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Old 05-07-2020, 11:42 AM   #1
AnthonyG
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Question 1 Fly wheel 2 PP thread bad

Hi guys, went to reinstall PP on flywheel & Murphy showed up on last bolt! Per 17-20’lb torque spec last bolt stripped thread in flywheel! I know all the options. 1 Different flywheel w/o prob. 2 Helicoil. 3 weld redrilled retap. Or my solution as I have a lathe I went to a 3/8”-16 tap/thread & drilled a concentric hole in the 3/8”-16 bolt to remove weight till same weight as 5/16-18 bolt using balance scale to achieve same weight so it should still be balanced. I don’t like Helicoils. Didn’t wanna heat up flywheel w weld! Don’t think I need new flywheel! So that’s what I did. Engine still out of car. Don’t beat me too much but what do u think of my solution?
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Old 05-07-2020, 12:00 PM   #2
drolston
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Default Re: 1 Fly wheel 2 PP thread bad

Shade tree approach:

Line the stripped hole with a tube of tinfoil and put the original bolt in just tight enough that the lock washer is copressed so it will not come loose. The balance is preserved and the pressure plate could care less that it is fastened with five and a half bolts instead of six.

Alternatively, fill the hole with JB Weld, drill it, tap it, and torque it to about half recommended value.
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Old 05-07-2020, 12:04 PM   #3
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Default Re: 1 Fly wheel 2 PP thread bad

I am not enamored with any of the above approaches. I would use a quality thread insert (Keen-Sert, etc.) and be sure.
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Old 05-07-2020, 12:58 PM   #4
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Default Re: 1 Fly wheel 2 PP thread bad

Hope you don't fly,aircraft are one of the largest users you can find with heli coil approved repair scheme. On a side note welding cast iron and drilling and tapping will be another venture you should eliminate from your offerings.It becomes almost non machinable at best. "Tub" has also given sound advice


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Old 05-07-2020, 02:16 PM   #5
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Default Re: 1 Fly wheel 2 PP thread bad

Try a metric threaded bolt. Sometimes it will grab damaged threads and allow careful tightening when the SAE threads are worn or cross threaded.
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Old 05-07-2020, 03:16 PM   #6
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Default Re: 1 Fly wheel 2 PP thread bad

Make a template and rotate it 60 degrees, redrill and tap. Good as new.
Bruce
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Old 05-07-2020, 04:29 PM   #7
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Default Re: 1 Fly wheel 2 PP thread bad

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Originally Posted by supereal View Post
Try a metric threaded bolt. Sometimes it will grab damaged threads and allow careful tightening when the SAE threads are worn or cross threaded.
Really? On a clutch assembly?
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Old 05-07-2020, 04:32 PM   #8
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Default Re: 1 Fly wheel 2 PP thread bad

I think your fix will work just fine. If your "new" bolt made torque and felt solid doing so, I don't see any reason to worry.


Terry
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Old 05-07-2020, 06:18 PM   #9
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Default Re: 1 Fly wheel 2 PP thread bad

Thx all, I do agree welding cast & trying to reaching is a poor option. Keensert I agree is a good fix but donít think significantly different than my fix which eliminates the extra piece of metal. No way on the drilling tapping a new pattern without a precision mill & turn table, have a horror story w a flywheel I had originally gotten w the vehicle that after several engine pulls & detective work realized it was .090 out of ci centricity causing major vibration due to out of balance condition! I did a test run & used another 3/8-16 bolt like the one Iím using in a junk flywheel I put same thread in & torqued to 30 Ďlbs w no problem. I will use the 3/8-16 bolt I modified to correct weight. 1 out of 5 of u agrees thx Terry, u & me makes 2 outa 5, thatís 40% LOL! Thx all for comments & not spanking me too hard! Being a machinist & having experience in dynamic balancing I believe itíll b fine.
Best all
A
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Old 05-07-2020, 06:37 PM   #10
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Default Re: 1 Fly wheel 2 PP thread bad

It SEEMS pretty evident that some of y'all have never witnessed what's left after a clutch explosion. I remember two different occasions specifically back in the latter '60s, and it ain't nice! One guy lost a leg over it. That's one area that you couldn't make me cut ANY corners. You DO realize that those six bolts have specially-sized shoulders and lengths? Do yourself a huge favor and if you can't afford a new flywheel, at least round-up a good used one. At the very least do as suggested above and re-drill and tap (PRECISELY) at the 60 degree offset...Ö..did I say PRECISELY? And don't just go to Lowes and buy six grade 8 bolts.....get the proper, dedicated pressure plate bolts. But WTF do I know? DD
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Old 05-07-2020, 06:52 PM   #11
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Default Re: 1 Fly wheel 2 PP thread bad

C512>>>I think your fix will work just fine.>>>
AG>>>thx Terry, u & me makes 2 outa 5,>>>


Ditto. Probably makes it at least 3 outta 6 oops 7 now. 8^) Jack E/NJ
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Old 05-07-2020, 06:53 PM   #12
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Default Re: 1 Fly wheel 2 PP thread bad

Quote:
Originally Posted by V8COOPMAN View Post
It SEEMS pretty evident that some of y'all have never witnessed what's left after a clutch explosion. I remember two different occasions specifically back in the latter '60s, and it ain't nice! One guy lost a leg over it. That's one area that you couldn't make me cut ANY corners. You DO realize that those six bolts have specially-sized shoulders and lengths? Do yourself a huge favor and if you can't afford a new flywheel, at least round-up a good used one. At the very least do as suggested above and re-drill and tap (PRECISELY) at the 60 degree offset...Ö..did I say PRECISELY? And don't just go to Lowes and buy six grade 8 bolts.....get the proper, dedicated pressure plate bolts. But WTF do I know? DD
I've witnessed it up close and personal. Hurt like heck as I recall. Both bones in my right leg, well, they turned in to four bones if ya know what I mean.
Scatter shield was installed soon thereafter.
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Old 05-07-2020, 06:54 PM   #13
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Default Re: 1 Fly wheel 2 PP thread bad

Quote:
Originally Posted by cmbrucew View Post
Make a template and rotate it 60 degrees, redrill and tap. Good as new.
Bruce
A template? Really?
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Old 05-07-2020, 06:55 PM   #14
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Default Re: 1 Fly wheel 2 PP thread bad

Quote:
Originally Posted by drolston View Post
Shade tree approach:

Line the stripped hole with a tube of tinfoil and put the original bolt in just tight enough that the lock washer is copressed so it will not come loose. The balance is preserved and the pressure plate could care less that it is fastened with five and a half bolts instead of six.

Alternatively, fill the hole with JB Weld, drill it, tap it, and torque it to about half recommended value.
Yikes!
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Old 05-07-2020, 07:14 PM   #15
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Default Re: 1 Fly wheel 2 PP thread bad

Quote:
Originally Posted by V8COOPMAN View Post
It SEEMS pretty evident that some of y'all have never witnessed what's left after a clutch explosion. I remember two different occasions specifically back in the latter '60s, and it ain't nice! One guy lost a leg over it. That's one area that you couldn't make me cut ANY corners. You DO realize that those six bolts have specially-sized shoulders and lengths? Do yourself a huge favor and if you can't afford a new flywheel, at least round-up a good used one. At the very least do as suggested above and re-drill and tap (PRECISELY) at the 60 degree offset...Ö..did I say PRECISELY? And don't just go to Lowes and buy six grade 8 bolts.....get the proper, dedicated pressure plate bolts. But WTF do I know? DD
The man knows from whence he speaks, as do I. Fortunately for me, unlike Kube's experience, every piece missed me completely. Do yourself and the next owner of your car a favor and get another flywheel...
Ken
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Old 05-07-2020, 07:18 PM   #16
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Default Re: 1 Fly wheel 2 PP thread bad

OK. You can make that 3 1/2 out of 9, because I think what the O/P suggested is the best of the bad ideas.

But it's still a bad idea. I used to drag race too.
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Old 05-07-2020, 07:22 PM   #17
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Default Re: 1 Fly wheel 2 PP thread bad

Ya know, this is yet another of those threads that perplexes me.
Man oh man, I pray some of you guys are never near me on the highway. Some guys should simply put the wrench down, shut the lights off and leave the garage...
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Old 05-07-2020, 08:32 PM   #18
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Default Re: 1 Fly wheel 2 PP thread bad

Wow! There’s the ass kicking I expected! While I still think my plan was viable considering the almost 20% larger hardware, I’ll go w a Helicoil fix staying w original 5/16-18 PP hardware. I asked for ur opinion so. As Ronnie indicated Helicoils r certified repair for threads in aircraft & aerospace industry so gotta b good for old fords
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Old 05-07-2020, 09:57 PM   #19
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Default Re: 1 Fly wheel 2 PP thread bad

And as stated above, always use the correct shoulder bolts on the flywheels designed for them. Personally those flywheels are not difficult to obtain and are not rare. I would junk the flywheel with stripped hole and get another off the shelf.
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Old 05-08-2020, 01:11 AM   #20
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Default Re: 1 Fly wheel 2 PP thread bad

Quote:
Originally Posted by cmbrucew View Post
Make a template and rotate it 60 degrees, redrill and tap. Good as new.
Bruce

Now that's funny! Is a cardboard template good enough? I guess using the pressure plate itself would complicate matters?

Quote:
Originally Posted by AnthonyG View Post
As Ronnie indicated Helicoils r certified repair for threads in aircraft & aerospace industry so gotta b good for old fords

Now there's a perfect example of some good ol' MSM-like obfuscation. What Ronnie "indicates" ain't necessarily the WHOLE story for ALL parts in flyin' flivvers and space ships. With your mind seemingly made-up, I'm not sure why you even wasted your time asking for advice here to begin with. Just try VERY hard to imagine the scary stuff going-on inside that clutch housing with that flywheel/clutch spinnin' at even 2,500 RPMs. THEN try to imagine the tremendous multi-directional forces and loads imposed on those six, lousy 5/16" bolts screwed-into Helicoils when ya raise the RPMs to four grand and enthusiastically engage the clutch! GOOD LUCK, ol' buddy! I wish ya the best!! Just remember what deuce_roadster indicated....used flywheels are NOT hard to round-up. DD
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