The Ford Barn

1965 Mustang · 07-07-2025, 10:02 PM

I have to replace the cracked head on my 29 A. Going by the serial number my Car has a 1929 engine block in it. I got a used replacement head and noticed that the water passage openings in the new head and the cracked head I am replacing are slightly different. Most notably the replacement head is missing a round opening about 1 inch in diameter right in the middle of the space between cylinders 2 and 3. I have attempted to attach a photo of the 2 heads side by side. Does this difference matter? Why do 2 seemingly identical heads have slightly different openings for water passage. Thanks

JayJay · 07-07-2025, 10:43 PM

The oblong center cooling water hole was added in September 1929, so your new head may be earlier than that. It is also possible that the new head you have is one of a number of aftermarket clones that were produced. See https://www.fordgarage.com/pages/ABc...comparison.htm for some additional discussion.

It’s also possible that the original head you took off was not the original head, regardless of the engine. Over the years there have been many swaps of engines and components.

alexiskai · 07-08-2025, 12:22 AM

That hole is so interesting. The corresponding hole on the engine block side was originally round, and then it was elongated in March of '28. But apparently there was no hole at all on the cylinder heads until late '29, when it was added "to improve circulation." And of course the Burtz cylinder heads, as well as other aftermarket heads over the last century, remove the hole again... to improve circulation!

I used to think the documentation was ambiguous, and possibly the early heads had a round hole that matched the early engine blocks. But in the Indianapolis Service Letters, they write "An elongated hole is being added between combustion chamber in 2nd and 3rd cylinders, also corresponding holes in A-6051 cylinder head gasket... in addition to adding a hole in the cylinder head gasket, this gasket has been increased in thickness from .057-.069" to .067-.077"" (emphasis added).

JayJay · 07-08-2025, 09:21 AM

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Regardless, I suggest that you take your (new) head to an automotive machine shop and have it decked flat before you install it. No point in starting out with anything less than ideal to avoid leaks.

Regarding that hole, Vince Falter surmises that maybe it was added to help with casting mold stability, not just cooling. And Terry Burtz removed it to force more cooling water to the rear, where it runs hotter.

07-07-2025, 10:43 PM	#2
JayJay Senior Member Join Date: Jan 2020 Location: SF Bay Area Posts: 2,104	Re: Cylinder Heads The oblong center cooling water hole was added in September 1929, so your new head may be earlier than that. It is also possible that the new head you have is one of a number of aftermarket clones that were produced. See https://www.fordgarage.com/pages/ABc...comparison.htm for some additional discussion. It’s also possible that the original head you took off was not the original head, regardless of the engine. Over the years there have been many swaps of engines and components. __________________ JayJay San Francisco Bay Area ------------------------ 1930 Murray Town Sedan 1931 Briggs S/W Town Sedan It isn't a defect, it's a feature!

07-08-2025, 12:22 AM	#3
alexiskai Senior Member Join Date: Apr 2018 Location: Mebane NC Posts: 2,848	Re: Cylinder Heads That hole is so interesting. The corresponding hole on the engine block side was originally round, and then it was elongated in March of '28. But apparently there was no hole at all on the cylinder heads until late '29, when it was added "to improve circulation." And of course the Burtz cylinder heads, as well as other aftermarket heads over the last century, remove the hole again... to improve circulation! I used to think the documentation was ambiguous, and possibly the early heads had a round hole that matched the early engine blocks. But in the Indianapolis Service Letters, they write "An elongated hole is being added between combustion chamber in 2nd and 3rd cylinders, also corresponding holes in A-6051 cylinder head gasket... in addition to adding a hole in the cylinder head gasket, this gasket has been increased in thickness from .057-.069" to .067-.077"" (emphasis added). Last edited by alexiskai; 07-08-2025 at 12:28 AM.

07-08-2025, 09:21 AM	#4
JayJay Senior Member Join Date: Jan 2020 Location: SF Bay Area Posts: 2,104	Re: Cylinder Heads Sponsored Links (Register now to hide all advertisements) Regardless, I suggest that you take your (new) head to an automotive machine shop and have it decked flat before you install it. No point in starting out with anything less than ideal to avoid leaks. Regarding that hole, Vince Falter surmises that maybe it was added to help with casting mold stability, not just cooling. And Terry Burtz removed it to force more cooling water to the rear, where it runs hotter. __________________ JayJay San Francisco Bay Area ------------------------ 1930 Murray Town Sedan 1931 Briggs S/W Town Sedan It isn't a defect, it's a feature!