I'm about to check my Piston-to-valve clearance and wasn't sure about something.

I've got the cometic head gaskets .040" thick. Is it ok to just snug up the head bolts and not compress the gasket when checking? If so, what is the UNCOMPRESSED thickness of these cometic head gaskets?

I'm using ARP head bolts if that matters any.

 

I want to say that snugging them up is fine - if you need the extra few 0.001"s to give you clearance then you've got much bigger issues going on. compared to the size of the desired clearances, a thou or two is going to be irrelevant.

 

Yep.

You can also use your old headgaskets (easier if you have MLS - but you're a 98, so you have graphite). Again, if .010" is going to cause the death of the engine, then you're probably going to need to flycut.

 

Ok. So your saying that at most the cometics compress .010"....

It's my first head swap, so I'm trying to be extra careful. And I'm am running a pretty tight clearance, so I want to be sure. 799's milled .025 with the .040 cometics.

 

No difference between stock and cometic is .011 or .014" compressed. Cometics don't really compress.

 

So long as the thickness is correct, you really don't even need to use a head gasket, you can use a spacer of correct thickness and tighten the head bolts finger tight. You do need to measure the thickness of the spacer accurately though, and too thin of a spacer is better than too thick.

 

I was told that the advertised thickness is the compressed value.

 

Also, call me a fool, but when I checked my PTV, i put the head straight on with no gasket, then added the compressed thickness. Of course I already knew that I would have miles of room, so I didn't worry about a valve hitting. If you just put the head on and carefully turn the motor over, I don't think it would destroy anything even if something did contact. Then like I said just add in the value for the gasket.

 

No, you should put the gasket on. Your way is a good way to risk mating surface damage (nick, scratch) and could potentially cause gasket leaks in future.

 

Advertised values are compressed. If you didn't destroy your graphite gaskets taking them off, they could be used to test fit. If you had stock MLS gaskets, you could just remove a layer to get the correct depth.

 

I guess I just got lucky. If this is the case, OP, I would not advise testing your luck.

 

It is not that it cannot be done, but why risk it? Safe practice=reliable product