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Discussion Starter · #1 ·
Can anyone tell me what size bolts I need for a 302 water pump pulley? I have tried two sizes, one threads half-way on then gets stuck, and the next size smaller slides through without hitting the threads. Am I missing something? Could it be metric? Its a 68 style pump so I thought it should be standard. Help please! TIA
 

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If it starts and goes about half way then stops it is probably cross threaded. Try going the opposite way (counter clock-wise) for a few turns before turning it clock-wise at the beginning. That will align the threads better. If it starts at all, it is not metric.
 

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The fan-pump bolts are fine thread and if memory serves, they are 5/16 diameter, so they would be 5/16-24. Length will vary with your fan/pulley/spacer combo.
 

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Sounds like you're trying to force a coarse thread bolt, should be fine thread.
You may have screwed up the water pump threads with the coarse bolt.
Also don't use common harware store bolts!
 

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I struggled with this very thing yesterday. I don't know the size, but they are definitely fine threaded. Turns out it's pretty easy to cross-thread the pump. I had 3 that would thread through fairly easily, and 1 that will only go in about halfway. When I backed that one out, I could see metal shavings in the bolt threads. Hopefully your threads are still in good shape.
 

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Discussion Starter · #6 ·
Ok there is my problem. I knew I wasn't cross threading the bolts because it happened with each hole and i was being extremely careful. I was pretty sure it was 5/16 but I was using coarse thread. Makes sense, I should have tried fine thread. That never even crossed my mind. I was careful not to force anything so I think my threads should still be alright. Too bad I gotta wait a week to check. Thanks fellas!
 
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