Sealing threads on fuel line connections

[banc123]

I put on a new carb and used the fuel line that came with it. Also put on a new inline filter, but the new carb came with a connection adapter that has a little screen built in it. I'd rather use the new hook up than the old one I think. However the new one has male threads that go into the carb and female threads to connect to that go straight out. I need a 90 to go back to the fuel tank. I was able to find a 90 with male threads on both ends so the one end threads right into the adapter with the screen that came with the carb leaving male threads pointed back to the fuel tank. All the barb connectors had male threads as well so I have a long female threaded connector with threads all the way through it to connect the barb.

Does the trick but I have the feeling it could leak around the threads.

Is there a fuel approved thread sealer ? I'd think the teflon tape around the threads would get eaten up by the fuel.

 

[skipmarcy]

No, teflon tape works just dandy with gasoline, have used it for over 40 years professionally.

 

[Soundguy]

It would be AWESOME to know what machine this is on.

if something like an N series, you can buy the lil carb elbow with screen and 90' bend with male/female threads for a couple bucks at tractor supply.

while white tef tape will work on connections that use threads to seal.. I hate tape in fuel applications.. a single thread of tape can come off and block a carb passage.. and that teflon will be nigh impossible to remove with carb cleaner. there are paste type sealers like gasoila that are great for fuel connection, or oil.. etc. if you have to use tape on something, there are yellow tef tapes made for fuel setups. still.. I doubt you will be needing any sealer if you use the correct connections.

soundguy

I put on a new carb and used the fuel line that came with it. Also put on a new inline filter, but the new carb came with a connection adapter that has a little screen built in it. I'd rather use the new hook up than the old one I think. However the new one has male threads that go into the carb and female threads to connect to that go straight out. I need a 90 to go back to the fuel tank. I was able to find a 90 with male threads on both ends so the one end threads right into the adapter with the screen that came with the carb leaving male threads pointed back to the fuel tank. All the barb connectors had male threads as well so I have a long female threaded connector with threads all the way through it to connect the barb.

Does the trick but I have the feeling it could leak around the threads.

Is there a fuel approved thread sealer ? I'd think the teflon tape around the threads would get eaten up by the fuel.

 

[banc123]

Its a new Zenith carb on a pre 75 Ford 3000

The carb came with a screw in straight female threaded connection with a screen that screws in the carb side, it leaves female threads to connect to.

I found a 3/8 brass 90 at lowes and a way to use brass connectors to get to a brass barb connection to attach to the 5/16 fuel hose.

I think those are designed to have a thread sealer. When I tighten it all up and block the end that goes into the carb and blow into it, I can feel air from the joints. Very faint, but pretty sure those threads are designed to be sealed.

 

[Soundguy]

taper threads need no sealant.. straight threads neaed sealant.. unless it's a special fitting made for flair or compression.

I'm not up on the 3 cyl gasser fuel system.. though originally it would have been a holley.

3000 was from 65 to 75

soundguy

 

[Mace Canute]

Why do people think taper threads never need sealant? For everyday common NPT - (National Pipe Thread Taper) - a sealant compound or Teflon tape must be used for a leak-free seal. It's only when you are dealing with NPTF - (Dryseal American National Standard Taper Pipe Thread) - that you don't need a sealant.

 

[Soundguy]

for much of the applications we are talking about right here in this thread about these carbs.. no sealent is generally needed on the types of fittings I mentioned.

soundguy

 

[Mace Canute]

The taper on NPT threads allows them to form a seal when torqued as the flanks of the threads compress against each other, as opposed to parallel/straight thread fittings or compression fittings in which the threads merely hold the pieces together and do not provide the seal. However a clearance remains between the crests and roots of the threads, resulting in a leakage around this spiral. This means that NPT fittings must be made leak free with the aid of thread seal tape or a thread sealant compound. (The use of tape or sealant will also help to limit corrosion on the threads, which otherwise can make future disassembly nearly impossible.)

There is also a semi-compatible variant called National Pipe Taper Fuel (NPTF) also called Dryseal American National Standard Taper Pipe Thread, defined by ANSI B1.20.3, designed to provide a more leak-free seal without the use of teflon tape or other sealant compound. NPTF threads are the same basic shape but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.

One needs sealant, the other doesn't (or shouldn't). A hardware store fitting, such as the 3/8 brass 90 banc123 said he bought at Lowes, is highly unlikely to have been made to NPTF specs, you're luck if is made to NPT specs...