Stripped thread on harmonic balancer - what do I do??

[OzCuda]

Bolting the crank pulley on went from an easy job to big screw up.     Was very careful not to over torque these bolts so must have been cross-threaded, either way I now have a hole where the thread used to be and I'm not sure what my best course of action is??

Compounding the problem is that the crank was a little worn so it was knurled to allow the balancer to be pressed on so I suspect that removing it for repair or replacement might loosen it up again meaning tearing down the now complete, installed engine to replace the crank. 

Need some good advice on this one, can this be fixed effectrvely on the car, either by fitting a helicoil to replace the thread, or using some sort of liquid metal to 'glue' the bolt in?  Impact of these solutions on the balancer?

[ShelbyDogg]

Use a helicoil and stay away from the liquid thread repair kits. Those Helicoils are good stuff.

Rob

[miketyler]

yup - so the threads are gone? Stripped threads on bolt and crank hole? Heli-coil is probably your only option, could be tough if its in the car. I would first try and retap to std and new bolt. If you get decent mesh, you could possibly put a thin stripe of Loctite on it and keep your fingers crossed. Of course, I would monitor it.

Is this a 340? I had the same issue with the neck on my engine. I had to have it knurled, then ground. Previous owner said the HB had a slight "orbit" and only needed the crank bolt tightened. (yeah, right) Maybe that's how your threads got boogered from overtightening trying to correct a wobble condition?       

[OzCuda]

Engine is a 383.  Bolts were new high tensile so it survived and is replaceable anyway, thread is pretty well gone so if tapping was the go then would have to go to a bigger bolt and then would have balance issues??

[miketyler]

I would think you want to keep the bolt size standard. You will need to slightly oversize and tap the crank snout for the heli-coil. I think the heli-coil kit comes with the matching tap for the helicoil. Am not sure but I think they are a special size, designed specifically for heli-coil. 

[ShelbyDogg]

Go to any good auto parts store with your bolt and get the right helicoil kitfor that size. Then  go to a tool store and get the correct size drill bit  that the helicoil calls for.  Once you get it installed, the balance should be the same.  Quit wasting time thinking about it and just do it.

[67Vette427]

If you haven't tried tapping it I would. Take the radiator out if you have to for clearance if need be. Then tap it and spray it out with WD-40 and repeat that several times and see how clean it comes out. Just be sure you tap it straight and level. If it doesn't work them go with the heli-coil. Sometime even when they look real bad they clean up okay.Good Luck

[miketyler]

 

[ntstlgl1970]

Did you strip the hole in the crank that retains the balancer or a hole in the balancer that retains the crank pulley? I didn't get a clear image of what you are working with.

If the crank, you might have just pulled the first couple of threads, clean it up (if you can find a tap that size or buy another bolt and use that as a tap) as 67 427 said. If you tried to "pull" the balancer on the crank with the bolt, that's probably what happened. If it is worse, find someone with experience with helicoils to help out. Finding a drill bit, tap or helicoil kit to fit a 3/4" or whatever size thread that is may be a challenge, also having a drill to run that bit at the right speed may be tough as well.

If you stripped one of the bolt holes in the balancer, I would just drill and tap to the next size thread 3/8-16 or whatever.

[Autophile]

If only the first 10 mm or so of threads are stripped in the crank snout, then just clean the threads and buy a longer crank bolt. ARP makes longer crank bolts.

[OzCuda]

It was a thread in the balancer for one of the pulley bolts.  Bought a helicoil kit today and will try it on the weekend.  Thanks for the advice, I'll let everyone know how it goes.

[gkring]

Bad pulley bolt to balancer? No big deal. I would not even freak if you left it off all together. 5 out of 6 bolts will do the job, of course all 6 would be better. Should be abe to drill and tap the balancer pretty easily with a helicoil kit. Don't worry about the balance. I think we were all afraid it was the big bolt holding the balancer onto the crankshaft which is alot more critical. I'd helicoil it, but would not stop driving the car.

[OzCuda]

Well, its all fixed.  Ex Aircraft mechanic brother came over and gave me a hand (read - did it for me) to heli-coil it.  Two of the holes were actually stripped so was worth getting the kit.

[miketyler]

Bad pulley bolt to balancer? No big deal.

Yup - I thought this was the crank bolt hole. Good to hear you got her all fixed up