Crank bolt to hold damper

RustyRatRod said

I wouldn't hesitate to helicoil that thing and run heck out of it. It's arguably stronger when done correctly. Much like a cylinder sleeve.

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It's not the pullout thread strength that is the issue here RRR... it is the extra thread in the way of the vibration path to the damper that is the concern. How energy may, or may not, concentrate in the helicoil that can cause new fretting at the inner or outer threads of the helicoil, is a total unknown for a damped crank like this. I suppose you could try it, and indeed it might not be a problem, but it is not as simple a situation as it may appear. And if it is not a crank system that uses a damper, then the vibrations are not an issues.

Remember, without the damper, the crank is very much subject to breaking from the torsional vibration energy. I don't think everyone understands the high frequency torsional vibration that occurs here, and the level of energy that can be involved. It is not at all the vibration we feel from a crank imbalance; it is typically at a frequency of 6000 to 8000 cycles per second for cranks of this size range.