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1969 Mustang Convertible 302 T5
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Discussion Starter #1
Just off of an out-of-car motor refresh and now my Thompson style pump has a leak. I've pulled the pump and I'm going to try a gasket update and repaint. While cleaning the bracket that came off the can (not the water pump), I noticed that the threaded adjusted hole looks suspect. I want to chase the threads but I can't tell what the threads should be. I was guessing 7/16" - 14, but it only threads partially and I don't want to wreck it. The bolt appears to be a 7/16" - 14 as well but when I tried chasing those threads, again, it felt like something is wrong. The threads on the bolt do not look right and I don't know if it is even the original or correct bolt.

What should the thread size be for the adjusting bolt on this Thompson style pump?
737971
 

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I believe the C7AA Aluminum bracket as displayed, used a 3/8" bolt in all positions. The 7/16" bolt was used in the 70 and newer steel cradle brackets in the adjustment hole only.
So--If yours has a 7/16" bolt it has been caressed.
 

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1969 Mustang Convertible 302 T5
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Discussion Starter #3
Lol. I had to laugh hard at "caressed". I've been known to caress bolts over my life - not necessarily on purpose. I guess I could just finish tapping the hole at 7/16" and see how it feels. Do you have any opinion on the aftermarket bracket (i.e. Scott Drake or whatever CJ Pony has)? I know I've read a couple negative reviews regarding the casting but to be fair, my OEM piece isn't exactly a work of art. I would just need to be assured it will fit because I really don't enjoy removing and installing pulleys on these things.
 

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1969 Mustang Convertible 302 T5
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Discussion Starter #5
Meh... I think I figured this out. I believe the bolt is an M10. The threads seemed buggered to me but that's probably because it was never worked all the way through when the pump was mounted on motor. It's tight (test fitting off of pump) but now I'm thinking that maybe I should just retap cleanly to the M10 threads and find a clean bolt. Obviously 3/8" is history for this bracket.

I know I'm making a mess of this but I do want to try and salvage the bracket. Nonetheless, I guess I'm glad I discovered the caressed bolt now and not after the pump starts throwing belts.
 

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Put a heli coil in it, As long as it’s not way wallowed out a 3/8 heli coil or kingsert should do the trick.
 

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1969 Mustang Convertible 302 T5
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Discussion Starter #7
Heli Coil. Excellent idea. I've never had to do a thread repair and with this out of the car it should be fairly easy. If it is done correctly, I've read that thread inserts are very reliable. Thanks!
 
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