Thread clean up on crank ?
Team Owner
Joined: May 2001
Posts: 29,745
Likes: 3
From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
Re: Thread clean up on crank ? (verskel)
I also would not trust a heli-coil for that. In years of dirt track racing I have seen many a balancer (or even the front part of a crank) come off the engine and end up flying down the track.
Too much stress, vibration and rpms to be using a solution that is not 100% permanent.
Call a machine shop in your area and ask what they do in this case.
Too much stress, vibration and rpms to be using a solution that is not 100% permanent.
Call a machine shop in your area and ask what they do in this case.
Racer
Joined: Jan 2004
Posts: 294
Likes: 0
From: cincinnati oh
Re: Thread clean up on crank ? (motown 71)
Stay away from the heli coil (think of it as duct tape for threads). Call a machine shop, they will be able to weld the hole up and re-cut the threads. Of course you will have to know what the thread size is.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Thread clean up on crank ? (motown 71)
I had a similar problem with a crank and I cleaned up the threads and used a longer bolt and some lock tite, most likey you just screwed up the first 1/2 or so of them.
Drifting
Joined: Oct 2000
Posts: 1,825
Likes: 56
From: Shawano WI
Re: Thread clean up on crank ? (motown 71)
A heli-coil or to drill and tap the hole to the next size is an acceptable repair for stripped threads. I have fixed many crankshafts with pulled threads with both type of repairs with no problems. The balancer is an interference fit to the crank. The bolt is strictly a secondary precation. If the balancer fits the crank properly and the keyway is in good shape, you don't need the bolt to retain the balancer. Many small blaocks and big blocks did not have the bolt installed from the factory.
The heat treat on a crankshaft is generally only .050 - .060 deep so drilling the crank snout is not a big problem. Make sure you use a good sharp 3 or 4 flute tap and it will tap easily also.
The heat treat on a crankshaft is generally only .050 - .060 deep so drilling the crank snout is not a big problem. Make sure you use a good sharp 3 or 4 flute tap and it will tap easily also.
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Re: Thread clean up on crank ? (motown 71)
I used a tap to clean the threads, think you will find the boogered threads are at the front...once you run the tap through, the remaining threads will be fine, and strong enough to apply the required torque on the bolt.
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Thread Starter
Racer
Joined: Jan 2004
Posts: 340
Likes: 1
From: St. Clair Shores Michigan
Re: Thread clean up on crank ? (GDaina)
Thanks to eveyone who took time to contirbute here.
As stated it is only the begining portion of the threads that are damaged.
so Looks like I will go with running a tap and using lock-tight or maybe a dab of JB weld to. If anyone is interested the thread size on mine is 7/16 20.
Thanks again !!
:flag
As stated it is only the begining portion of the threads that are damaged.
so Looks like I will go with running a tap and using lock-tight or maybe a dab of JB weld to. If anyone is interested the thread size on mine is 7/16 20.
Thanks again !!
:flag