Help making a temporary Model A Tillotson Carb fuel line

A

akersa

Junior Member
I am getting ready to get my Model A running with a temporary fuel tank (the body is off) and I am trying to figure out what I can put together to make a temporary fuel line. I know that my carb has 1/2" 20 threads per inch female threads, and I was able to get a 5/16" line nut for brakes at a local parts store. Should I put a ferrule on the 5/16" line? I have experimented with trying to make a double flare fitting, but that doesn't seem like it wants to seal. I have an old carb that I was using and its threads are buggered up and I was able to get a plastic thread to barb fitting to thread in and hold tight enough to get the engine running and adjusted, but now that I am wanting to actually move the Model A under its own power down the drive way and around to make sure brakes and clutch are all working well I wanted to put something on it better than a plastic barb cross threaded in.

Thanks in advance.

I am really hoping to take it out for its first trip under its own power this weekend.

Adam Akers
 
Discussion of Brake Line Nuts at http://www.fedhillusa.com/?page=tech2.

I don't think you're headed to brake line, except possibly to use the tubing with a compression fitting. Brakes are normally done "double flare" and come prepared, or you have to mess with a specialized tool to make the double.

Scratch the brake tube - comes standard in 3/16 or 1/4.

VERY surprised you're at 1/2-20 for the thread. Are you sure? That would be SAE bolting, but doesn't include any taper for sealing.

1/4" pipe thread is 0.540 diameter x 18tpi. So you're not that.

5/16" compression tube fitting appears close. 1/2-20 thread. So maybe not so surprised.

I would take a guess and you want a 5/16 tube (larger than Model A fuel line which is 1/4" seamed tube) and a male compression fitting - and a compression ring. https://cloudfront.zoro.com/img/zoro_tips/compression_fittings_eZtip.pdf

An O-ring might work for temporary - but check you have enough compression so the tube doesn't inadvertently "walk" out of the fitting.

Copper tube is normally not recommended for gas lines - but for short service and sufficient "give" in a loop or two (think when you set up your still to make the moonshine) you can probably make it work for temporary.

Joe K
 
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Yes I am sure it is 1/2" 20 that is the same as a fine thread 1/2" bolt. It is not tapered thread so it is relying on the inverse flare to seat in the carb. The picture that Bob C put up looks like the brake line nuts that I have and I have Ferrules that fit the 5/16" copper tubing. I might just have to make that work. I was hoping that I just wasn't thinking of something and that there was a hardware store solution out there that I hadn't come up with yet.
 
A correction on my earlier entry. Bob C is correct in that the male fittings he shows are for the Model A - and the female hole they fit on the fuel filter and the Zenith Carburetor are 1/2-20 thread. But the male fuel line fittings made for the Model A are not standard compression male nuts. (see chart https://cloudfront.zoro.com/img/zoro...ings_eZtip.pdf)

Rather the Model A fittings are made to 5/16" fitting dimensions - but for the Model A application the hole (and matching compression ring) is 1/4"

I first thought you might use EITHER the standard 5/16" fitting OR the 1/4" "Special" Model A fitting - but I imagine the carburetor body is made specifically for the Model A Fitting to get that axial matching and opposing ring compression - so you may be limited to Bob's suggestion.

Interesting. I have used Model A Fuel line fittings for years - including the not-so-hot "integral shearing compression ring" variant - but never intellectually grabbed the fact that it is something special.

There - I've learned my something new for today. Now I can go to bed confirmed that today was not a waste.

Good luck. Keep it running...

Joe K
 
Thanks for the responses. Looks like I will just have to be patient and wait for my parts to arrive. With the 5/16 brake line nut I was able to get a piece of 5/16 copper and try with a ferrule, but as you said the taper on the ferrule did not match that of the carb, and since the carb is an allow I did not want to tighten it down to the point that it would start squeezing in know that most likely all I would end up with is a carb with stripped threads on the fuel inlet.
 
similar question, I had a warped Tillotson and just replaced it with a new one. The fuel line looked ok, so I didn't purchase one, but it seems that the ferrule on the side that goes into the carb is too far away from the end of the line - based on lining it up with a ruler there's about 5/16" from the edge of the ferrule to the end of the line. I can cut the excess with a pipe cutter, but does anyone know how far from the end of the line the ferrule should be? I've seen 3/16" or 1/8". Not sure it matters?
 
davisae130 said:
similar question, I had a warped Tillotson and just replaced it with a new one. The fuel line looked ok, so I didn't purchase one, but it seems that the ferrule on the side that goes into the carb is too far away from the end of the line - based on lining it up with a ruler there's about 5/16" from the edge of the ferrule to the end of the line. I can cut the excess with a pipe cutter, but does anyone know how far from the end of the line the ferrule should be? I've seen 3/16" or 1/8". Not sure it matters?
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It does matter. 1/8" is fine. I doubt you could use a tube cutter. A small fine blade hack saw or just a file if the ferrule is too tight to move.
 
Ford used a lot of different fittings for fuel systems back in the prewar and immediate post war eras. With the cost of a complete new fuel line from the vendors, a person can cut the old line and use it for rubber hose connects. Just make sure and use NEW reinforced synthetic rubber fuel line and it will last quite a while without worry. Rubber deteriorates so it's not the best long term material but I've had it last for over a decade on some of my motorcycles and they came new with 1/4" rubber fuel line.

The ferrule type 1/2"-20 fuel fittings are best fit by using a brass or steel female compression fitting to seat the ferrule fully before using it in an old Tillotson zinc casting. It will save the threads in there for longer duration. On a Zenith, with it's cast iron body, it's no problem.
 
Patrick L. said:
It does matter. 1/8" is fine. I doubt you could use a tube cutter. A small fine blade hack saw or just a file if the ferrule is too tight to move.
Click to expand...

After cutting w/a hacksaw be sure to de-burr the end of the line, both inside and outside.
 
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