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Damaged Crank Damper and Keyway Repair


Zmanco

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Some of you may remember that my crank damper came loose and damaged the keyway.

http://forums.hybridz.org/showthread.php?t=127217

 

Last weekend I finished the repair and after a few drives so far all is well. In brief, I followed the repair as suggested by the Miata guys: http://www.mx5.net/garage/hsue/LoctiteCrank1.html

 

Instead of loctite 242, I used 243 which is rated for exposure to oil. Also, I had to do a fair amount of filing of the crank around the keyway so the damper would fit over it. I bought some small files from HF and just went really slow to avoid taking off too much.

 

I ordered the longer crank bolt 12309-V0800 that Slownrusty had suggested, but the hole in my crank was not drilled far enough to use it. I didn't want to reuse the same one that had previously come loose, so I stole the one from the original L24.

 

If there's a lesson in this it's I wish I had used the loctite 243 on the crank bolt right from the start. Others had recommended it, but for some reason I didn't follow that advice. :bonk: As you might imagine, I would STRONGLY recommend that anyone who happens to have their damper off use loctite when reassembling it (use it both on the crank threads as well as between the damper and crank snout). I'm guessing that while I had R&R'd mine several times before with no issues, the last time I did was to install the new cam. I'm thinking that regular trips to 7k rpm may have been the issue this time.

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If there's a lesson in this it's I wish I had used the loctite 243 on the crank bolt right from the start. Others had recommended it, but for some reason I didn't follow that advice. :bonk: As you might imagine, I would STRONGLY recommend that anyone who happens to have their damper off use loctite when reassembling it (use it both on the crank threads as well as between the damper and crank snout). I'm guessing that while I had R&R'd mine several times before with no issues, the last time I did was to install the new cam. I'm thinking that regular trips to 7k rpm may have been the issue this time.

 

If you have the large front damper it won't hack 7K very well. The first signs of a problem are bits of rubber that look like they came from the fan belt on the bottom of the hood and up the inner fenders. That's the sign of a damper dieing, and you better take notice.

 

You also need to throw away the flywheel bolts and install new ones. When you lose one end of the crank the other takes all the beating. It may seem like overkill but you won't be very happy when the flywheel comes loose and wipes the end of the crank. Don't ask how I know this.

 

Cary

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i always thought that loctite wouldn't be efficient because of the torque required on the crank bolt... :hs:

It really doesn't matter. Loctite acts like a kind of a glue to give a bit of a vibration elasticity to the torque setting. It is especially important when the torque setting doesn't cause much elastic yielding on the bolt or other piece.

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