Two Different Heads

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srrodder

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Location
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My Car
1969 GT fastback restored
1971 Mach 1 original
I recently initiated a thread regarding Ignition Timing Settings and received a number of great posts in reply. Today I took a close look at the markings on the heads of my 1971 M code engine and find that apparently one is an open chamber 4V head and the other is a closed chamber 4V head. This is indicated by a 4 with a raised dome next to the 4 for the open chamber head and by a 4 and no dome for the closed chamber head – at least that is what I found for the meaning in researching the markings. So I guess sometime in the past an owner had to replace a head. I bought the Mustang 2 years ago, and I guess I should have done some more research and inspection of the car. I also guess I am in the market for a closed chamber 4V head.

I would appreciate it if anyone can verify the meaning of the markings and offer an opinion on how the two different heads would affect the running of the engine.

 
The *4 heads are not necessarily open chambered but they may have a slightly larger (up to 3 cc's) chamber....my guess...and it's just a guess...is that you have one D0AE-N head and one D1AE-GA head. No biggie to have that mixture.

To know for sure what you have, you need the casting number and the date code. You have to pull the intake and use a mirror to get the casting number...the date code is under the valve cover. Date code is likely sufficient to say whether it's close or open chamber.

 
Last edited by a moderator:
I recently initiated a thread regarding Ignition Timing Settings and received a number of great posts in reply. Today I took a close look at the markings on the heads of my 1971 M code engine and find that apparently one is an open chamber 4V head and the other is a closed chamber 4V head. This is indicated by a 4 with a raised dome next to the 4 for the open chamber head and by a 4 and no dome for the closed chamber head – at least that is what I found for the meaning in researching the markings. So I guess sometime in the past an owner had to replace a head. I bought the Mustang 2 years ago, and I guess I should have done some more research and inspection of the car. I also guess I am in the market for a closed chamber 4V head.

I would appreciate it if anyone can verify the meaning of the markings and offer an opinion on how the two different heads would affect the running of the engine.
Click to expand...
IMHO there is no correlation between dot vs no dot heads and chamber type.

 
I recently initiated a thread regarding Ignition Timing Settings and received a number of great posts in reply. Today I took a close look at the markings on the heads of my 1971 M code engine and find that apparently one is an open chamber 4V head and the other is a closed chamber 4V head. This is indicated by a 4 with a raised dome next to the 4 for the open chamber head and by a 4 and no dome for the closed chamber head – at least that is what I found for the meaning in researching the markings. So I guess sometime in the past an owner had to replace a head. I bought the Mustang 2 years ago, and I guess I should have done some more research and inspection of the car. I also guess I am in the market for a closed chamber 4V head.

I would appreciate it if anyone can verify the meaning of the markings and offer an opinion on how the two different heads would affect the running of the engine.
Click to expand...
I could well be wrong, but my understanding is that the 4 without the dot is a 70 N head @ 62.8cc closed chambers and the 4* is a 71 GA head with 64cc closed chambers. It was my understanding that the open chamber heads have the 4 or 4*, or 2 for 2 barrel, but it's the date codes that tell the story. I think that open chamber heads started around May of 71 for the "Q" code engine, but I cold be wrong on that too.

EDIT: I just looked at my list of heads and the 4 V open chamber ones had D1ZE-DA, D3ZE-AA or D2ZE-A which was the HO. These had 74-77cc chambers.

On the 70-71 4V heads, there could also have been a D0AE-G, H, M, N, and R (62.8cc) as well as D1AE-GA (64cc ). Finding casting numbers is a pain, but date codes should get you close.

 
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Thanks for the info - I'll at least take a look at the date codes. It will be a few days and maybe a week before I can get to this, so a reply post may be a little late.

 
To wrap this up, I tracked down and talked to the engine rebuilder. He said the heads were the same and were closed chamber heads. I found on another thread that a 4* head would be an open chamber head if cast beginning in January 1971. Since my Mach 1 was assembled in October 1970 it couldn't have a 2V head unless it had been replaced. :)

 
I meant to say 4V open chamber heads not 2V heads.

 
I meant to say 4V open chamber heads not 2V heads.
Click to expand...
I'd still pull the valve covers and take a look at the date codes. I don't know exactly when Ford started production on 4V open chamber heads for the Q code engines, but I do believe that the Q code was not introduced until about June of 71. My buddy has an M code and it was built at the end of April 71. Ford would likely have had some stock of 4V cc heads to use up though.

 TIP: replace the v/c gaskets with rubber ones so if and when you take the covers off again, it won't F up your gaskets.

 
Last edited by a moderator:

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