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Subject: 8n Head specs

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IceChickenx    Posted 03-07-2022 at 09:23:36 [URL] [DELETE]        [Reply] [Email]  
  • 8n Head specs
  • Good Morning folks! Its been a while since I've posted a question. Story first:

    '48 (late '47) 8N. I'm pretty sure my head gasket has failed. I've searched and performed all the suggestions to reach this conclusion.

    Last time I did a cylinder head gasket was 20 years ago. Back then I had the head checked and decked (I don't remember the amount).

    Questions:
    1) What is the minimum height for the head? Meaning, there are only so many times you can deck the head before interference, right?
    2) Metal or soft head gasket?
    3) Do I use copper coat?
    4) Is it necessary for the head to be cleaned? Or can I put it right back on?
    5) Are the cap screws reusable?
    6) Any other questions I should be asking, but have failed to mention?

    I would hate to get rid of it. The date casting says it late '47.

    I appreciate any help.

    Thanks!
    Icechickenx

    Mike Maiman    Posted 03-08-2022 at 10:47:28 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n Head specs
  • Icechickenx,
    I'm currently rebuilding my '51 8N engine and I'm following John Korschot's tutorials "Overhauling the Engine" in How-To's. In part 3 John does a nice job of explaining the piston to head clearance issue which might be of help.

    I've also searched the web for rebuilding Ford flathead engines and found a great deal of info. One thing suggested (which I'm doing) is to replace the head bolts with threaded studs. Reason being the threads in 70+ year old blocks could be weak and not torque to proper specs. I found Dorman p/n 675-108 threaded studs on Amazon for $21.00 for a pk of 10. I had to buy 2 packs and also grade 8 - 7/16-20 nuts.

    Hope this helps.

    Pops    Posted 03-07-2022 at 17:38:27 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n Head specs
  • Icechickenx,

    1. The minimum height for the head is when the pistons start bumping it. Some pistons are higher than others. Is your engine head warped? If not, don't shave it. If you do shave it, test for piston bump afterwards by sitting the head on the engine without a head gasket and turning the engine over slowly. If the pistons bump, you'll have to either get a new head or grind some metal off the existing one.
    2. I've had better luck with metal head gaskets.
    3. Use copper coat on both sides of the gasket.
    4. Clean the head using an engine cleaner or degreaser.
    5. Are "cap screws" another name for "head bolts"? If so, they can be re-used, but you'll have more accurate torque readings with new bolts. Put a dab of sealant on the threads.

    Good luck!

    IceChickenx    Posted 03-13-2022 at 20:05:34 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n Head specs
  • Pops,
    What sealant do you recommend for the threads?
    Thanks!
    IceChickenx

    Pops    Posted 03-14-2022 at 09:44:31 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n Head specs
  • Permatex Aviation Form-A-Gasket #3

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