"915" RE-SURFACE QUESTION

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CFD244

CFD244

"I LOST MY ID IN A FLOOD"
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Hi Folks

Could i get a consensus from experience how much re-surfacing a head can take before the intake needs to be "worked"? Looking at a fresh set of O castings that have been re-surfaced. The combustion chambers were cc'd at 69. Thanks for the help.

2007.JPG
 
The 2 machine shops I use both are up to 0.020” ....intake angle is fine. At 0.040” the intake angles need to be adjusted. I’m no machinist but I did a 318 and had the stock heads cut 0.040” so I could use a felpro blue head gasket and not loose compression and my intake leaked at the bottom of the ports sucking oil from the valley on hard pulls.
 
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Why mess around. Those heads were probably milled .030. Cut the intake sides .0285 and forget about it. Now is the time.
 
Seller advises just a minimum off the face to clean up. Seller seems to be a decent guy. He had the heads done for himself but the block turned out to be cracked.
 
I generally find that about .030" is the limit. But even then while the intake will bolt on, the port will be misaligned. So it's really best to mill the intake or intake face of the heads as well.
 
I like what rusty says but do us all a favor if you cut the intake- stamp it underneath so if you ever sell it the new buyer does not get an issue they can’t chase down.
 
RustyRatRod said:
I generally find that about .030" is the limit. But even then while the intake will bolt on, the port will be misaligned. So it's really best to mill the intake or intake face of the heads as well.
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It really doesn’t matter, but I always do the intake manifold, as they are much cheaper to replace than the heads.

And, whichever one you decide to mill will only fit that block and intake combo. That’s the big squeal about machining the intake. Then it only fits “that” block, but if you machine the heads they only fit “that” block, unless the deck height is the exact same on the next block and the it take manifold is the exact same width.

You can measure 10 of the same intake manifolds and not one will be the same. Same thing with the heads. They only machine enough off the surface to get it clean and straight. They don’t machine to a number, except for the minimum. If it’s about the minimum and cleans up they send it.

That’s why all this only mill the heads so any intake will fit is just crazy. Ain’t none of this production junk machined to a spec.

That’s why I never mill a head, unless you need to reduce port volume door a Stock or Super Stock deal, and I ain’t smart enough to build that stuff.
 
If you have a .039-.046 thick felpro 1008 or 8553PT replacement head gaskets..you are only changing the head/port height .020 by milling .040 because the thicker gasket compensates.


Stock .019-.021 gasket

Aftermarket .039 , .046, .054
Thats a 1008, 8553pt and 519sd felpro gasket choice.

Now at 69cc they have been milled about .015 already '.0048 per cc for 340/360 open chamber'. So another .025 shouldn't cause any fitment issue.
The variable is the aftermarket intake manifold. They sometimes need cutting to fit. There are thin to thick intake gaskets available from felpro ranging from .035-.060 or so. Other brands have various thicknesses as well. You can permatack and add stack 'paper' composite gaskets but i wouldn't advise stacking a metal core style like the blue .035 felpros
 
Syleng1 said:
The 2 machine shops I use both are up to 0.020” ....intake angle is fine. At 0.040” the intake angles need to be adjusted. I’m no machinist but I did a 318 and had the stock heads cut 0.040” so I could use a felpro blue head gasket and not loose compression and my intake leaked at the bottom of the ports sucking oil from the valley on hard pulls.
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That's a machining screw up.
Geometry goof. They are supposed to be a mating angles... so that even you milled the heads intake or head surface... the only thing that can change is sitting high or low in relation to each other.
So.. they must have milled at the wrong angle. The cuttter took more off toward the manifold/valley side of the heads deck.

Any careful machinist will always do a scratch test by spinning the head by hand and moving the head across the deck lowering it just enough to make a scratch.. in which you can by eye easily see whether the scratch is the same width on each side and each end. Takes 2 min after fixing the head to the jig plate.


@CFD244 Fwiw i took .045 off my j head bringing them to 60cc. They were the same 69cc as yours . I was given the heads after some previous work and hard seats had been done 10 or so yrs earlier. I also took .012 off the block deck... so I did end up Milling the intake face of the heads as well .030 but not before I also had to measure the ld340 intake manifold I was using to find out it was tapered end to end and needed about .015 off of it to be straight.

I had a stacking of tolerances.
Consider your stacking of tolerances..because they add up together.

Do a gasket test fit, heads and intake on the block with gaskets.
 
Hi Folks

I tried to PM Moparofficial, and found an x by his name, and a status saying "left conversation permanently". Does this mean he has blocked me, or that he doesn't take pm's? Got the message right after I typed it? I don't understand?

Thanks
 
CFD244 said:
Hi Folks

I tried to PM Moparofficial, and found an x by his name, and a status saying "left conversation permanently". Does this mean he has blocked me, or that he doesn't take pm's? Got the message right after I typed it? I don't understand?

Thanks
Click to expand...

I think Justin has left that thread. Probably to escape the BS and varying opinions of trying to figure how much to mill the intake side when you don't know how much the block side was milled. My educated guess was for unmilled heads, and a good valve job and your stated chamber cc, since I cc'd more than a few J heads in my day.
 
CFD244 said:
Hi Folks

I tried to PM Moparofficial, and found an x by his name, and a status saying "left conversation permanently". Does this mean he has blocked me, or that he doesn't take pm's? Got the message right after I typed it? I don't understand?

Thanks
Click to expand...
Pm me.
 
66fs said:
I think Justin has left that thread. Probably to escape the BS and varying opinions of trying to figure how much to mill the intake side when you don't know how much the block side was milled. My educated guess was for unmilled heads, and a good valve job and your stated chamber cc, since I cc'd more than a few J heads in my day.
Click to expand...

Which is exactly why I say something once......maybe twice and move on. lol
 
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