Cylinder head milling

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Dan the man

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Been reading, reading. Anyway I came across some interesting articles on milling cylinder heads or the block deck surface and from what I've read that for every 0.010" removed that .0048" needs to be removed from the intake side of the cylinder head in order to maintain proper intake port alignment. The China wall was mentioned but I don't remember what was said. I don't know if any of this is fact, how much of this is true. One machine shop did say that if a total of 0.040" or more is milled that the intake side has to be done, again I'm not speaking from experience and I don't know this as fact.
 
Just use a thicker head gasket.

If it fits, it sits.

But there may be some logic to it. It's been awhile since I've read anything about cylinder head machining. I need to find my books of automotive knowledge.
 
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Yeah, sounds about right. It's just basic geometry. Usually if you're just doing a skim cut to true things up, it won't be needed; but it ultimately depends on how much gets taken off.
If you're cutting the heads to gain compression, then you're taking a bunch off and you definitely need to run the numbers. And recheck your pushrod length while you're at it.
If you throw thicker head gaskets on it, you just lose whatever compression you gained by milling.
 
Professor Fate said:
Yeah, sounds about right. It's just basic geometry. Usually if you're just doing a skim cut to true things up, it won't be needed; but it ultimately depends on how much gets taken off.
If you're cutting the heads to gain compression, then you're taking a bunch off and you definitely need to run the numbers. And recheck your pushrod length while you're at it.
If you throw thicker head gaskets on it, you just lose whatever compression you gained by milling.
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I agree with you.
 
Ant said:
Just use a thicker head gasket.

If it fits, it sits.

But there may be some logic to it. It's been awhile since I've read anything about cylinder head machining. I need to find my books of automotive knowledge.
Click to expand...
Most machine shops have a good idea on what works and what is needed. If they get this kind of stuff wrong, that will not look good for business.

I could not find the book I was looking for, but I got some information from two other books, but one tells you to machine the intake manifold.
I usually just trust the machine shop.

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Dan the man said:
Been reading, reading. Anyway I came across some interesting articles on milling cylinder heads or the block deck surface and from what I've read that for every 0.010" removed that .0048" needs to be removed from the intake side of the cylinder head in order to maintain proper intake port alignment. The China wall was mentioned but I don't remember what was said. I don't know if any of this is fact, how much of this is true. One machine shop did say that if a total of 0.040" or more is milled that the intake side has to be done, again I'm not speaking from experience and I don't know this as fact.
Click to expand...
Wrong, where did you read that? The correct relationship is for every .010 on the block face you need .0095 from the intake face of the head. So .040 means cut .038 from the intake face of the head to keep the same relationship for a head. I have never milled the china wall on the intake or block. You can guess or play games, I'm just not into that.
 
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This is a question only. So your saying that if the heads are milled 0.050" and the deck surface is milled 0.012" and a thinner head gasket is used that this doesn't affect port alignment at all?
 
66fs said:
I have never milled the china wall on the intake or block.
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Me neither- that's a big whompin' gap at the china wall/manifold that usually gets sealed by a cork or foam gasket, or a big fat old bead of RTV. Any shop that tells you that you need to mill one of those surfaces is just trying to make a couple extra bucks off of you. Does anybody seriously think a .028-.084 cut off the manifold bottom or the china wall amounts to a hill of beans when you've already got a quarter inch gap with a foam seal?
 
66fs said:
The correct relationship is for every .010 on the block face you need .0095 from the intake face of the head.
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Yes! My book is right thank god.

I love books with valuable knowledge that I can take anywhere without an internet or cellular connection. :)
 
Ant said:
Just use a thicker head gasket.

If it fits, it sits.

But there may be some logic to it. It's been awhile since I've read anything about cylinder head machining. I need to find my books of automotive knowledge.
Click to expand...

You’d need a THINNER gasket.
 
66fs said:
Wrong, where did you read that? The correct relationship is for every .010 on the block face you need .0095 from the intake face of the head. So .040 means cut .038 from the intake face of the head to keep the same relationship for a head. I have never milled the china wall on the intake or block. You can guess or play games, I'm just not into that.
Click to expand...
You are correct, I miss read the information
 
Professor Fate said:
Yeah, sounds about right. It's just basic geometry. Usually if you're just doing a skim cut to true things up, it won't be needed; but it ultimately depends on how much gets taken off.
If you're cutting the heads to gain compression, then you're taking a bunch off and you definitely need to run the numbers. And recheck your pushrod length while you're at it.
If you throw thicker head gaskets on it, you just lose whatever compression you gained by milling.
Click to expand...
Just get better pistons. Probably cheaper.
 
I had .060 taken off my heads and they cut the intake side but don't know how much. Didn't do anything to the block or intake and didn't have any problems.
 
Newbomb Turk said:
You’d need a THINNER gasket.
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What! If you are not looking to increase the compression but just want to keep everything lined up to the factory locations as close as possible, you need to use a THICKER head gasket.
 
Ant said:
What! If you are not looking to increase the compression but just want to keep everything lined up to the factory locations as close as possible, you need to use a THICKER head gasket.
Click to expand...

Yup...my bad. Head was inserted completely into my buttocks when I read your post.

My had is now fully remove from my buttocks and the removal went well.
 
Ant said:
Just use a thicker head gasket.

If it fits, it sits.

But there may be some logic to it. It's been awhile since I've read anything about cylinder head machining. I need to find my books of automotive knowledge.
Click to expand...
Depends on the why the block or head(s) are being milled. Could be warping and mill to get it flat again. If milling to zero deck or increase compression there is a good possibility more than a few thousandths is removed. An engine that has bbeen remanufactured a couple of times may have enough cut requiring milling the intake face of the intake and a different amount taken off the china wall portion of the manifold.
 
Dan the man said:
Been reading, reading. Anyway I came across some interesting articles on milling cylinder heads or the block deck surface and from what I've read that for every 0.010" removed that .0048" needs to be removed from the intake side of the cylinder head in order to maintain proper intake port alignment. The China wall was mentioned but I don't remember what was said. I don't know if any of this is fact, how much of this is true. One machine shop did say that if a total of 0.040" or more is milled that the intake side has to be done, again I'm not speaking from experience and I don't know this as fact.
Click to expand...
Where's my red x..
 
Professor Fate said:
Me neither- that's a big whompin' gap at the china wall/manifold that usually gets sealed by a cork or foam gasket, or a big fat old bead of RTV. Any shop that tells you that you need to mill one of those surfaces is just trying to make a couple extra bucks off of you. Does anybody seriously think a .028-.084 cut off the manifold bottom or the china wall amounts to a hill of beans when you've already got a quarter inch gap with a foam seal?
Click to expand...
I took .030 off my 273 heads. The intake was close to the China wall. A nice bead of black silicone did the trick.
 
i wouldn't go to far milling the open chamber X or J heads, i hear if you don't have at least .100 between the "quench" area and the piston if effects the flame travel..
 
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