Alright, ive got a 76cc head and an 11 cc dome. yes i know i should have gone with a 64 cc head and a flat top or small dome, but thats all i have so i've got to deal with what ive got. Right now, my deck height is .019 and i am wanting to use a .015 head gasket. = .034 piston-head clearance. Also , i am going to reshap my pisotns taking 2cc off them .Now my forged srp pistons call for .040 clearance. I want to wrap out to 6700rpm, and have 4340 rods, and a 5140 crank. Since im not going to wrap that far, is .006 going to make THAT big a deal, or is everything going to explode.

 

.040" has been considered a conservative safe minimum. Actually, quite conservative with steel rods that stretch very little in comparo to aluminum rods. You'll be fine. I (personally) consider (for you rev range) .025" a safe bare minimum with steel rods.

 

has anyone had any bad experiences using too thin a head gasket??

 

I have and they blew on me within a month of nonhard driving.

 

That's a question that's not gonna get accurate answers. Sometimes you have a gasket failure and it's not always the gasket's fault.... the gasket is always going to get the blame though.
I've used em as thin as .025" without problems. Main thing is the deck surface/head surface flatness and finish. I'd say that they are paramount in the life of a gasket.

-Mindgame

 

well i was meaning like the piston touching the head.

 

Ohh if thats what you mean then don't worry at all, aslong as you have quench of any sort, it only gets higher with more heat with heads expansion.

 

As arnie said, anywhere from .035-.040 is very safe territory. It's not just about rod stretch though... piston rock is a factor in there too, and to a lesser degree, I'd say that crank torsion in really high power cars could be a significant factor.
Shorter piston skirts and tighter ring packs allow for a little more rock. Only a problem though when you start trying to go really tight, like less than .020. Seen guys do it (real tight) with the piston out of the hole but that's really pushing things, considering the bang (pardon the pun) for the buckage.

-Mindgame