Fitting for Carter W-1 Climatic Choke?

[jdshott]

I have a 1937 Pontiac that uses the Carter W-1 352S carburetor with a Climatic automatic choke. There is a short 0.25" diameter tube that connects the exhaust manifold to the threaded zinc of the choke housing.  My existing carburetor attaches that tube to the choke housing with a brass-ferruled compression fitting.  I think that is the wrong fitting.  Does anyone know what is the proper nut and bushing or washer to attach this tube to the choke?

 

I have attached three photos.

 

The first is a close up of the threaded zinc choke housing.  I believe that is a 7/16"-24 thread.  You can see that the threaded portion of the zinc housing is somewhat damaged due to the nut/ferrule combination that was used.

 

 

The second is looking into the choke housing where this tube would fit.  It is approximately 0.255" in diameter with no significant tapering to compress a conventional ferrule.

 

 

The third picture is of the nut and ferrule that I took of this carburetor.  In particular, the ferrule takes up so much space, that the nut barely engages on the threaded zinc housing with even a full single turn of the nut.

 

 

If anyone knows what type of nut and bushing/washer should be used for this application, I would greatly appreciate your input.  If I were looking at this as a plumbing problem, I would think of using a tapered washer and nut similar to what is used on the stem of a multi-turn stop valve.

 

Thank you for your consideration,

 

John

Edited February 11, 2021 by jdshott
Minor correction (see edit history)

[Bloo]

What you have is what I would expect to see. I don't know why it is only catching one thread.

[carbking]

What you show is what was/is used.

 

Yes, it can be problematic.

 

A little corrosion on the zinc threads, an impatient "mechanic" and the fitting is cross-threaded.

 

Have seen many choke housings that were damaged. Different "fixes" can be tried: rethreading the end with a die, cutting off the end if too much metal has been removed, then rethreading, there even used to be a brass fitting that could be screwed into the zinc (self-tapping threads) with new threads for the regular fitting. This fitting repair was the darling of some of the least expensive commercial carburetor rebuilders, and was generally good for one time use, then totally ruining the choke housing beyond repair.

 

Yours looks like there is sufficient metal left to cut off the end, and touch up the threads.

 

Jon

[jdshott]

Thank you both for your help.  I will get a proper die, chase the threads carefully, and then re-assemble even more carefully.  Thank you again for your expertise!  I didn't want to rush ahead and make a mistake ...

 

Stay safe!

 

John