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

d55dave said
What about the rest of the pipe threads in the block, did you chase them too?

There is no way that I would trust that. Not only due to the potential for leaks, but also the very real possibility that it could, with temperature and vibration, blow the sender right out..... on the highway or at the top end of the track and empty the contents of your oil pan in a hurry, oil under the back tires, engine run dry, you get the picture.

You have two options that I can see. Number one, stuff something down in the hole to plug it and drill and tap to the next PIPE size, then use an adapter bushing, or figure out exactly what thread you cut, make sure the thread is in decent shape and use a straight thread fitting with an o ring or crush gasket to adapt it to pipe thread.

FYI, i don't believe that your pipe dope will harden as you expect. It is meant to remain soft and pliable.

When I replaced the core plugs, I didn't chase the threads since they were already in excellent condition. Those are the only other threaded holes I can think of that would be pipe threads, is that it?The only other threads I can remember chasing were for fasteners.

And you're right - the sealant I used didn't harden like I was expecting. The consistency is just that, like pipe dope. I did pull and wiggle on it quite hard (knuckles turned white and face turned red) for a good amount of time, even twisted/pulled and tried to unthread it, not a single budge. I get that under different circumstances (heat and vibration), it could behave differently. Re-tapping it is going to be my very last resort, as the engine is assembled and I don't want to drop any debris into the oil galley, even if I do stuff something in to plug the hole.

nm9stheham said
Once the sealer/locker is set, then do this for a test: Pull up hard and steady on the adapter a sender with 25-30 lbs force and hold it as long as you can; wiggle it when holding with this force. The actual force exerted on the adapter is gonna be about 15-20 lbs peak with max oil pressure.