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Q. for engine shop owners/employees, head flatness?

Posted By: Flite_727

Q. for engine shop owners/employees, head flatness? - 04/18/12 09:12 PM

if you've got an alum. head that has never been warped due to overheating, & never been cut before, how flat & level does it need to be, before making a cut across the deck? i'm guessing due to normal circumstances such as thermal cycling & head bolt torquing it would be tough to get it "dead nuts" flat & level.
Posted By: Performance Only

Re: Q. for engine shop owners/employees, head flatness? - 04/18/12 11:14 PM

i mill heads every day, so all i can tell you is on a head that's not warped i set it up to be within .0001"-.0002" from end to end and front to back (X-Y). that might be closer than it needs to be, but when you can get it that close or closer, why not do it.
Posted By: Flite_727

Re: Q. for engine shop owners/employees, head flatness? - 04/19/12 01:35 AM

Okay, thanks. you did mean to type 4 decimal places, right?
Posted By: Performance Only

Re: Q. for engine shop owners/employees, head flatness? - 04/19/12 02:14 AM

yes, 4 decimal places.
Posted By: an8sec70cuda

Re: Q. for engine shop owners/employees, head flatness? - 04/19/12 01:26 PM

If it was less than .002" out of level, I normally wouldn't cut it. Any more and it normally got cut...or if I could see any imperfections on the deck surface. This is just what I did when I was doing machine work and never had any problems.
If I knew the head was run hot, it automatically got cut...unless the tolerance on the particular head was real close. Heads will warp in some strange ways when they get real hot.

A friend of mine (who is a real cheapskate) had me check his ZL1 BBC heads for him. One head was fine, the other was .008" out on the valley side of the deck. I told him it needed to be cut, but he said it'd be fine. Sure enough, he was right. He put em back on the 13.5:1 496" BBC and ran em for another year or so before switching to AFR heads. As far as I know, those heads are on a 427 now and running fine.
Posted By: Guitar Jones

Re: Q. for engine shop owners/employees, head flatness? - 04/19/12 06:48 PM

Most factory specs for aluminum heads are .002 or less. No reason that wouldn't work on a high performance engine either.
Posted By: Cab_Burge

Re: Q. for engine shop owners/employees, head flatness? - 04/19/12 07:10 PM

Quote:

Most factory specs for aluminum heads are .002 or less. No reason that wouldn't work on a high performance engine either.

A composition head gasket is a lot more forgiving than a steel shim head gasket is Flat, on cylinder heads and block deck surfaces, are good
Posted By: Performance Only

Re: Q. for engine shop owners/employees, head flatness? - 04/19/12 09:05 PM

Quote:

if you've got an alum. head that has never been warped due to overheating, & never been cut before, how flat & level does it need to be, before making a cut across the deck? i'm guessing due to normal circumstances such as thermal cycling & head bolt torquing it would be tough to get it "dead nuts" flat & level.



guys, i took this question as how close should the setup be before you actually cut. i was thinking of it like maybe he want's to mill the heads for higher compression .050" or something. that's what i was referring to in my last post.
if the question is how much twist or uneveness is acceptable, that's a whole different answer. .002 over the length of the head, regardless of material shouldn't be a problem.
we get heads in all the time where guys have cleaned them up with roloc discs and they have pockets where they might need .010 or more taken off just to get them close to straight again.
in any case, i do feel your setup prior to cutting should be as close as you can get it.
Posted By: Flite_727

Re: Q. for engine shop owners/employees, head flatness? - 04/19/12 10:34 PM

Quote:

Quote:

if you've got an alum. head that has never been warped due to overheating, & never been cut before, how flat & level does it need to be, before making a cut across the deck? i'm guessing due to normal circumstances such as thermal cycling & head bolt torquing it would be tough to get it "dead nuts" flat & level.



guys, i took this question as how close should the setup be before you actually cut. i was thinking of it like maybe he want's to mill the heads for higher compression .050" or something. that's what i was referring to in my last post.
if the question is how much twist or uneveness is acceptable, that's a whole different answer. .002 over the length of the head, regardless of material shouldn't be a problem.
we get heads in all the time where guys have cleaned them up with roloc discs and they have pockets where they might need .010 or more taken off just to get them close to straight again.
in any case, i do feel your setup prior to cutting should be as close as you can get it.



i was referring to how flat the head surface itself should be, once secured in the fixture, ready to cut. sorry for any confusion.
anyways i googled it & it appears .002" is the norm for alum. V8's the only reason i posted on moparts, is that i wanted input from some of the engine builders whose opinion i've come to value in the 13 or so yrs. i've been loitering here.
Posted By: an8sec70cuda

Re: Q. for engine shop owners/employees, head flatness? - 04/19/12 10:39 PM

Quote:

Quote:

Quote:

if you've got an alum. head that has never been warped due to overheating, & never been cut before, how flat & level does it need to be, before making a cut across the deck? i'm guessing due to normal circumstances such as thermal cycling & head bolt torquing it would be tough to get it "dead nuts" flat & level.



guys, i took this question as how close should the setup be before you actually cut. i was thinking of it like maybe he want's to mill the heads for higher compression .050" or something. that's what i was referring to in my last post.
if the question is how much twist or uneveness is acceptable, that's a whole different answer. .002 over the length of the head, regardless of material shouldn't be a problem.
we get heads in all the time where guys have cleaned them up with roloc discs and they have pockets where they might need .010 or more taken off just to get them close to straight again.
in any case, i do feel your setup prior to cutting should be as close as you can get it.



i was referring to how flat the head surface itself should be, once secured in the fixture, ready to cut. sorry for any confusion.
anyways i googled it & it appears .002" is the norm for alum. V8's the only reason i posted on moparts, is that i wanted input from some of the engine builders whose opinion i've come to value in the 13 or so yrs. i've been loitering here.


Gotcha...I misread your original question then. I used to shoot for .0005" end to end before I'd cut them.
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