Bad Stud thread

D

DBSHELTON

Senior Member
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!
 
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.
 
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.
 
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?
 
I broke a stud off when changing them out. I drilled out the hole and tapped to the next size (1/2" IIRC) then made a stepped stud which I later found out that you can buy. Doesn't matter, i would have made mine anyway. I used my mag drill as jack suggested to drill and tap the hole to ensure that it was straight. Using the head as a guide would work as well. No real need to monkey around with help coils or inserts. You have to drill and tap it anyways, just put in a oversized base stud.
 
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
 
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.
 
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!
 
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.
 
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 .
 
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katy said:
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.
Click to expand...


Even a Graphite composite gasket?
 
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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.
 
DBSHELTON said:
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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Exactly what is the reason why you cannot reuse the first head gasket?

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.
 
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.
 
BRENT in 10-uh-C said:
Exactly what is the reason why you cannot reuse the first head gasket?

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.
Click to expand...

Didn't he mention he had a Graphtite head gasket?
 
DBSHELTON said:
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?
Click to expand...

Just for your information, 75 is a very conservative number for testing deck threads on a flathead Ford. We test at 100 ft lb.

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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