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52-fan
03-01-2012, 06:58 PM
My brother had his 289 apart for some upgrades and was reassembling it. He was using a bolt in the end of the crankshaft to pull the harmonic balancer on when the bolt began to turn freely. He thinks the threads in the crank are stripped. Is there a fix or is this crank now junk?

Alan
03-01-2012, 07:31 PM
The thread is a 11/16" X 16. It will take quite a bit of torque before it lets go. Is the engine out of the car? Best to look at the threads with an inspection light or try to run a tap into it and see what happens. You should always use a plug in the crank when pulling on the damper.

rkapteyn
03-01-2012, 07:34 PM
The thread on the bolt probably stripped and the crank will be fine.
Use the proper too; next time.
Robert Kapteyn

52-fan
03-01-2012, 07:49 PM
I have not looked at the crank myself. I asked if he got any work done on the engine and he gave me the news. He is totally bummed about the deal. He tends to get in too big a hurry when doing this kind of thing. I am more methodical, but very slow. Unfortunately, we are not often off on the same day.
I asked him a few more questions. The bolt he was using was out of a 224 which apparently is longer than the 289 bolt. The bolt, unfortunately, is fine. I don't hold out much hope for the threads in the crank from his description.

sweetolbob
03-01-2012, 08:27 PM
To answer your can it be fixed question, Yes. Just go to the local FLAPS and get the proper helicoil repair kit.

When he gets the price, he'll remember next time not to be so muscular. About $50 or so if I recall.

If it's out, a machine shop can do it and assure the hole is straight but I've done it on a couple of SBCs with excellent success.

Bob

Alan
03-01-2012, 09:59 PM
Good luck on finding a 11/16" X 16 helicoil.

sweetolbob
03-01-2012, 10:25 PM
Good luck on finding a 11/16" X 16 helicoil.

Never thought about the size as I just go see my guy and get the size I need for SBCs. If all else fails, 3/4 16 tpi tap and bolt also exists so just taping to the next larger size my make it alright. Otherwise 3/4 - 16 Helicoil.

Bob

52-fan
03-01-2012, 10:42 PM
Never thought about the size as I just go see my guy and get the size I need for SBCs. If all else fails, 3/4 16 tpi tap and bolt also exists so just taping to the next larger size my make it alright. Otherwise 3/4 - 16 Helicoil.

Bob

Something to consider. Thanks. Maybe we can save it.

Alan
03-02-2012, 12:07 PM
SBC is 7/16" X 20

sweetolbob
03-02-2012, 12:53 PM
SBC is 7/16" X 20

Correct and as I said I've never found a stripped bolt in an SBC that there was not a helicoil available for so it never entered my mind that there was no 11/16 X 16, but the 11/16 and 3/4 NF are both 16 tpi which may allow the threads to be saved by going to the next sized tap (3/4). If not the only other way I know of to save the crank is a bigger and available helicoil or similiar thread restoration method.

Bob

nvonada
03-02-2012, 01:15 PM
I tried to do the same thing putting the pulley back on my Champion 6. I thought the pulley was not on all the way so I decided an impact wrench was just the ticket. I was very stupid. But the bolt broke without damaging the crank threads.
http://stude.vonadatech.com/images/Engine%20Pull/small/VT_20090525_3905.JPG
I can't imagine the crank is stripped unless the threads were crossed or rusted before. Either way I am sure a machine shop could heli-coil it.