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KFunk

Re-threading a crank bolt.... Yea or Nay?

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Let's say you have two nearly identical crank bolts, except one has SAE threads and the other has slightly different metric threads.

The SAE one will start to thread into the crank, but binds up. Would it be wrong to run a re-threading die down the crank bolt and make them closer to metric? Think it'll hold on there? I might add red loc-tite for the hell of it.

This is so I can use a hand crank bolt from an MGA engine, on my truck's nearly identical 1300 that has a few metric threads in odd places, and the original hand crank bolt is NLA. I've got the hand crank and can't wait to try starting it that way, but somebody swapped the engine to a slightly different one that just has a regular crank bolt.

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No

find one

Fine CD, I'll do it the right way. I bought a Datsun crank bolt...

(Nah, not really my first choice. I tried re-threading the MGA bolt, but still ended up with the wrong threads due to a bad measurement of the original bolt)

Then I was browsing ebay and found a set of pulleys and hand crank bolt for a Datsun 1500 roadster. I asked the seller if he could split up the stuff and just send me the bolt, so I took a chance on hoping it was the right thread. It threaded in perfect, and torqued down fine (after havign to buy a monster 1 1/2" socket, and moving the radiator to fit the big socket in there.

But it works! If the truck has been warmed up, it barely takes a half spin on the crank, and she's a running. Almost no drama at all.

But.... if it's sat for a few hours, and you try, and it doesn't fire on that first half crank, she kicks like a mule if I try to keep cranking into the next compression stroke. It can be a little... violent.

Following all safety precautions of course, thumbs and fingers on the same side of the crank (so you can easily let go and let her fly), and pulling toward yourself (so you're not putting shoulder toward it and risking a broken shoulder if it snaps back).

I'm still not sure how it can snap back exactly, since the crank bolt makes it so that it can go only one way (the pins would just slide up 'ramps' to push it outward). But still, it must just be the sudden stop in a compression cycle.

Not sure if I'll be able to overcome that if its cold. Maybe it'll be better when the warmer weather comes around...

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