Sheared Off Bolt [Tranny to Engine]-Advice Please

[KVH]

I noticed for the first time that there's a bolt stuck in the back of my engine with its head sheared off. It's the top bolt of the transmission bell-housing. It doesn't act as a dowel because it's flush to the engine.

While on auto-pilot I center punched the bolt and drilled a hole through the center of the bolt thinking I could extract it with an easy-out.

No luck so far. It won't move.

I think I hit it dead center, but on my back, upside down in a contorted ball, I'm not sure.

Any ideas on how to get that remnant bolt out of there?

thx

 

[DNK]

Someone must have installed a bolt with out it head

Keep drilling larger holes till you get to that 5/16" tap size and ream it out

 

[sp53]

I have had good luck with those reverse drill bits when it binds it twist it out. Moreover, if you did not get this one you would still be ok. You do not need it, and you could even glue a head on there if it was going to be a 100 point car. I know what you mean though. I usually go after them too.

 

[DNK]

They never had a head
Actually some say it is VERY important for the correct alignment, Eng-Trans

 

[JerryVV]

I'd be tempted to leave it alone. The left hand drill idea is good but if it's really stuck that may not work either. Drilling too deep could go into somewhere in the block that you'd rather not explore so be careful and mark the depth by using another hole as a reference.

Really just leave it as is, you'll be fine.

 

[TR3driver]

If it is the top center, then it was originally a short 5/16" stud, rather than a bolt. Not used for alignment (the alignment is set by two precision dowels, 3/8" diameter as I recall, that are off to the sides). IIRC the stud had coarse threads on the end that goes into the block, and fine threads on the end that sticks out; so it's possible that some DPO tried to install a fine thread bolt that snapped after being forced into the coarse threads.

I don't think it's all that critical; still, that joint was never any too strong (the factory beefed it up several times with the larger engines) and I would want to replace it if possible. It's also a long way before you hit anything important, and even then it's only the water jacket, so I wouldn't worry too much about drilling through. Just limit the depth to 1/2" or so and you'll be fine. It's got to be at least 1" to break through into the water jacket, and no catastrophe even if you do. Just smear some sealant onto the new stud and go on. (Don't forget the refill the coolant though )

I've never had much luck with easy-outs. I've read of a technique where you basically weld a nut onto the end (by holding the nut in place and filling the hole with weld material), but of course that requires access to a welder and welding under some considerably less than optimum conditions. So I'd first try the left-hand drill bit trick. If that doesn't work, keep drilling larger in small steps until you can see the threads on one side of the hole, and then pick out the remains (with a dental pick).

If that doesn't work out, then I would probably install the gearbox and use it as a guide to drill & tap for a "Helicoil". The drill should just fit through the hole in the gearbox (to put the hole in the right place in the block). The tap will cut into the gearbox slightly, but IMO not enough to hurt anything. (I installed a Helicoil for one of the starter bolts this way, many years ago, and I've never had a problem with it.) But if you want, you could remove the gearbox after the hole is drilled, to tap & install the Helicoil. If you do install the insert with the gearbox in place, be sure to turn it in far enough to be entirely inside the block. (One way is to make a mark on the shank of the installation tool, the thickness of the gearbox flange away from the end of the insert.)

If you do decide to leave it as-is; then make sure all the other fasteners are in good shape, with new lockwashers and locating dowels securely installed.

Good luck, no matter which way you go!

 

[DNK]

Sorry,....thought there was 3

 

[KVH]

I think I got that bolt started right in the middle, but that my angle was off as it went in. The engine of course sits at an angle and I tried to compensate and estimate the angle as I drilled.

Anyway, I can't get anything accomplished with an easy-out. It just does nothing for that bolt. Would an impact driver help or make matters worse?

I still have the transmission out, so I've got some room to maneuver for a helicoil, but without pulling the engine I'm really not sure I'll get the hole square enough so that I'll have it lined up properly with the transmission bell housing hole.

I'm not looking for an excuse to pull the engine but I have to wonder how forgiving a helicoil will be on the bolt angle.

Of course my preference would be to get that bolt out and find the old threads still intact, and avoid the helicoil altogether.

 

[glemon]

I got a set of extractors thinkg they would be the bees knees for getting out broken nuts, but have had no luck with them the couple of times I have tried.

I have had best luck with the progressively larger drill bit method. Oftentimes as I get very close to the diameter of the stuck bolt the remanants sort of fall apart and or screw themselves out.

 

[TR3driver]

Would an impact driver help or make matters worse?

Worse, IMO. Normally the impact helps loosen the screw/nut, but in this case it helps tighten it (the easy-out expands the bolt, locking it tighter into the hole). And if you break the EZout, things will get a whole bunch worse (they are too hard to drill with ordinary methods).
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
I still have the transmission out, so I've got some room to maneuver for a helicoil, but without pulling the engine I'm really not sure I'll get the hole square enough so that I'll have it lined up properly with the transmission bell housing hole.

I'm not looking for an excuse to pull the engine but I have to wonder how forgiving a helicoil will be on the bolt angle.
[/QUOTE]
Which is just why I was suggesting using the gearbox as a guide. It has to be both square, and on-center, or you're going to have problems getting things back together. But by drilling through the existing hole in the flange, you're guaranteed that the stud will fit through it; even if the result is slightly off from the original location. IOW the sides of the drill will ream the bellhousing hole to match the engine block hole.

A helicoil is actually stronger than the original hole, so there isn't going to be any extra flex or margin for error. There is a little margin, because the stud wasn't a tight fit in the hole to begin with.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
Of course my preference would be to get that bolt out and find the old threads still intact, and avoid the helicoil altogether.
[/QUOTE]
Which is still a possibility. As glemon said, frequently the bolt will fall apart as you get close; but even if it doesn't crumble on its own, it will crumble with some persuasion from a dental pick.

 

[DanB]

Can you get a torch to it? Heat the block around it and try the easy out if you can get it to bite. There is probably loc-tite on the stud, and the heat will release it.

 

[KVH]

Got it! I think.

I drilled it out more, tried a pick but couldn't find a shoulder. Then carefully ran a tap through it. I know that may have been risky but it seems to have wound the thin wall right out. I wish I could say I hit it dead center, but I'm not sure.

It looks clean. The test will be if it holds with some torque, which I'll try tonight.

An easy out would have been nice--if it would ever work. This is the third time I've failed with an easy out. Maybe high heat would have helped. I don't have a torch, and if I did, I'd be posting something like,"How do I fix my heat-damaged block?"

Thanks for all the good advice folks.

 

[Darrell_Walker]

An easy out would have been nice--if it would ever work. This is the third time I've failed with an easy out.

I'm sure someone, somewhere has had luck with easy outs, but I've never heard of them!

I am quite sold on the left-handed drill bit, that has worked every time for me. I still wonder why it took me so long to get a set!

-Darrell

 

[dklawson]

I asked for a set of LH drill bits for Christmas one year. At first my family thought I had made the whole thing up. Then I gave them a web link where they were for sale at Northern Tool. They have saved me several times now... most recently getting the steel oil gallery plugs out of the GT6 block. However, just like regular drill bits, start small and work up to larger diameters for the best results.

Regardless, I'm glad you got the broken part out and I hope it is a straight enough hole that you have no alignment problems when you put the gearbox back in.

EDIT: Northern still has them... inexpensive and more expensive.
https://www.northerntool.com/shop/tools/product_34761_34761
and
https://www.northerntool.com/shop/tools/product_200384104_200384104