US D gas tank

[Mark Poss]

I need to clean up the threads on the kerosene bung on a 1930 D gas tank. Can someone tell me what tap I need. Thanks in advance, Mark

 

[HFP]

Most letter series are 3/8" pipe thread.

 

[Mark Poss]

Thank you

 

[Ray,IN]

You don't want to use a thread tap. Instead use a pipe thread restorer, it doesn't cut, it's made with 4-6 "corners", no flutes. You simply screw it into the threaded hole, being careful not to screw it in too deep; sneak up on the depth while testing it with the part that fits into the bung.
Using a standard thread-cutting tap simply cuts away any deformed thread. You want to reform the metal into the original thread
You don't need to spend the money to buy one, instead visit an AutoZone store and ask to borrow one. If they don't have it, they go buy it and lend it to you. The process is, you leave your CC number and if you don't return the item, you bought it; otherwise when it's returned they hand you back the paper with your CC number.