New oil pressure switch doesn’t fit...318 LA

Righty Tighty said

I’ve never gotten bad advice from you, so what do you have in mind? I could find the tap I used to chase the threads and find an adapter that’s the same? I honestly don’t think anything I found would be much different than what I have currently though.

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Yes, that is what I am thinking of. What concerns me is the 1/8" NPT thread pitch is 27 tpi.....The only thing close to the thread ID that you said you measured is 1/2" coarse thread.. which is 13 TPI. But I am just guessing on that size based on your number' finding the tap would be best for sure. Do you remember if you were cleaning some other holes with that same tap? We could go from that

So if you tapped it for that, then you may have 2 thread pitches crossing each other. The new 1/8" NPT adapter may just be hanging the top 1-2 threads left in the original tapped hole if the straight tap was run down through there. Boy, this is a challenge....

Thread repair compounds would be more suitable in some way, but IDK how well that would work with the top thread or 2 still apparently begin so intact. With that adapter, maybe JB Metal Weld would have been the way to go... take off the paint around there, and use JB to make that new adapter essentially part of the block. That is the best/easiest I can think of....