Crankshaft threads for balancer stripped!!! - Team Camaro Tech
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post #1 of 18 (permalink) Old Feb 20th, 10, 03:59 PM Thread Starter
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Steve
 
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Crankshaft threads for balancer stripped!!!

What would be the best method to repair the threads in my crankshaft that holds the harmonic balancer on. I was assembling my engine...turning it using the balancer bolt so I could adjust the valves and all of a sudden.....it broke loose. I just got this short block back from the machine shop with a "new" crankshaft installed. I'm sure he'll make good on the repair but I'd like to know the best method before I talk to him. I know about heli-coils, but what about drilling and tapping to the next larger size? Any ideas would be appreciated.
Thanks

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #2 of 18 (permalink) Old Feb 20th, 10, 04:48 PM
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Re: Crankshaft threads for balancer stripped!!!

It's not the engine builders fault. Your really not supposed to turn the engine by the balancer bolt. We've all done it though. You can buy a tool from Jegs or Summit that bolts on the front of the balancer. I'd just go one size larger.
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post #3 of 18 (permalink) Old Feb 20th, 10, 06:02 PM
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Re: Crankshaft threads for balancer stripped!!!

Steve,
I prefer a helicoil rather than going to the next size up. Like Todd said, the bolt really is not meant for turning the engine over but it really should be able to do it without stripping the threads

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1971 Chevelle "Heavy Chevy" original owner


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post #4 of 18 (permalink) Old Feb 20th, 10, 06:31 PM
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Re: Crankshaft threads for balancer stripped!!!

Here is the tool I was referring to. http://www.jegs.com/i/JEGS/555/80743/10002/-1
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post #5 of 18 (permalink) Old Feb 20th, 10, 06:39 PM
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Re: Crankshaft threads for balancer stripped!!!

Quote:
Originally Posted by BillK View Post
I prefer a helicoil rather than going to the next size up.
Why the helicoil over a larger bolt?

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post #6 of 18 (permalink) Old Feb 20th, 10, 06:48 PM
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Re: Crankshaft threads for balancer stripped!!!

Heli-coil is said to be stronger than the threads that were there to begin with.

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #7 of 18 (permalink) Old Feb 20th, 10, 07:07 PM Thread Starter
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Re: Crankshaft threads for balancer stripped!!!

I believe the heli-coil would be better so I can still use the normal puller and pusher to install/remove the balancer. I'm kinda miffed by the opinion to not use this bolt to rotate the crank as I've been doing this for years without incident. How do you guys rotate the crank to set up valve lash?

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #8 of 18 (permalink) Old Feb 20th, 10, 07:09 PM Thread Starter
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Re: Crankshaft threads for balancer stripped!!!

Oh my. I just looked at the tool that Todd refered to....never knew it existed...poop.

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #9 of 18 (permalink) Old Feb 20th, 10, 07:27 PM
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Re: Crankshaft threads for balancer stripped!!!

I also use both of these, when the balancer isn't installed yet. Use the right tools and you won't damage anything.
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post #10 of 18 (permalink) Old Feb 21st, 10, 06:09 AM
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Re: Crankshaft threads for balancer stripped!!!

So do you have to pull the balancer every time you run the valves? That bolt is torqued to 85 ft/lbs. As long as your motor turns with less force than that you will never hurt those threads.
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post #11 of 18 (permalink) Old Feb 21st, 10, 06:22 AM
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Re: Crankshaft threads for balancer stripped!!!

Taking the sparkplugs out (PITA) when turning the motor by hand at the crank makes things easier too

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #12 of 18 (permalink) Old Feb 21st, 10, 07:14 AM
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Re: Crankshaft threads for balancer stripped!!!

Quote:
Originally Posted by markw View Post
So do you have to pull the balancer every time you run the valves? That bolt is torqued to 85 ft/lbs. As long as your motor turns with less force than that you will never hurt those threads.
Not if you use the tool Todd listed; it works great. The other's work nice to, especially during the rebuild process.

Turning a fresh rebuild with a radical cam and probably with plugs in is just too risky. Using the tools saves a lot of trouble.
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post #13 of 18 (permalink) Old Feb 21st, 10, 07:47 AM
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Re: Crankshaft threads for balancer stripped!!!

Does that tool stay bolted to the balancer? Looks to be counterbored for the crank bolt. Neat idea.
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post #14 of 18 (permalink) Old Feb 21st, 10, 12:19 PM
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Re: Crankshaft threads for balancer stripped!!!

Quote:
Originally Posted by DOUG G View Post
Heli-coil is said to be stronger than the threads that were there to begin with.
but the heli coil is still threaded into the parent metal- which makes it as strong as a bigger bolt.. i think most small block people just drill and tap it out for a big block balancer bolt. if we are talking about a big block, then upgrade to a bolt used on any number of other engine families.

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
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post #15 of 18 (permalink) Old Feb 21st, 10, 01:16 PM Thread Starter
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Re: Crankshaft threads for balancer stripped!!!

Just to clarify my situation. The engine is on a stand and I did not have the spark plugs in and only half the valves were adjusted when the threads broke loose. The engine required 25 ft/lbs to turn before I even had the heads on....but I don't have any idea what a short block with new bearins and piston rings requires to turn. At any rate, I kind of agree with Mark that since the bolt is torqued to 85 ft/lbs., the threads should have held up. At any rate, you can bet in the future I'm gonna use one of the tools suggested even if I have to remove the crank pulley when it's in the car. Thank you all for your comments.

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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