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Subject: Head Bolts/Studs

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Al    Posted 04-26-2022 at 11:34:38 [URL] [DELETE]        [Reply] [No Email]  
  • Head Bolts/Studs
  • It seems I have more questions each time I work on this tractor. I am working on the cylinder head and am having trouble deciding between bolts and studs. The Ford Dealer said that of the N tractors use head bolts. But online sources indicate the use of studs or a combination of the two. Any thoughts on this problem?

    Steve Dabrowski    Posted 04-26-2022 at 17:15:50 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Head Bolts/Studs
  • My 1947 vintage 8N had (and still has) studs. I removed them and shaved the top of the block when rebuilding the engine. Then I re-installed them after carefully cleaning the studs and threads in the head using plumbing tube wire brushes in my drill. I used aircraft gasket cement on the threads and torqued the studs to 10 ft-lbs in the block (want to be careful torquing too tight as you can cause a crack in the block with the shoulder of the stud).
    I read that the threads on Ford studs of the time were rolled and should not be chased using a tap or die which may cause them to leak. Using new bolts in a block originally made for studs could also cause leakage if not sealed using a good product.

    When tightening I fully warmed the engine and after allowing to cool repeated torquing until all of the nuts were fully tight at the specified level, it took five cycles of this on my 8N. Have had no leakage over the past five years since the rebuild and it continues to start on the first one or two cranks.

    TheOldHokie    Posted 04-27-2022 at 11:20:15 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Head Bolts/Studs
  • I knew I was out on a flimsy limb with the chronology of the changeover - should have checked before typing.

    Here is some manufacturing minutia for you Steve. Just about every mass produced externally threaded fastener made today (and for many decades past) has rolled threads. Its faster to produce and and it cold works the steel which relieves internal stress and makes the fastener a tiny bit stronger. Rolled or machined the thread fit tolerance is the same - for most commercial fasteners that is class 2A fit. Thread chasers as opposed to taps and dies are forming rather than cutting tools for the express purpose of not changing the thread fit.

    TOH

    Steve Dabrowski    Posted 04-27-2022 at 14:58:31 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Head Bolts/Studs
  • I'm not sure about the changeover, but guessed it coincided with the side mounted distributor. My concern on threads is using a tap as a chaser in the block where studs were used and causing a possible leak potential. Like you note that if the bolts were rolled it probably is not an issue. Lots of misinformation out there I just picked it up in a flathead rebuild book somewhere. John Smith advised me on using 10 ft-lb on the studs rather than torquing to the thread size spec.

    TheOldHokie    Posted 04-28-2022 at 15:49:00 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Head Bolts/Studs
  • John's site probably has teh exact changeover date/SN. Studs 10 lb-ft is about right - finger tight is the the general rule.

    TOH

    TheOldHokie    Posted 04-26-2022 at 15:30:34 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Head Bolts/Studs
  • Ford used studs in the earlier models and switched to bolts with the 8N I think. The bolts are easier to deal with and will works just as well as the studs. Adjust your tightening torque accordingly.

    TOH

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