Head milling question

[ScottieB007]

I have a 1977 318 that's going into a truck , I have got everything as close to blueprint as I can , my question is I'm to the point now of CC'ing my heads one come out at 68 cc the other came out at 67 cc factory spec is 63 cc for those heads , if remove the roughly 5 and 4 cc from each head which is like 30 thousanths will I have to mill the intake side of the head or will I be finebecause it's just going down to factory spec , I'm using a performer intake and have had the decks of the block cut smooth which might have removed 10 thousanths from each side of the block thanks for any help

 

[Marcohotrod]

the factory spec was smaller than any head ever came from the factory. if you cut off .030" you will need to mill the intake side. I would cut around .007" of 1 head and .012" of the other, then the intake sides will not need to be cut.

 

[JBurch]

Rule of thumb, though this is not absolute, is for every .010 off chamber face, cut .0095 off intake face.

When I say not absolute, there are those who have claimed to have successfully milled .030 (or just a bit more) and not had intake fitment problems.

I see you had the block decked. That will also influence intake fitment; it acts just like cutting chamber face.

Good luck! Measure twice, cut once...................

 

[ScottieB007]

The block decking just was minimum to make sure everything was flat nothing more I guess I'll have them clean up the head surface to what ever makes them true and just tell them to stop at ten thousandths

 

[540slant6]

I milled my 318 heads .030 on the block side and went .020 on the intake side. Everything fit like a champ. My teener loves to rev and hits 6,500 RPM on the regular.

 

[rumblefish360]

The specs you read in a book, Chiltons or the NHRA's are not accurate on the "As delivered" production head you actually find in use. There closer to the minimum size spec.

 

[Sedanman]

Not to hijack your thread but... I'm picking up a set of 0.30 milled (block side) X heads (63cc's) and will have to figure out an intake for mine as well. I'd rather not have to mill an intake if I don't have to. Recomendations?

 

[rumblefish360]

If your heads are milled to meet a certain compression ratio, then your answer is probably, No, nothing you can do but mill the head IF the intake face of the cylinder head can not be milled to fit the intake.

While that maybe possible, the bottom of the intake may need to be milled to allow it to sit down all the way.

 

[yellow rose]

There are too many variables involved to say how much you can take off before you have to machine the intake face.

So, you must ALWAYS mock up EVERYTHING before you do final assembly. Check it all out.


Don't forget, you can only machine so much off the deck and heads and intake face without cutting the end rails.


Always verify BEFORE assembly.

 

[nm9stheham]

Not to hijack your thread but... I'm picking up a set of 0.30 milled (block side) X heads (63cc's) and will have to figure out an intake for mine as well. I'd rather not have to mill an intake if I don't have to. Recomendations?

IIRC: Per the Mopar Performance book, if you take off half of the depth on the intake surface of the heads that you took off of the block surface. So, for .030" off of the block surface, take .015" off of the intake surface.

I'll double-check that publication tomorrow when I get home from work travel to be sure I remember it right. (Which I may not!) Geometrically, it makes sense to take off 1:1 block:intake surfacing.

EDIT to correct the above: I was wrong...(so much for my memory!). Take of .0095" from the intake surface for every .010" from the block surface. Not sure where I got that wrong idea...

 

[JBurch]

Not to hijack your thread but... I'm picking up a set of 0.30 milled (block side) X heads (63cc's) and will have to figure out an intake for mine as well. I'd rather not have to mill an intake if I don't have to. Recomendations?

Do you know if the intake face has been milled when the chamber face was milled? May or may not have fitment issues. If you have a set of crushed head gaskets of the style you are going to use in the future, slap them down, slap the heads down, put an intake down and see what it looks like........it's the ONLY way you'll KNOW for sure.