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Hello Pontiac flathead experts:

 

I’m trying to get a 1937 Pontiac 2-door touring sedan with a 6-cylinder running again. To the best of my knowledge, it last ran in 1968. 
 

I’ve re-done the front brakes including new front brake lines and wheel cylinders and master cylinder, before moving to the back, I thought I’d deal with the fuel system. In particular, I’m speaking about the fittings that go in and out of the fuel pump and into the carburetor. I expected those to be flared fittings, but it appears as it the tubing is straight, not flared, and must get slightly compressed by the tapered seat on the male and female sections of the fitting. 
 

What are those fittings called?  Is there a supplier you prefer for replacement fittings?

 

Thanks for your consideration. 
 

Johb

 

 

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Posted (edited)

If you speak of what I think you speak of, the fittings are called "threaded sleeve". I bought some at Blackhawk Supply online 2 or 3 years ago, so I would try there. These fittings have a taper, and go on the tubing with no flare. Once tightened, the nut digs into the tubing and becomes part of it. 

 

https://blackhawksupply.com/collections/plumbing-brass-fittings-double-compression

 

My Pontiac is a 1936 Master Six, and my fuel lines were all butchered. Frankly I had a hard time figuring it out. Midland Metals is the maker of the fittings I bought from Blackhawk. I recently heard Eaton also makes them.

 

You can get the sleeve nuts, and also the female fittings that adapt to pipe thread. The right angle fitting is no longer made in 5/16" (and the sizes they do make don't look like the old ones). If your car uses a right angle fitting and it is missing, that will have to come from a swap meet or something. My 36 uses one at the carb. The tubing is ordinary 5/16" Bundyflex brake line.

 

On my 1936, originally, the tubing coming from the body originally had a "threaded sleeve" nut on the tubing, and that went to a female fitting on a rubber hose. The other end of the rubber hose had a piece of tubing crimped on and there was a another sleeve nut on that. It screwed into a straight female adapter (to pipe thread), and the pipe thread screwed into the fuel pump.

 

On the outlet side of the fuel pump was another straight female adapter. On the carb was a right angle female adapter. A piece of tubing with two sleeve nuts ran in-between.

 

I think your car was probably set up the same way in 37.

 

brass-compression-tube-fittings-nuts-dou

Note: In the pic below, there is just a clamped hose on the inlet side rather than the original setup.

 

45RJoGk.jpg

 

The original inlet hose would probably be about like this one. There would be another sleeve nut at the left and a female adapter to connect the left end to the fuel pump.

 

n4Utf1S.jpg

 

Edited by Bloo (see edit history)
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Bloo:

 

Thank you for your quick and informative response. I just place an order from Blackhawk Supply for these Midland double compression parts. In fact, I found that Midland now appears to manufacture a 5/16” elbow that is nicely rounded like the original rather than the “square block” style that you mentioned. I think the Midland part number for the elbow that accommodates 5/16” tubing and 1/8” NPT is Midland 16131. Blackhawk Supply claims that they carry it. While is is pricier than the compression nuts and straight adapters ($12.50 instead of $2-3), it looks as if that is an option. 
 

I trust that I should use a bit of Teflon tape or pipe dope on the 1/8” NPT fitting to get a good seal. 
 

Thanks again for you quick and informative response. 
 

John

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Posted (edited)

Wow thanks. I looked all over for the right angle fitting when I fixed mine. IIRC I had to buy a used carburetor to get one....

 

It's best not to use teflon tape on the pipe thread because a sliver could get loose and get in the carburetor. I either use nothing or  teflon pipe dope. Teflon dope is slippery so don't overtighten.

 

The threaded sleeves on the other hand don't need sealer but will need fairly heavy tightening the first time you use them, when they bite into the tubing.

 

Edited by Bloo (see edit history)
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