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Old 09-08-2020, 08:34 AM   #1
patmanta
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Default EAB Heads & their Piston Reliefs - Is this right?

Years ago I bought a set of cleaned and machined EAB heads from a machine shop off of ePay. Well, I finally took them out and started scrutinizing them and I noticed something that struck me as very odd. The dome reliefs for the pistons are not uniform in size. Were these heads milled incorrectly?

Any help is appreciated. I am trying to build my engine this fall, Thanks!

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Old 09-08-2020, 09:02 AM   #2
51 MERC-CT
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

Should all be the same.
Stock dimension on NOS EAB head measures 2.975"
You will probably have to do an 'aluminum ball' check using the smallest dim. to check for clearance, if good, mill to match.
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Old 09-08-2020, 09:15 AM   #3
JSeery
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

Is this along one head or different measurements on two different heads? If it is left to right along one head it appears to be milled at an angle.
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Old 09-08-2020, 09:18 AM   #4
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

I looks like they get progressively larger front to back. I don't know what is involved with machining heads, but maybe they weren't held level and took more from the front.
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Old 09-08-2020, 11:46 AM   #5
tubman
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

I had to have one of the heads on my last build angle milled to make up for a bad previous decking the block had received. After a lot of measuring and checking, I determined that, although the deck was flat, it was .030" lower in the back than the front. I finally found a machinist who understood my problem and was able to mill the head a compensating amount. Decking the block was not an option because the short block was already assembled and the notorious thinness of flathead decks. If there is any interest, here's a link to a thread about it : https://www.fordbarn.com/forum/showthread.php?t=228269. Beware, it is three pages long and there were some disagreements.

While this may not be the case in your particular situation, it did end up with me having a head milled more on one end than on the othere, so it CAN happen.
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Old 09-08-2020, 11:55 AM   #6
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

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A lot of those type sellers don't care if they mill the same amount or not. I've seen it happen before. One head had been milled so far that it had material removed from the bottom of the thermostat pocket area (8BA heads).
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Old 09-08-2020, 12:02 PM   #7
patmanta
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Unhappy Re: EAB Heads & their Piston Reliefs - Is this right?

Quote:
Originally Posted by 51 MERC-CT View Post
Should all be the same.
Stock dimension on NOS EAB head measures 2.975"
You will probably have to do an 'aluminum ball' check using the smallest dim. to check for clearance, if good, mill to match.
THANKS! That measurement will definitely come in handy. And now I know they are indeed supposed to be uniform and I am not crazy.

Quote:
Originally Posted by JSeery View Post
Is this along one head or different measurements on two different heads? If it is left to right along one head it appears to be milled at an angle.
This is indeed one head and I was afraid that was the case.

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Originally Posted by 40cpe View Post
I looks like they get progressively larger front to back. I don't know what is involved with machining heads, but maybe they weren't held level and took more from the front.
Yes, this is looking to be the case.

Quote:
Originally Posted by tubman View Post
I had to have one of the heads on my last build angle milled to make up for a bad previous decking the block had received. After a lot of measuring and checking, I determined that, although the deck was flat, it was .030" lower in the back than the front. I finally found a machinist who understood my problem and was able to mill the head a compensating amount. Decking the block was not an option because the short block was already assembled and the notorious thinness of flathead decks. If there is any interest, here's a link to a thread about it : https://www.fordbarn.com/forum/showthread.php?t=228269. Beware, it is three pages long and there were some disagreements.

While this may not be the case in your particular situation, it did end up with me having a head milled more on one end than on the othere, so it CAN happen.
Yeah, it would seem someone either milled these wrong or milled them for someone who needed them cut at an angle. This is a real bummer for me because I do not have need of angle cut EAB heads so the money I spent on them is probably a loss now unless I have them cut level and have the domes and reliefs re-cut. It is probably cheaper and healthier to just have the rusty set of uncut heads I have in the shed cleaned up and put into service
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Old 09-08-2020, 12:11 PM   #8
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

If I understand your dimensions it is perfectly normal after truing a head to have the center domes larger. This is because the heads "warp" with the center lower than the ends when viewed with the gasket face up. The machinist probably leveled the head to the best possible condition and removed the minimum material which resulted in more surface thickness removed at each end.
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Old 09-08-2020, 12:12 PM   #9
patmanta
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

Quote:
Originally Posted by rotorwrench View Post
A lot of those type sellers don't care if they mill the same amount or not. I've seen it happen before. One head had been milled so far that it had material removed from the bottom of the thermostat pocket area (8BA heads).
I am really bummed out about this but I bought them 5 years ago on eBay and really should have asked more questions about what was done to them and looked closer. At the time it didn't even occur to me that these would have been milled improperly or for a specific block.
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Old 09-08-2020, 12:21 PM   #10
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

Before making any decisions might install the head on your block and check the clearances for each cylinder. If you are wanting to improve the compression you would end up milling the heads anyway. You are looking for around .050 clearance. Unless you are using a high lift cam, valve clearance shouldn't be an issue.
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Old 09-08-2020, 12:38 PM   #11
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

Agree with JSeery. Might not be a deal breaker.
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Old 09-08-2020, 01:15 PM   #12
patmanta
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

Quote:
Originally Posted by JSeery View Post
Before making any decisions might install the head on your block and check the clearances for each cylinder. If you are wanting to improve the compression you would end up milling the heads anyway. You are looking for around .050 clearance. Unless you are using a high lift cam, valve clearance shouldn't be an issue.
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Originally Posted by flatjack9 View Post
Agree with JSeery. Might not be a deal breaker.
I'll check them, or see what my machine shop thinks at least, but these are EAB heads so I'm expecting this to be a problem in the piston area and to need relieving in the valve area with the Max-1 cam I'm using. I haven't been able to get a coherent depth reading in the valve pockets due to the slanted milling as well as the very rough texturing in the chamber.
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Old 09-08-2020, 01:27 PM   #13
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

JJseery & Jack have it.
The EAB's on my big bad 286 were warped.....that's what those heads do. I did
some simple calculations and had the heads milled to my numbers. I ran 3 studs in each
bank and after blueing the domes and the valve heads I placed the head/s on the block .

With hand pressure on the head I spun the motor over then removed it. The
blueing told the story. Any areas of intereference showed up on the head as spots of blue. After about 6 or 8 hours of relieving per head all interference was gone. The

crushed thickness of a BEST head gasket is .040........and that is my clearance.
Don't be shocked if you see heavy piston to chamber contact at 3 o'clock on one bank and 9 o'clock on the other. Aluminum balls will never get you this close. Compression is the cheapest way to performance.
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Old 09-09-2020, 06:41 AM   #14
Frank Miller
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

Here is what i have been told about this. Heads are really not milled or surface ground but simplay placed on a big belt sander to get them flat. The leading edge of the belt can be more aggressive so the head needs to be rotated.
If the above head is flat you could probably cc the chambers and run them as is with no problems.

A machinist told me that ideally a head should be surface ground. I'm guessing to do that you would need to square the head to the grinder which I assume could be a bit of a chore as there is no flat area opposite to rest it against. When I think too much I wonder how half the stuff out there is running, including mine.
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Old 09-09-2020, 09:25 AM   #15
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Default Re: EAB Heads & their Piston Reliefs - Is this right?

Storing heads on their wood or metal shelf that's not flat for long periods of time can cause warping. I bolt them together and stor them on edge. With the cost og new alum heads going through the roof. Have them angle milled .070" This will bring an 8BA combustion chamber down to aprox 65.70 CC. check va;ve clearance and use a dremmel to add clearance. Stock cam should clear. I use alum balls to check pisyon to head clearance. I'll be doing this to a set of EAB heads in the near future for the 258 build.
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