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Milling 239 Y-block heads QUESTION....

Posted By 82warren 4 Years Ago
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82warren
Posted 4 Years Ago
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Hey guys... I'm rebuilding a 239Y right now, I have the heads off, everything is marked EBU.
How much can be milled off these heads ..?..   Or, what do you guys recommend ??
I drive my '54 a lot and far sometimes, I love the great gas mileage of the 239 and want to stick with it.
I'll follow your expert advice, no arguments !!    :-))
Thanks much,
82warrenhttp://forums.y-blocksforever.com/uploads/images/2bd5358b-4a6e-4f87-9bff-be66.jpg

Ted
Posted 4 Years Ago
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Warren.  I don’t see an answer to your question and after looking up the amount to mill in the 1955 Service Manual, I don’t find a definitive answer there either.  In the ’57 manual, head milling is limited to 0.010” and most of us will go with as much as 0.025” of mill on the ’57 unposted ‘G’ heads.  The posted ‘G’ heads I’ve taken as much as 0.065” and I’ve seen as much as 0.080” on the posted 113 heads without any head gasket sealing issues.
 
With all that being said, I would treat the 1954 heads like any ’55 head in that I’ll hold head milling to a 0.050” max number.  The ’55 heads are designed somewhat differently than the highly touted ‘unposted’ G heads so the ’54 heads can likely be treated the same as the ’55 heads.  The 1955 272 "182HP Special" heads were factory milled 0.030" so that should represent a very safe number.  I would suggest checking the combustion chamber volumes on both of your heads and then mill both heads accordingly so that they are both equal in cc’s.  Give a shout if you need some help with the number crunching on that.

Lorena, Texas (South of Waco)


patm
Posted 4 Years Ago
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This has been my experience.

I also have a 1954 with a 239, all EBU with a 13 tooth distributor gear. I rebuilt the engine with the steel shim head gaskets, but there was seepage between the block and the heads (at that time, the machine shop said that head and block flatness was within specification and did not require milling or decking).

I replaced the head gaskets with BEST composition head gaskets. My thought was to compensate for the gasket's thickness and maybe add a little compression. I had the heads milled .040. Intake bolted perfectly and all is well for 2 plus years

Pat in Arizona.
Joe-JDC
Posted 4 Years Ago
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While not Y-block specific, many of Ford's iron heads were cast with a nominal .350" thick fire deck, especially on those engines that were higher compression from the factory.  They did this to keep the combustion chambers from collapsing under compression, and many racers over time found that most iron heads could sustain street compression with the fire deck at .250" or more.  Once a head was cut more than .100", they would collapse and crack with 12:1 or higher compression.  I have found this in my porting over the years when the heads had been milled too much.  If you can get a micrometer in a clean spot, measure the deck thickness, and that will give you an idea just how much has been milled, or can be milled.  The problem you may run in to is that rust from years of neglect or non anti-freeze usage may have eroded the water passages and the thickness may be much less than when new.   Joe-JDC

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82warren
Posted 4 Years Ago
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Hi Ted,
Yea', I've done some digging also and was told that you can mill off .060 no problem but ... if you go much over .030 then there is a problem with the intake manifold holes being in line with the head openings.  I can see where that could be a problem but ...  I also think if that alignment is a little too far out of whack then you could cut away some cast iron on both manifold and head to at least breath OK, might have to cut a little of the gasket away to match this, I doubt it would hurt anything.  The main thing is to come up with more HP because my car is using a 3:54 rear end with overdrive and that gears us up a fair amount.   I could have opted for a 312 but ....  this would raise cain with my gas mileage, the 239 can't be beat in that respect, our last long trip gave up over 20 mpg and this is a big full size fordor Crestline with a C-kit on the back as well.  The car is completely original and 6v, a nice 8 tube radio as well.
We're planning a LONG trip out west this summer, with luck we'll have this baby running like a song. 
Thanks a lot, we'll stay posted,
Warren, in MN






Ted
Posted 4 Years Ago
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The rule of thumb is 0.014” off the intake gasket surface for each 0.010” milled from the heads and/or deck.  The caveat to switching to composite head gaskets is you can mill 0.025” from the heads and/or deck which gets the intake back to its original height.  And then there is typically 0.025” additional that can be milled from the decks and/or heads before the intake fit itself becomes a problem.  That means if switching from a steel shim head gasket to composite, you can mill a total of 0.050” from the decks and heads before becoming concerned about the intake manifold fit.  After that point, then start milling 0.014” from the intake side of the head for each additional 0.010” taken from the heads and/or deck.  I do prefer milling the intake side of the head rather than the intake manifold itself simply due to trying to keep the intake manifold where it’s not specific to a particular engine combination.

Lorena, Texas (South of Waco)


82warren
Posted 3 Years Ago
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Thanks Ted, now I know how much I can mill, very good to know.
30 coupe
Posted 3 Years Ago
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Ted, could you tell me how to Identify the '55  272  182 HP  "special" heads?   thank you,-----Jim
Ted
Posted 3 Years Ago
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30 coupe (2/24/2016)
Ted, could you tell me how to Identify the '55  272  182 HP  "special" heads?   thank you,-----Jim

The early 1955 182HP heads had casting numbers ECL-B and ECG-A for the later units.  These part number will be found in the valve train area of the heads.  There was a head cracking problem on the early heads which was corrected by bringing out the ECG-A head.  At the tailend of the 1955 model run, the 182HP heads had a casting number ECG-C which was located on the exhaust side of the heads.  By measuring the two center outside pads, the 182HP heads will have a factory measurement of 0.964-0.966” whereas the Thunderbird 292 heads with the same casting numbers will have a pad measurement of 0.999-1.001”.



Lorena, Texas (South of Waco)


30 coupe
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Ted, I have a set of those ECG-C heads are they "desirable" ? or valuable ?   I am  just curious.   Thanks----Jim 


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