the heads on and then said "that looks about right" and gave them back to you.


I do plan to use some clay when I rebuild it this time. Kinger is the one that did the heads up for me. IIRC, he said he did deck them but I think only .002" and that was two years and 15K ago. I used all the same timing components from before (they only had 15,000 on the chains/tensioners and 1 hr. on the new guides. I verified timing on both banks when I built it up two years ago and turned it over by hand both then and now.

I think if I were off a tooth it would have bent more of the valves than 2 of 6 on that bank? Also, I did not remove the front bank and still had contact with (but not bent) two of the valves there as well.

As far as dishing the pistons, it's one of the ProStock guys from Dart that'll be doing it (for free) and I plan to have the pistons heat coated (along with the exhaust valve bores in the heads) again before they go back in. They are the newer (01) pistons with the reliefs in them. I'm running 3L valves in 2.5 heads. Could that be part of my problem?

I'll put holes in him!!