How much head milling?

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valiant1966

valiant1966

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I am building a 318 to replace my slant in my 66 Valiant. The engine is a 1970 with 77-86 heads casting #4027163. It will have a 4 barrel and cam with 421/444 lift. Bottom end is all stock. The heads are ported, polished and gasket matched.
My question is: How much can I mill off of these heads without getting into having to mill the intake sides of the heads. I am thinking that the factory gasket(steel) was about .020 thick and the gasket I am using(it came in the gasket set) is a Felpro 8553PT which will have a crush thickness of .039-.040 so I am sure I can mill .020 off but surely I can go a little more without having to make adjustments elsewhere. Thanks for any help.
 
The short answer, in my mind, is none. I would always mill .0095 off the intake for every .0100 off the block side. Most shops will mill up to .020 for the same price. This is really important with the steel shim intake gaskets. All the Gasket Manufacturers count on this relationship. Thicker fiber intake gaskets are more forgiving. Can you do as you say, and get away with it? Probably. I think the original head gaskets were closer to .030 from the factory, but don't know for sure. Once you square everything the heads tend to seal really well.
 
Actually the metal gasket that came out was only .018 thick so if the new gasket has a crush thickness of .039-.040 isn't that going to have the head sitting about .021 to .022 higher that before which throws off the intake side anyway and lowers the CR?
Just "seems" like simple math to me but maybe not. Where am I wrong?
 
valiant1966 said:
Actually the metal gasket that came out was only .018 thick so if the new gasket has a crush thickness of .039-.040 isn't that going to have the head sitting about .021 to .022 higher that before which throws off the intake side anyway and lowers the CR?
Just "seems" like simple math to me but maybe not. Where am I wrong?
Click to expand...
and effect push rods too...
 
From looking at my information, the stock head gasket measured .027 to .029 thick. Steel shim gaskets measured .022 to .025, referred as .020 thick. The Fel-Pro's were measured at .038 to .040. You should be able to verify stock head gasket thickness from NHRA blueprint specs. What intake gaskets do you intend to use? The Fel Pro's that came with the set? I believe Fel Pro adjusts or engineers their gaskets to work together. Have the heads been milled before or the block Decked? It is simple math, but it is very interrelated. It costs me $70 to mill either Intake or block side. I do both, that way the head is what everyone expects. No problems.
 
The engine has never been apart before. The crush thickness of the Felpro is .039-.040 according to Felpro. Yes, the gaskets are all the ones that came in the set. So, am I correct in thinking that the head will set higher with the gasket being thicker. And, isn't this going to affect my CR and push rods?
 
You are correct in that it will set about .010 higher than stock. I believe Fel Pro adjusts their intake gasket to allow for the head being .010 higher. Do you have 2 sets of heads? CR ratio will be affected but not that you will notice. I like Fel Pro gaskets they should seal up nice. There should be enough preload in the lifters so that the push rods should be good to go.
 
Thanks for all the input. Yes, I do have 2 sets of heads. Why do ask? I have the original heads that were on that block but the valve guides were really wore so I found a set of really nice heads that really need nothing for a great price. Much cheaper than having guides installed. Dennis
 
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