302 oil sending hole thread

[fireZ]

Anyone know what the thread is were the oil sending unit threads into on a 302 engine? I am trying to clean the thread up before installing the sending unit. Thanks

[CNorton]

1/8th pipe.

[fireZ]

Thanks for the help but I think the owner previous me has run a 3/8 NF 24 down through the hole. Will a heli-coil fix this do you think?

[JohnZ]

Thanks for the help but I think the owner previous me has run a 3/8 NF 24 down through the hole. Will a heli-coil fix this do you think?

I'm not aware of a Heli-Coil that will adapt a straight machine thread to a tapered NPT thread, and there isn't much difference in the diameter of a 3/8" machine thread vs. a 1/8" NPT thread to make a typical bushing - not enough wall. You'll probably have to make a custom adapter fitting with a hole through it with 3/8"-24 male threads that screw into the block (and a square shoulder with a gasket to seal it) with a larger top section that has 1/8" NPT female threads to accept the stock adapter fitting. Maybe Jerry has seen this kind of butchery before and has another suggestion.

[fireZ]

Thanks John, I am very discouraged by what a so called machinist did to my block. I am going to talk to some other machine shops and see if I can get a adapter made to take care of this problem. I guess a matching 68 Z28 motor means nothing to some ,just another motor.

[CNorton]

There's a "mistake" that's a little more egregious than most.  Anyone who can't feel the difference between chasing a 1/8" pipe thread and cutting threads with a 3/8" machine tap may have made other mistakes as well.  Even the greenest apprentice should have noticed that something wasn't right with the situation.  It makes one wonder.

[fireZ]

I agree with you this guy had to know he was cutting material away. He contends it was already that way when he recieved the block. I am sick about the situation.

[JohnKY]

Can you drill it out, and re-tap with 1/4" NPT? Then, use a 1/4 X 1/8 bushing.

[fireZ]

Yes I think it will have to be drilled out and then basically sleeved before it is retapped

[fireZ]

I tried what John Z mentioned and it worked perfectly. It took a little work  to make the bushing with a male thread but in the end it worked. Another 68 Z motor saved for the original car, Thanks everyone