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Crankshaft Repair- Helicoil? Help!


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so some how tonight i managed to screw up the treads in the crankshaft on my contours new engine... pulled the pulley off and replaced the seal went to install the pulley again and it seemed like the bolt was going in fine, i was wrong, threads are screwed... i went to pull the bolt back out to put a dab of rtv on the keyway notch like the factory had it and noticed the bolt wouldnt go back in again easily. I am going to try to get a tap tomorrow and see if that will be enought but i am expecting the worse... anyone ever heli-coiled a crank pulley bolt hole? the bolt was damaged too but i took the bolt from the old engine to use. any insight would be great

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a friend just suggested to me that i could possibly run a larger tap through it and get a new bolt, any thoughts on that?

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a friend just suggested to me that i could possibly run a larger tap through it and get a new bolt, any thoughts on that?

How is the engine balanced, internally or externally (like the 302?)

If you run a bigger tap through, you're probably going to have to drill out the flywheel to fit the larger bolt and that just sounds messy.

Whatever you do, I'd be tempted to say do it to all 6, as not to effect the balance of the crankshaft. 8 grams ain't a big deal until you're at 7000RPM...

Ian

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This is on the front of the engine... For the damper/serp pulley bolt.

:homer: Completely misunderstood your post.

Did you pull out metal or just cross-thread it? I.e., will a chase with a tap and a good smear of red Loctite seal it up?

Is the motor in the car or still on a stand? If it's easy, I'd say just throw a helicoil in there. If inserts are holding up my spark plugs, a buddy's carburetor, and another buddy's brake calipers... A Helicoil's probably safe for your crankshaft. Those dampener bolts aren't exactly a grade 5, I would imagine... Best stick with the original.

Just my $0.02.

Ian

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If you can get a drill to it, go with the helicoil. Those things are great. At work we use helicoils on all out aluminum threaded holes. The helicoils are steel and hold up much better than aluminum. Just be sure after you install the coil that you make sure you pop the thread tab out of the bottom and see it isnt left in the motor.

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well tap and die seemed to have done the trick, i have not torqued it down yet but it threaded in nice and smooth and easy. the engine is on the floor (well attached to my engine hoist) so it is pretty easy to see whats going on and such. if i did happed to replace it, it would get a bolt of the same grade or higher, being metric the current bolt is a 10.8, oddly enough it has the exact same thread pitch an diameter as a lug stud. i have used heli-coils before (on a chevy 350s timing cover bolt holes) just wasnt sure if it could be dont to a crank...

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If the tap cleaned up the threads, you should be fine. Use blue loctite on the bolt. I believe the pulley bolt is TTY, but I've always reused them without trouble.

I think it would be kinda difficult to helicoil the crank bolt. The crank is forged and would be tough to drill and rethread by hand.

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