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Subject: 9N main bearing studs

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JimN    Posted 09-28-2020 at 11:54:18 [URL] [DELETE]        [Reply] [Email]  
  • 9N main bearing studs
  • New guy here...
    Looking for where I can purchase new main bearing cap studs for a 9N. Steiner doesn't have them and the used part places I have tried aren't willing to pull them. I don't want to just stick bolts in there, I am looking for the correct double threaded with the proper diameter in the middle for centering the caps properly.
    Anyone have any, or know where I can get them?
    I really only need two middle ones, but wouldn't mind a set..

    Thanks!
    Jim

    TheOldHokie    Posted 09-29-2020 at 06:10:37 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • Dorman 675-082, 1/2-13 x 1/2-20 x 3.00" OAL. Base end thread is .750" shoulder is .250", and top end thread is 2.00". I am quite sure you can make that work.

    TOH

    Tim Daley(MI)    Posted 09-29-2020 at 06:24:52 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • The main thing when using aftermarket/longer stud lengths is to not bottom out the center shoulder on the part going into it and that there is enough thread length to secure the hex nut with. Like Dan said, if hex bolts will work, I'd opt to go with those. Bolts would also be cheaper to buy than studs and you wouldn't have to muck around with lengths much.


    Tim Daley(MI)

    Tim Daley(MI)    Posted 09-29-2020 at 04:43:05 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • Studs are designed mostly with a course thread end and a fine thread end. The course thread always goes into the cast iron part and the fine end always fastened the hex nut. Are these the parts you seek:

    9N-6345; 1/2-13 x 1/2-20 x 2.84 L, Drilled, 5 req'd.
    9n-6346; 1/2-13 x 1/2-20 x 3.84 L, Drilled, 1 req'd.

    FORD used specific lengths in all their fasteners, most in sizes not sold today so getting the LENGTH correct is important. There are a few suppliers that stock the odd FORD lengths, I had a list somewhere, so perhaps someone else will chime in.

    27/32 is .8437" and is rounded off as .84, NOT a standard size, and .94 is 15/16 (9375") rounded off, and NOT a standard size today.


    Perhaps you can do some more research in the archives and use hex head bolts to see what others used.

    Tim Daley(MI)

    Zeked (OR)    Posted 09-29-2020 at 11:20:03 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main beariing stud
  • Tim (and others). What is a “drilled” stud? What makes it different and what problem does it solve?

    Thanks
    Zeke

    TheOldHokie    Posted 09-29-2020 at 17:40:38 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main beariing stud
  • The tip of the stud is cross drilled for a cotter pin. Typically this is used in conjunction with a castellated nut as a safegaurd against loosening.

    TOH

    Zeke(OR)    Posted 09-30-2020 at 12:32:01 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main beariing stud
  • Thanks, Hoke.... I looked on the web and Wikipedia no joy...
    But now I know 😀

    TheOldHokie    Posted 09-28-2020 at 19:00:14 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • Personally I'd use cap screws but I am confident Dorman sells something equivalent. Measure and shop the Dorman site.

    TOH

    JimN    Posted 09-29-2020 at 19:28:18 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N main bearing studs
  • The reason I would like to use the correct studs is they have a correct snug fit at the middle “shoulder” to properly center the bearing cap around the crankshaft. Bolts or cap screws seem to have too much play and would allow the bearing cap to be off center.
    I also am getting the block and caps line-bored and need the caps centered perfectly during that process.

    TheOldHokie    Posted 09-29-2020 at 22:26:11 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • I dont think the studs are anything special and I think you are worrying about something that does not matter. Have you asked your machinist about this? The bore does not have to be centered between the studs. It just needs to be round and straight. It can and will be high, low, left, right, and out of square regardless of what studs you use. This is due to setup tolerances in the process. That is true with the OEM bore as well and why caps dont interchange.

    TOH

    JimN    Posted 09-30-2020 at 07:18:49 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N main bearing studs
  • The machine shop is looking for the studs as well. He believes they should be correct. If your tolerance is a max of 0.0025 and you have slop of 10 times that because you just stuck a bolt in there, it wouldn't be right, maybe cause the caps to shift, maybe create a wear spot in the bearing inserts.
    Does the 8N have the same studs as the 9n? Somebody should have a worn out or cracked engine sitting around...

    TheOldHokie    Posted 09-30-2020 at 08:32:39 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • With all due respect to your machinist torqued main caps are not going to shift during a line hone. Simple table clamps with no registration mechanism whatsoever reliably hold heavy machining forces far far greater than that.

    So what exactly were factory tolerances? I have looked at a number of original Ford prints and there is zero chance the factory held cumulative stud hole spacing tolerances to anything close to .002. It simply wasn't practical given the production volumes and machine tools being used. For precision close fits the old prints typically specify a tolerance of .003 on EACH hole. That translates to a potential cumulative tolerance of .006. The line boring and honing operation with the caps bolted into those holes effectivel elininates that error.

    If your concern is registration during reassembly after honing consider knurling the shoulders on the studs. You can easily close up the bolt hole clearances and essentially make them a "snap" registration fit in the same fashion the snap fit on modern blocks with distorted/loose cap registration recesses are restored by peening with a chisel.

    Personally I'd be more concerned by the integrity of the old studs that have been stretched and distorted by 70 years of beating, heat cycling, and metal fatigue.

    JMO,

    TOH

    JimN    Posted 09-30-2020 at 09:29:09 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N main bearing studs
  • I get what you are saying, and have considered all of that, the machinist isn't concerned about parts shifting during his work. The .0025 is bearing clearance like you would measure or check with plastigage. Why would I want to accurately machine my crank and have it line-honed (new caps) and then install it with the caps not necessarily centered.....
    I basically plan to do this the correct way with properly sized studs. That is not up for debate.
    My question to this forum was where can I find the correct studs..

    Thanks, appreciate the input,
    Jim

    TheOldHokie    Posted 10-01-2020 at 09:02:07 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • You piqued my interest enough to make me do some checking. I have an old cracked 9N block in the shop and I pulled a stud and cap to check the fits. The shoulder on the stud measures .499x and essentially functions as a .001 undersize dowel pin:

    Now the interesting part. The holes in the caps are clearly tapered! At the parting line they measure .501/.502 and at the top about .512/.513. At first I thought this might be wear but all three caps I checked have essentially identical amounts of taper. When the stud is inserted in the holes it is a loose free fit and will wobble considerably longitudinally but has a scant .001/.002 radial clearance at the parting line. After thinking about this for a bit I concluded the Ford engineers were being clever and intentionally tapered the holes to facilitate assembly - the fit is loose at the top to allow for minor stud misalignment which is always a royal PITA. The fit closes up at the parting line to act as a register for the bore. Now that is a guess - educated perhaps but unconfirmed and I'm sticking to it unless someone can offer a better explanation for this geometry

    But we still have something on the order of .002 radial play at the parting line which does not seem reasonable. Going back to the block when I put the cap on the studs it starts easily but as it gets most of teh way down I have to tap it with a hammer to get it to seat and once seated there is no detectible radial play - it is seemingly a slight interference fit. What's up with that?

    Once again I am going to guess that Ford used the hole spacing in the caps and block to eliminate that radial play and create that slight interference. By spacing the studs a couple thousandths wider or narrower than the holes in the cap and carefully choosing the tolerances for the spacing they could achieve a gauranteed tolerance stackup of something on the order of .000 to .002 interference and still keep individual part tolerances in the very manageable low thousandths. We would need to purchase a copy of both prints to see if that guess is correct - anyone curious enough to pony up the $100??

    Which brings me back your original question. I have 4 good short OEM studs that you can have for the cost of postage if you want them.

    TOH

    TheOldHokie    Posted 09-30-2020 at 17:11:23 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • Personally I think a good machinist owns a bore gage and knows how to use it to accurately measure bearing clearance. Plastigage is for ill equipped amateurs.

    An engine builder can easily get within the .0025 clearance on a line bore. That would be the outer limit of what I was happy with.

    If I understand your concern it is cap registration on reassembly after machining the caps.The L-head design does not have a cap registration recess in the block like a modern engine. Which begs the issue of what the engineers felt was needed.

    I see no need for sourcing beat to death OEM studs to achieve that end. Any engine builder worth his salt should be able to make after market studs act as a register. If you believe it is important knurl the shoulder to get an interference fit on the caps. I think that is as good as it gets given the design.

    TOH

    Jim Nester    Posted 10-08-2020 at 18:16:44 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N main bearing studs
  • Sure, I am interested in the studs.
    How do I contact you?

    TheOldHokie    Posted 10-08-2020 at 19:57:53 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N main bearing studs
  • oldhokie@windyridgefarm.us

    TOH

    Jim Nester    Posted 10-12-2020 at 20:23:00 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N main bearing studs
  • Sounds good (sorry for the delay).
    email sent
    Thanks!
    Jim

    Jim nester    Posted 10-20-2020 at 22:51:09 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N main bearing studs
  • Do you still have those studs available?

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