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Freewheeling 
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Joined: 05 Nov 2017
Location: Wisconsin
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 Topic: Flywheel and pressure plate bolt spec IB
Posted: 27 Jul 2024 at 10:24pm |
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I want to install the flywheel and pressure plate on my IB with new bolts. The existing bolts are not marked which leads me to believe they are Grade 2. I'm told the flywheel torque spec is 50 lbs. which would be a Grade 5. The top 3 threads on the pressure plate bolts are flat and appear to be stretched which I'd expect on a 70 year old bolt especially if Grade 2. I'm cosidering at least a Grade 5. What was the factory spec on these bolts?
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DrAllis
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Joined: 12 Sep 2009
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Posted: 28 Jul 2024 at 6:51am |
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Use gr 5 minimum or better yet gr 8.
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Gary Burnett
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Posted: 28 Jul 2024 at 7:15am |
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With something like that no reason not to use grade 8
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Steve in NJ
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Location: Andover, NJ
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Posted: 28 Jul 2024 at 9:17am |
I third the motion! I wouldn't use anything but grade 8 especially in the engine or drivetrain. Sheetmetal and or panels, grade 5 is fine.
Steve@B&B
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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife
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Freewheeling
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Posted: 28 Jul 2024 at 10:42am |
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I agree but I'm just wondering what the factory spec was. The grade will also give me a clue to the torque spec. For example, if the pressure plate spec was a grade 2 then I can use a grade 8 but would torque it to 9 rather than 25 lbs/ft . SAE J429f grade marking standards were first published in 1949 so its possible that no marking doesn't necessarily mean the bolts were grade 2.
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TramwayGuy
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Posted: 28 Jul 2024 at 10:56am |
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A grade 8 bolt screwed into a cast iron flywheel is used is overkill. And in fact because it cannot be torqued properly, might be worse than a lower grade bolt.
I would use a grade 5 at most, and secure it with a bit of blue loctite.
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Phil48ACWC
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Location: Vermont
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Posted: 29 Jul 2024 at 6:13am |
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Go to Tractor Supply and get Grade 8 bolts and be done with it. Grade 8 may be a little overkill, but do you want to split the tractor down the road because of a bolt failure? A little Loctite is a good idea and will give you even more peace of mind.
Edited by Phil48ACWC - 29 Jul 2024 at 6:25am
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Steve in NJ
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Posted: 29 Jul 2024 at 8:52am |
Sorry, but using Grade 8 bolts isn't overkill in engine, chassis or drivetrain applications. Use the same torque specs with either a shakeproof washer or locktite or both. You won't have any problems... Steve@B&B
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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife
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Freewheeling
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Posted: 29 Jul 2024 at 2:38pm |
Great discussion guys. I tend to agree that an 8 might be a problem if torqued to the max of 25 lbs/ft in cast iron. Cast is weaker than the steel bolt and it's likely to strip the cast threads. Also the 18 threads per inch on the 5/16 UNC is still quite fine for a cast application, IMO. I'm going to contact a couple old Allis dealers and an even older Allis factory worker if he's still alive. I'll share what I find. 
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Fred in Pa
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Posted: 29 Jul 2024 at 2:57pm |
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WOW !!!! This is not a Hi Performance machine ,grade 8 torqued to spec. in a good cast thread is all that's needed . Good luck on on your journey.
Edited by Fred in Pa - 29 Jul 2024 at 3:05pm
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He who dies with the most toys is,
nonetheless ,still dead.
If all else fails ,Read all that is PRINTED.
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Freewheeling
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Posted: 29 Jul 2024 at 3:04pm |
I know. It's the old perfectionist gear head in me. 
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DrAllis
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Posted: 29 Jul 2024 at 3:29pm |
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If you're worried about stripping the threads in the flywheel (and you SHOULDN'T BE) then, you better loosen all your cylinder head bolts because they are torqued to 75-80 ft lbs !!!!! and in a Harvey diesel engine the head bolts are 165 ft lbs and never have the threads give up in the block !!
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Freewheeling
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Posted: 29 Jul 2024 at 6:11pm |
OK here's what I've learned. New Agco bolts for the model B pressure plate are Grade 5. George, the Allis employee died last year at 92. He started building B's and had a couple of hs own. Grandson looked at his shop notes and found pressure plate torgue @ 15 lbs/ft. though he said he never saw gramps use a torque wrench. So Grade 5 it is gentlemen. Cheers! 
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