Broken bolt...... yikes

MTCK

Senior Member
Location
Fairbanks AK
Hey guys, haven't been around in a while, but I have a good one for you all. I have the engine (SBC) out of my 83 1/2 ton right now, and just put a new cam and some other stuff in it. When I was putting the bolt that runs through the pulley and harmonic balancer, I noticed about 3/4 of the way in, that it started to give me a lot of resistence. I probably should have replaced the bolt as the threads were getting worn, but hindsight is always 20/20. I tried to back it out and it sheared off about 2/3 of the way in. This bolt goes directly into the crank. I'm thinking that I will have to drill out the bolt, and retap the hole, but wanted some opinions before I started doing this to my crank. The engine is on a stand, so it's easy to work on, and this isn't my primary transportation so I'm not in a hurry, and want to do it right. Should I have a machine shop do it, to make sure everything stays balanced correctly. Thanks for the input.

Marcus
 

CT18fireman

Banned
Location
Western CT
Try an extractor. It may come out. Next step would be to use a helicoil. I have had both work.

If nothing else a machine shop should be able to help you.

How is the weather up there?
 
OP
M

MTCK

Senior Member
Location
Fairbanks AK
I thought about an extractor, and will start there. What is a helicoil? I haven't heard of one of those. The weather here is typical for a Southeast Alaskan summer. Quite a bit of rain, with nice days sprinkled in between. The high temps are usually in the 60's when it's overcast or raining, and high 70's to low 80's when it's clear and warm out. It's a nice climate for working outside, not too hot or too cold. A good set of raingear is a must. FYI the fishing and crabbing has been excellent this summer. :D

Marcus
 

CT18fireman

Banned
Location
Western CT
A helicoil is a thread repair insert. By drilling the hole larger then it was, you can then tap and thread a coil of metal in. Then the original size bolt can be used. Very strong and commonly used in repairing spark plug and manifold threads in heads.
 

Pelican

2000 Club Member
When I'm in your position, I try the extractor route, usually with limited success. When that fails, I drill out the bolt as much as possible without hitting the threads and then get the moto-tool out. I grind away one side of the bolt until the threads just begin to show. By now the bolt is weak enough that you can collapse it to the center with a hardened prick punch. A sharpened masonry nail will work if you don't have the punch. Once it's punched to the center, you can usually back it out with needle nose pliers.

With this remedy, if your threads weren't damaged you can still salvage the original hole and chase out the original threads.
 

CT18fireman

Banned
Location
Western CT
I have tried that approach with success as well. Whatever you do make you that you have nice clean threads and a new bolt before reassembly.

Let us know what happens.
 
OP
M

MTCK

Senior Member
Location
Fairbanks AK
Thanks for all the responses guys. I tried the extractor without success, and the next try will be the helicoil. I haven't had much time to work on it, as things are crazy around here during construction season. I will keep all of you posted.

Marcus
 
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