Anyone have any issues using a heli-coil in a crankshaft for a flexplate bolt? I have no idea how it happened, just got the motor back from freshening and dyno time and 1 of the bolt holes in the crank had the threads galled and messed up, tried a thread chaser with no luck, made a little jig to run a tap through and caught the good threads and it cleaned up and the bolt runs through it smooth now but it definitely feels looser than the others, I put loctite on the bolt and it feels like it's pulling the threads, I stopped at 60 ft.lbs., all the others tightened to 85 as normal, I'd hate to screw something up over a $5.00 bolt

I think it's one of those, what do you have to lose situations.

I would have zero problems running a Heli-coil in it. If it worries you about screwing in the bolt you can use a short stud and Loc-tite it in. They make Heli-coils specifically for using a stud also. I realize that is a short stud but it's just something to consider. Usually a Heli-coil is about as strong as the original base metal. There is some pretty good info in this document.

https://www.stanleyengineeredf...c-2000_rev11_web.pdf

I think I would feel better about using a heli-coil, than an under-tightened bolt with limited threads.

If it's a chevy I think I would take it out 1/2-20.

A properly installed Heli-Coil is as good or better than the original thread.

Look at a time sert instead but I would do either over a screwed up threads

You can re-tap it to 12mm and just use a metric bolt in that hole

quote:

Originally posted by 1leg:
If it's a chevy I think I would take it out 1/2-20.

This

it seems the helicoil would be the best choice you could still go bigger later if needed

I can't see drilling and tapping oversize making it a ba$tard when repairing it to stock size is a viable method?

thats what i was trying to say curtis lol

quote:

Originally posted by rusty:
thats what i was trying to say curtis lol

Great minds. LOL

Could just cover the threads in JB weld, torque it to 60lbs and send it. Bet its stays put until the next time you pull the engine.

quote:

Originally posted by Big Steve:
Could just cover the threads in JB weld, torque it to 60lbs and send it. Bet its stays put until the next time you pull the engine.

Does it really need all the bolts?

quote:

Originally posted by CURTIS REED:
I can't see drilling and tapping oversize making it a ba$tard when repairing it to stock size is a viable method?

If the crank is out of the engine and can be mounted in a mill or at the very least a good drill press then by all means repair with an insert of some sort....but if you're laying under the car in the middle of your driveway or the pits, a 12mm tap will follow the correct angle of a striped out 7/16 hole....it's a quick, fairly accurate repair that holds. You can always drill and tap for an insert next time you take the engine apart...or really "ba$tardize" it and drill and tap all the holes to 1/2"...