Technical Model T Gas Cap Thread Size

A friend of mine has a repo Model T gas tank which currently has a bung type screw in cap. The cap almost looks like a barrel bung you would find on the top of a barrel. He would like to add a filler neck with a vent. Does anyone know the thread type, size and threads per inch. He says threads look fine. Does anyone know of off the shelf filler neck. He’s not local to me or I would measure with thread gage. Thanks in advance I’m sure someone has answer off the top of their head.

 

Bore out a stock brass T gas cap , & silver solder a neck into it .

 

BTT

 

I have a Moon aluminum flip the lip cap on my car that screwed on. No idea as to the threads. Bought it back when Dean Moon was still alive.

 

It's 2 - 1/4" 14 threads per inch.

 

Is that straight threads or tapered pipe threads? Thanks, knew someone here would have an answer.

 

Straight pipe I believe. I used to sell a hose adapter for Model T tanks.

 

Ask the Model T Club of America. They're very knowledgeable.

 

I found a thread where the MTFCA is discussing the subject, their answers are all over the place.

But the best answer was to buy a new cap, cut a hole in it, and braze it to the end of the filler neck you're making.

I personally would probably do some measuring, and make threads that fit using a lathe.