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12-05-2020, 06:57 PM | #1 |
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Location: Kountze,TX
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Bad Stud thread
Trying to finish my spare engine and was torquing the head nuts. Everything went fine at 25ft lbs, 36 ft lbs, 48 ft lbs, and then finishing up at 55 ft lbs and the threads failed on #14 on the chart!!! Damn, now I gotta pull the head and helicoil that hole. Worst part is wasting the new head gasket!
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12-05-2020, 07:23 PM | #2 |
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Re: Bad Stud thread
At least it's a hole you can dig yourself out of!
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12-05-2020, 11:34 PM | #3 |
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Re: Bad Stud thread
Yeah that is a bummer.
If you're drilling free hand for the helicoil make sure you have an extra set of eyes watching 90 degrees from where you are so as to make sure it's drilled straight up and down.
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12-05-2020, 11:51 PM | #4 |
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Re: Bad Stud thread
Better yet rent a mag drill from the local rental. Set it down on the deck,line it up,turn the magnet on and drill square every time.Consider a timesert instead of a helicoil, its a better product.
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12-06-2020, 06:47 AM | #5 |
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Re: Bad Stud thread
I am going to use the head for a drill guide since the drill bit for the helicoil will fit through.
Before I pull the head, should I over-torque the nuts to maybe 75ft-lbs to make sure all the threads are good and this won't happen again? |
12-06-2020, 08:29 AM | #6 |
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Re: Bad Stud thread
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12-06-2020, 08:36 AM | #7 |
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Re: Bad Stud thread
No don't over torque to 75 foot pounds. Absolutely not!
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12-06-2020, 08:52 AM | #8 |
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Join Date: Aug 2013
Location: Long Island NY
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Re: Bad Stud thread
Bratton's supplies a tool jig kit #8235 that allows you to drill out the stud without disturbing or removing any of the other studs. The jig comes with a locating guide and bushings, a burr to center the hole, drill bit and two taps including a guide bushing to install a Helicoil. The DRILL BIT STINKS, BUY A CARBIDE ONE. I just completed doing 3 studs in a little over an hour. With your stub breaking at such a low torque setting you might consider replacing all of the other studs.
Take the job slow and easy Good luck |
12-06-2020, 09:57 AM | #9 |
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Re: Bad Stud thread
I broke a stud before. I used the head as a guide with the drill bits wrapped in electrical tape to bush them to the hole. you can also use tape to make a mark of depth on your drill bit. I went without a depth mark and drilled through my block to the water jacket, and have to thread seal that stud now. dont make that mistake.
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12-06-2020, 10:30 AM | #10 |
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Re: Bad Stud thread
I went ahead and drilled the threads out through the head for the helicoil. Very easy since the hole in the head was the correct size for the 29/64" bit.
In my poor boy days I would drill the head out to 17/32" for the tap to fit through and install the Helicoil through the head. LOL! |
12-06-2020, 11:23 AM | #11 |
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Re: Bad Stud thread
If you didn't put any sealer or paint on the head gasket it can be re-used.
Put it in the oven or bar-b-que for 15-20 minutes and then let it air cool before re-installing it.
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12-06-2020, 12:00 PM | #12 |
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Re: Bad Stud thread
I bought a rebuilt (so they said ) engine very cheap . It was cheap because someone had put a helicoil in but not straight . I screwed a new stud in and it looked like the leaning tower of Pisa . HHMMM I thought what to do, what to do . The helicoil was large meaning I did not think I could go the next size up if there was one . So a master plan sprung into action I screwed a new stud hard home in the helicoil and took a template of the lean and marked the stud with a sharpie . Put the stud in the vise with two UNC nuts on the bottom and with a suitable tube cold bent the stud to match the template . Replaced the stud put the head on and torqued to 65 ft/lbs and let it set for a while all looked good .I think this is a permanent cure I cant see this large helicoil pulling out of the block and the bent stud has not lost vertical strength . I checked the motor out new pistons etc etc so was rebuilt I bet the guy in the shop got it in the neck afterwards . In service it will be torqued to 55 ft/lbs
John in cold dark Suffolk County England . Last edited by john charlton; 12-07-2020 at 06:10 AM. |
12-06-2020, 12:38 PM | #13 | |
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Location: Kountze,TX
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Re: Bad Stud thread
Quote:
Even a Graphite composite gasket? Last edited by DBSHELTON; 12-06-2020 at 06:01 PM. |
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12-06-2020, 03:26 PM | #14 |
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Re: Bad Stud thread
Good Job, John...I would not have thought of that...Ernie in Arizona
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12-06-2020, 05:32 PM | #15 |
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Re: Bad Stud thread
Bratton's has head studs with an oversize thread (½-13) on one end if you ever find you need it. I would think that would be better than a heli-coil.
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12-06-2020, 06:01 PM | #16 |
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Location: Kountze,TX
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Re: Bad Stud thread
I figured since I had another gasket I would go ahead and use it. Looks like I was successful on my 2nd time.
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12-06-2020, 07:08 PM | #17 | |
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Re: Bad Stud thread
Quote:
Unless you unnecessarily coated it with some type of sealer that caused it to tear when removed, then reuse it. If you are worried, then anneal it and it will be ready to reuse. |
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12-06-2020, 07:38 PM | #18 |
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Join Date: Sep 2019
Location: Kountze,TX
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Re: Bad Stud thread
If I didn't have another one I would have given it a couple of coats of copper spray and re-used it. Heck, I have even used aluminum spray paint successfully. I did keep it just in case.
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12-06-2020, 07:47 PM | #19 |
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Re: Bad Stud thread
Didn't he mention he had a Graphtite head gasket?
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12-06-2020, 08:53 PM | #20 | |
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Re: Bad Stud thread
Quote:
Testing should be done while doing machine work on the block and before any cleaning. This way you are assured there will be no drilling or machining after assembly with the consequent chips getting inside. Threads should be chased with a tap, not a chaser. You CAN NOT get an accurate torque reading with rust and scale left in the threads. |
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