Cylinder Head Gasket...

Discussion in 'Technical' started by Buck62, Jun 17, 2017.

  1. Buck62

    Buck62 Member

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    Right now I'm in the middle of lining up some performance mods to go on the 4.1L 250ci Automatic in my 1974 Mercury Comet. My eyes are on a re-manufactured early 80's cylinder head, as they have larger valves and more intake log cc's. Despite the fact that the engine in the Comet already runs well as it sits (it smokes the tires a bit too... stock ;)), the plan is to do the 2V conversion with an Autolite 2100 directly mounted, and possibly do a bit of porting.


    ----Here is my question----


    Because a new head is going on, I want a new gasket to replace the old one that's been sitting there for God knows how long. However, these older cars used thin steel shim gaskets, ranging anywhere from about .015" to .025" thick. Today, companies use these composite materials, which are great and all for a good seal, but they are usually double the thickness. This difference leads to a noticeable change in compression, and thus power output. I believe another thread (can't remember if it was on fordsix.com or this forum) put the difference at about .5 compression points per .020". That would be enough to make the mods mentioned above not worth it for the cash going into the project.

    I don't want to machine the head to compensate for the added thickness for cost, reliability, and time reasons, but I want to maintain what stock compression the car came with, 8.0:1 for 1974.

    To do this, I would need to find one of these steel shim gaskets. Problem is that I can't seem to find these things anywhere, and I just run into another composite gasket.

    If anyone has any idea as to where I could find the gasket, could you post a link so I can buy one?

    Thanks in advance!
     
  2. Powerband

    Powerband Member

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    ---- 1976 Comet --- 1974 Maverick- - '61 Comet T'Bolt Six ---- 'quite a few projects ...
    ... all 144, 170, 200 & 250ci engines came from the factory with steel shim head gaskets that have a compressed thickness of approximately .025", however these gaskets are no longer available and scarce as NOS (New Old Stock). As such, you'll need to use an aftermarket head gasket (produced by Felpro, Victor, Corteco, etc) which are composite type head gaskets that have compress thickness ranging from .040" to .055", depending on the manufacturer. Composite gaskets seal better and last longer than OEM steel shim gaskets, but to use them you'll need to mill the head to compensate for the difference in gasket thickness. To do that you need to compare the thickness of the OEM gasket that was removed, to the composite gaskets advertised compressed thickness, then mill the head accordingly. For example, if your old shim gasket had a compressed thickness of .025", and the new gasket has a compressed thickness of .050", you'll need to mill .025" off the cylinder head to maintain the same CR, more if you want to increase the C/R.


    You will see small block six head gaskets sold as fitting 144, 170, 200 and 250 cid sixes. The 144 and 170's have a cylinder bore of 3.5" and 200 and 250's haev a 3.68" bore. They are not interchangeable.

    Steel shim gaskets for the 3.5" bore 170's are available from a few vendors and other sources BUT no source of the 3.68 bore 200/250 steel shim gaskets are readily available. I have considered re-using steel gaskets I've removed from a 200 and 250's.

    Simplest ( only? ) solution is to mill the head to maintain the CR. I strongly recommend first measuring the combustion chamber volume to verify your initial projected CR or you will be guessing at multiple factors in your determination.

    [​IMG]


    [​IMG]

    https://egge.com/


    have fun
     
  3. greasemonkey

    greasemonkey Burnin corn

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    Could a steel gasket be reused if coated with a sealant like the old Indian head stuff? I'm surprised someone doesn't make a mls gasket.
     
  4. Buck62

    Buck62 Member

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  5. rthomas771

    rthomas771 Member Supporting Member

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    Do you know the price of this custom made head gasket? Might be cheaper to have your head shaved.
     
  6. Buck62

    Buck62 Member

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    $41.99 for the gasket.

    What's the average price of milling the head?
     
  7. 71gold

    71gold Frank Cooper Supporting Member

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  8. duramax59

    duramax59 Member

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    I maybe mistaken but I believe these are steel shims and not head gaskets. They are used to correct deck height. Just my 2 cents worth.
     

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