Stripped crankshaft hole with new harmonic balancer bolt.

[dkraven]

Easy job into nightmare. Have the balancer pressed on with the correct tool, brand new bolt all the way in, ready to torque it down. Have my son use an old v belt to hold the pulley/balancer against the torque, go to torque it, and the bolt pops and spins. Here's where I drank a big glass of stupid... I figured the balancer must not be bottomed out and I kept spinning the bolt. The pic below is the result.

The new oem bolt is 1/8 inch longer than the original, which I didn't think would be a problem, and it stripped the hell out of my crankshaft. Why do they sell a bolt longer than the original and say it fits? I'm frankly as furious at Mr. Gasket as myself.

Anyways. now what the hell do I do? I've rrad about retapping the crankshaft for a big block bolt, is that the play? What do I need to know and think about?

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[MarineOne]

Had this exact thing happen and went up to the big block bolt. It's been this way for 10 years now

 

[dkraven]

What about just tapping it for the same 7/16 20 thread it is? I saw one guy on youtube do that and it worked. Guess if there's enough metal to "heal" the thread?

 

[Rustisbest]

Should be enough material there to go metric also. 12mm

 

[dkraven]

Should be enough material there to go metric also. 12mm

Interesting, what's the benefit?

 

[Rustisbest]

Interesting, what's the benefit?

It's smaller than the BBC bolt which is 1/2-20. Probably wouldnt have to drill it out any.
I've just ran the tap in there on stripped exhaust manifold bolts when I couldn't get a drill into position.

 

[PrairieDrifter]

Did you have the proper washer?

 

[dkraven]

Have the proper washer, even checked its size. Tried tapping it for the same size but the bolt still slipped. Currently waiting for the helicoil set to arrive and going to try that as a solution.

 

[Rusty Nail]

Good luck.

 

[GTX63]

Interesting, what's the benefit?

It gives you an additional option/chance.
First, retap for the same size bolt. You have nothing to lose.
If that fails then tap for metric; that gives you a second option and leaves a BB bolt for your safety net.

 

[Rusty Nail]

Plus you don't have to take the crank out of the engine...lol.

 

[KnuckleBuster]

Did the bolt bottom out in the hole? It doesn't look like it did. Are there any threads left in the hole? I wouldn't think an 1/8" would be a killer but can't say for sure.
If it comes down to repair, just HeliCoil it. Not hard to do, once you've made some working room.
Once repaired, this would be a good excuse to get a balancer installer. I know a lot of people do (mostly lucky people), but NEVER use an impact to install a balancer.
Good luck to ya.

 

[SquareRoot]

Have the balancer pressed on with the correct tool, brand new bolt all the way in, ready to torque it down.

So you used a balancer install tool? That should have seated the balancer. I'm not sure I have ever installed the washer and bolt. I'm not sure how it does anything if the balancer is press fit on the snout. I wouldn't worry about it, you don't need threads to get the balancer off. It won't matter until you install the balancer the next time. Maybe I'm crazy?

 

[MarineOne]

So you used a balancer install tool? That should have seated the balancer. I'm not sure I have ever installed the washer and bolt. I'm not sure how it does anything if the balancer is press fit on the snout. I wouldn't worry about it, you don't need threads to get the balancer off. It won't matter until you install the balancer the next time. Maybe I'm crazy?

They can fall off. Rare but happens the old 307 didn't come with one from factory

 

[dkraven]

Helicoil did the trick!

Was a tense hour as I left the harmonic balancer on the crankshaft while drilling and tapping to fit the coils. Cramped and hard to see, worried the whole time I was going to overcut the hole, but the bolt went right in afterward! Had my son use an old v belt with a crowbar to keep the pulley still while I torqued down the harmonic balancer bolt. Small victory with so much left to do on the truck but hell, I'll take it!