Broken bolt in front of crankshaft

[ElCoSix]

Aargh!
I have a 67 El Camino with the 250 inline six that I'm restoring. I'm going to use the six for now - and maybe forever. I'm trying to get a broken bolt out of the crankshaft without tearing it apart. There's no radiator or even core support yet, so I can get right at it. I was thinking that if I had a new bolt, I might be able to get a machine shop to drill right through the center so it would make a nice guide to drill in the very center of the broken bolt. Then I could start the bolt in and drill a pilot hole right where it's supposed to be. That way I could try a reverse direction drill bit or some kind of extractor. Does anyone know the thread size and pitch of the bolt or where I can get that information? Or better yet, does anyone have one? Or any other ideas for getting the broken bolt out?
Thanks a lot,
Scott

[Steeveedee]

How deep down is the bolt broken off? You might have enough room to stuff an aluminum (so it doesn't trash the threads) bushing in it. I think the threads are 3/8" or 7/16". You can try a couple of bolts to check that. Then get a bushing from the hardware store with a 1/4" ID and whatever the OD is. You might have to go to a 3/16" ID. This is all contingent on there being enough depth for the bushing.

[toolboxchev]

Originally Posted by ElCoSix

Aargh!
I have a 67 El Camino with the 250 inline six that I'm restoring. I'm going to use the six for now - and maybe forever. I'm trying to get a broken bolt out of the crankshaft without tearing it apart. There's no radiator or even core support yet, so I can get right at it. I was thinking that if I had a new bolt, I might be able to get a machine shop to drill right through the center so it would make a nice guide to drill in the very center of the broken bolt. Then I could start the bolt in and drill a pilot hole right where it's supposed to be. That way I could try a reverse direction drill bit or some kind of extractor. Does anyone know the thread size and pitch of the bolt or where I can get that information? Or better yet, does anyone have one? Or any other ideas for getting the broken bolt out?
Thanks a lot,
Scott

Machine shop would be able to get it out better as they most likely would be able to put a jig on it and keep a drill centered to use an EZ out.

[ElCoSix]

Actually, that is a better idea than trying to drill the bolt. Thanks for that. The broken bolt sticks out almost to the top of the threads. I can get maybe a half of a turn in with a bolt - not even enough to tell if it's the right thread pitch. That's part of my problem too. But if I can clean out some of those threads a little deeper somehow maybe I can stick a bushing in there - even if only a little bit - it could help guide the drill bit. I feel like it's worth doing a lot of figuring out and doing a lot of work to get this out without tearing anything apart.
Thanks a lot - I'll post if I succeed!

[Grumpy old man]

Can you post a pic? I haven't seen a 67 -250 with a Hb bolt ,Unless someone already drilled and tapped it ? All the ones I have are pressed on ?

[it2castelo]

If you do decide to drill it, put a stop on your drill bit. When you get through the broken bolt your momentum will make you start drilling into the crankshaft. When you pull the bit out, oil will flow out. Then you need to replace the crankshaft. Don’t ask how I know this.

[Steeveedee]

We need a picture. Or two!

[cleszkie]

If it were me, I'd try welding a bolt to the broken end and back it out that way. Probably need to use a slightly smaller diameter bolt in order to make room to weld if the bolt is broken off below the face of the crank shaft. Before attempting to back the broken bolt out, I would also soak it with some penetrating oil. I would also probably apply some low heat to the crank to help loosen things up.

[geezer#99]

Originally Posted by Grumpy old man

Can you post a pic? I haven't seen a 67 -250 with a Hb bolt ,Unless someone already drilled and tapped it ? All the ones I have are pressed on ?

The grump is right!
No need to remove a bolt by any method that isn’t there.
They were pressed on.

[DWX 9929]

Weld a nut to the broken bolt. Same size as the bolt. Weld down through the center. Let cool some then tap towards the bolt several times. May take several tries. When bolt starts to turn work it back and forth as you remove it.
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[Grumpy old man]

I wonder how many guy's will be trying to weld a nut to a "broken HB bolt" that doesn't exist on the 250 crank ?

There is NO bolt on the 67 truck 250 crank .

[DWX 9929]

Originally Posted by Grumpy old man

I wonder how many guy's will be trying to weld a nut to a "broken HB bolt" that doesn't exist on the 250 crank ?

There is NO bolt on the 67 truck 250 crank .

Sorry if I gave bad advice. Being unfamiliar with the crank, I don’t know if there’s a bolt or not. I was just advising how to get any broken bolt out.
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[cleszkie]

Originally Posted by Grumpy old man

I wonder how many guy's will be trying to weld a nut to a "broken HB bolt" that doesn't exist on the 250 crank ?

There is NO bolt on the 67 truck 250 crank .

I don't think the OP mentioned that it was a harmonic balancer bolt. But he definitely seems convinced he has a broken bolt of some sort. Perhaps he is confusion the crank with the cam, and he is actually dealing with a broken timing chain gear bolt in the cam. Without pictures, nobody will know for sure what is going on here.

['68OrangeSunshine]

Originally Posted by cleszkie

I don't think the OP mentioned that it was a harmonic balancer bolt. But he definitely seems convinced he has a broken bolt of some sort. Perhaps he is confusion the crank with the cam, and he is actually dealing with a broken timing chain gear bolt in the cam. Without pictures, nobody will know for sure what is going on here.

L6s have a gear-to-gear set. No chain.

[ElCoSix]

Hmm. Weird. I won't be near my project until Saturday and I'll try to do some pics that are nice and clear and post them. Thanks a lot for all the responses!

[ElCoSix]

By the way, would any other inline six have been used in a '67 El Camino? And would any of them have had a bolt? There is a woodruff key there, so it does seem the HB would be pressed on, but there's also a hole in the end of the crank with something in there that appears to be a broken bolt. Looks like only 3/8 or 7/16 diameter.

[cleszkie]

Originally Posted by '68OrangeSunshine

L6s have a gear-to-gear set. No chain.

OK. But one of the gears is bolted to the cam. That was my point.

['68OrangeSunshine]

Originally Posted by cleszkie

OK. But one of the gears is bolted to the cam. That was my point.

Actually IIRC, the gear on the cam is pressed on with a frozen cam and super-heated gear step. L6s are different. Also, 292s have a bolt in the crankshaft to secure the HB. 230/250s don't have a bolt, at least not the early ones.

['68OrangeSunshine]

Originally Posted by ElCoSix

Aargh!
I have a 67 El Camino with the 250 inline six that I'm restoring. I'm going to use the six for now - and maybe forever. I'm trying to get a broken bolt out of the crankshaft without tearing it apart. There's no radiator or even core support yet, so I can get right at it. I was thinking that if I had a new bolt, I might be able to get a machine shop to drill right through the center so it would make a nice guide to drill in the very center of the broken bolt. Then I could start the bolt in and drill a pilot hole right where it's supposed to be. That way I could try a reverse direction drill bit or some kind of extractor. Does anyone know the thread size and pitch of the bolt or where I can get that information? Or better yet, does anyone have one? Or any other ideas for getting the broken bolt out?
Thanks a lot,
Scott

Not all 250s were drilled for a Harmonic Balancer retaining bolt, like the 292s had. Such a [stock] bolt hole would be a 7/16-20 UNF X1.0'' deep thread. Leo Santucci, author of the ''Chevy Inline Six-Cylinder Power Manual'' recommends drilling and tapping the crank snout fot 1/2''x 20NF x 2-1/2''.
[Same as a Chevy V8.]
El Caminos could possibly have a 230 [car] engine, which looks just like the 250 from the outside. Run the ''dress numbers'' stamped in the pad just aft of the distributor hole. The 2- or 3-letter code at the end can tell you.

A retaining bolt for the HB is a great idea on any L6, as that allows you to use a fine-threaded HB installer tool to press the balancer on smoothly, which is a lot better than bashing it on with a deadblow hammer. The cruder assembly method can cause bearing damage if not done right.

[ElCoSix]

Originally Posted by '68OrangeSunshine

Not all 250s were drilled for a Harmonic Balancer retaining bolt, like the 292s had. Such a [stock] bolt hole would be a 7/16-20 UNF X1.0'' deep thread. Leo Santucci, author of the ''Chevy Inline Six-Cylinder Power Manual'' recommends drilling and tapping the crank snout fot 1/2''x 20NF x 2-1/2''.
[Same as a Chevy V8.]
El Caminos could possibly have a 230 [car] engine, which looks just like the 250 from the outside. Run the ''dress numbers'' stamped in the pad just aft of the distributor hole. The 2- or 3-letter code at the end can tell you.

A retaining bolt for the HB is a great idea on any L6, as that allows you to use a fine-threaded HB installer tool to press the balancer on smoothly, which is a lot better than bashing it on with a deadblow hammer. The cruder assembly method can cause bearing damage if not done right.

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[ElCoSix]

Oh! Thanks much! I’ll check those numbers and thanks for the thread size/info. Maybe I’ll try to find Leo’s book while I’m at it.
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