The Ford Barn

SoCalCoupe · 01-21-2023, 02:21 PM

Bought a cylinder head with a known flaw thinking it could be fixed. It had a tiny hole in the combustion chamber. Found an expert aluminum welder. Said he'd have to grind it out first then weld fill it to do it right. When he ground it out, he found the tip of a carbide drill bit at the bottom.

Go figure. I can't imagine how anyone could do that to a cylinder head by accident. Guy in my car club speculated that it was done intentionally by the manufacturer to prevent selling it due to some other flaw. Can't detect any other flaw though.

Now I have this blob of weld, as expected, rather than a hole in the head. Seems the head should be milled to make the mating surface perfectly flat (been advised no more than 0.005") and that inside of the combustion chamber should be smoothed out and matched with a handheld rotary porting tool like a Dremel tool.

Sound good? Which should come first, the milling or the hand-held touch-up? I'm thinking the hand-held touch-up.

tubman · 01-21-2023, 02:40 PM

Did you remove the drill bit chunk?

SoCalCoupe · 01-21-2023, 02:47 PM

Quote:

Originally Posted by tubman

Did you remove the drill bit chunk?

Yes, the drill bit chunk was removed.

tubman · 01-21-2023, 02:58 PM

Quote:

Originally Posted by SoCalCoupe

Yes, the drill bit chunk was removed.

That's what I thought, but I just wanted to make sure.

It looks like you're good to go. I'd let my machinist (the guy with the mill) decide how and what to do.

tom1948 · 01-21-2023, 02:41 PM

My opinion. I would mill it a little high(.02-.05) and then finish it by hand. By that I mean; using a straight edge with 320 and finish it with 800 to 1000 grit. with the dremel you might get little gouge that can't be seen until you put it under pressure. Just my 2 cents. alternative method: flat steel surface and valve grinding compound. I used this on aluminum heads when I worked on imports. tom

Karl Wolf · 01-23-2023, 02:52 PM

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If you mill the head, the amount taken off is determined by how out of flat the head is,
and the set up in the machine. If the warp is .020, You can't just take off .005.

I would start by using a sharp, possibly new aluminum file.
If you put tape on the file, leaving the center open,
so that the weld is the only thing cut, you can avoid making
new scratches in the surface of the rest of the head.
The weld area is likely to have some pits that won't be practical to machine out.
There might be some filler product that may help.

Karl

alchemy · 01-23-2023, 07:20 PM

95 percent of the weld blob is in the dome. I'd carefully take a grinder to that area. Then, a fine file to smooth the blob off the sealing surface. Then have the head checked for flatness. You may get lucky and it didn't warp any.

SoCalCoupe · 01-23-2023, 10:32 PM

Quote:

Originally Posted by Karl Wolf

I would start by using a sharp, possibly new aluminum file. If you put tape on the file, leaving the center open, so that the weld is the only thing cut, you can avoid making new scratches in the surface of the rest of the head. The weld area is likely to have some pits that won't be practical to machine out. There might be some filler product that may help.

Karl

Quote:

Originally Posted by alchemy

95 percent of the weld blob is in the dome. I'd carefully take a grinder to that area. Then, a fine file to smooth the blob off the sealing surface. Then have the head checked for flatness. You may get lucky and it didn't warp any.

Thanks for the ideas. I have a recommendation for a local machinist that can mill a flathead head but haven't been able to reach him; he's semi-retired and makes himself scarce.

That may drive me to the do-it-yourself solution. I could PROBABLY do it with a file and Dremel tool, but not having done any head work or block work before have very low confidence.

Brad

Mart · 01-24-2023, 05:16 AM

I'd just carefully grind and file by hand. Lay a gasket on it and see if the blob is on the fire ring part of the gasket. The dome is in mid air and not a critical mating surface. Once the dome is licked out with a grinder (dremel type) there will not be much left on the surface and it can be removed by careful sanding.

I wouldn't have it milled.

01-21-2023, 02:21 PM	#1
SoCalCoupe Senior Member Join Date: Sep 2021 Location: Point Loma, San Diego, CA Posts: 529	How to fix my aluminum cylinder head? Bought a cylinder head with a known flaw thinking it could be fixed. It had a tiny hole in the combustion chamber. Found an expert aluminum welder. Said he'd have to grind it out first then weld fill it to do it right. When he ground it out, he found the tip of a carbide drill bit at the bottom. Go figure. I can't imagine how anyone could do that to a cylinder head by accident. Guy in my car club speculated that it was done intentionally by the manufacturer to prevent selling it due to some other flaw. Can't detect any other flaw though. Now I have this blob of weld, as expected, rather than a hole in the head. Seems the head should be milled to make the mating surface perfectly flat (been advised no more than 0.005") and that inside of the combustion chamber should be smoothed out and matched with a handheld rotary porting tool like a Dremel tool. Sound good? Which should come first, the milling or the hand-held touch-up? I'm thinking the hand-held touch-up.

01-21-2023, 02:40 PM	#2
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 11,639	Re: How to fix my aluminum cylinder head? Did you remove the drill bit chunk?

01-21-2023, 02:41 PM	#5
tom1948 Senior Member Join Date: Aug 2014 Location: west palm beach florida Posts: 254	Re: How to fix my aluminum cylinder head? My opinion. I would mill it a little high(.02-.05) and then finish it by hand. By that I mean; using a straight edge with 320 and finish it with 800 to 1000 grit. with the dremel you might get little gouge that can't be seen until you put it under pressure. Just my 2 cents. alternative method: flat steel surface and valve grinding compound. I used this on aluminum heads when I worked on imports. tom

01-23-2023, 02:52 PM	#6
Karl Wolf Senior Member Join Date: May 2010 Location: Mill Valley,Ca. Posts: 1,539	Re: How to fix my aluminum cylinder head? Sponsored Links (Register now to hide all advertisements) If you mill the head, the amount taken off is determined by how out of flat the head is, and the set up in the machine. If the warp is .020, You can't just take off .005. I would start by using a sharp, possibly new aluminum file. If you put tape on the file, leaving the center open, so that the weld is the only thing cut, you can avoid making new scratches in the surface of the rest of the head. The weld area is likely to have some pits that won't be practical to machine out. There might be some filler product that may help. Karl

01-23-2023, 07:20 PM	#7
alchemy Senior Member Join Date: May 2010 Location: middle of Iowa Posts: 890	Re: How to fix my aluminum cylinder head? 95 percent of the weld blob is in the dome. I'd carefully take a grinder to that area. Then, a fine file to smooth the blob off the sealing surface. Then have the head checked for flatness. You may get lucky and it didn't warp any.

01-24-2023, 05:16 AM	#9
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 9,088	Re: How to fix my aluminum cylinder head? I'd just carefully grind and file by hand. Lay a gasket on it and see if the blob is on the fire ring part of the gasket. The dome is in mid air and not a critical mating surface. Once the dome is licked out with a grinder (dremel type) there will not be much left on the surface and it can be removed by careful sanding. I wouldn't have it milled.