fyne82

Hi All,
I just replaced the metal fuel line between the TBs with a new aluminum setup with a gauge to verify fuel pressure. I had a few leaks so I used Teflon tape (general tape blue roll). I used the littlest bit on the threads and it fixed the problem. Now I'm hearing/reading that was the wrong thing to do. I should have used tape or paste rated for gasoline. The tape I used said 'oil and chemicals'. Now I have to take it all apart in fear that the tape I used may deteriorate and break off and cause major issues down the line. Is the tape I used wrong? What's better tape or paste?

lars

The fuel lines are not pipe threads, so they do not seal on the threads - the lines have "inverted flare" connections, and the fuel pressure seals on the flared tube and the conical mating connection. By using teflon tape on the threads, all you did was provide lubrication on the threads so you were able to smoothly torque the fittings properly. You could have done the same thing with some light assembly lube on the threads. At this point, it's irrelevant what you have on the threads - your fittings are now torqued tight enough that the flares are seating and sealing - you are not sealing on the thread tape.

Lars

fyne82

You know Lars you got me thinking....when I took apart the connection where I was getting a leak the flared end and conical end didn't seem to be making a very 'true - squared up' connection. I loosed up some of the other joints and pulled it all back to were the leaking joint 'squared up' in the connection. I added the Teflon tape to the threads probably thinking that's why it was leaking and didn't think of the connection until you made light of it. I don't have any leaks for the 15 mins it was running and the short trip around the block.
Thanks for explaining it as you did, its making more sense now.

lars

Yes, it's very important that the inverted flare connections be assembled correctly with no misalignment or binding: The flared tube must seat squarely on the inverted flare "cone" in the mating fitting in order to seal. It's a good idea to fully seat the tube fittings by running the fittings all the way in with your fingers: If you cannot mate the fittings and thread them fully together with your fingers, you have misalignment that should be fixed. Never "pull" the fittings together using a wrench due to the fittings being "too tight." This is a sure indication of misalignment which will cause a leak. And, as noted, always apply a light lubricant to the threads of the fitting and to the back surfaces of the flared tube to eliminate any galling - this will assure proper torque. Good job getting it right!

Lars

fyne82

Then I got it right then. After loosening other joints and squaring everything up the parts and joints basically fell into place. I tightened everything by hand and gave it a quick 1/4 turn till it felt right. The tape I applied then probably didn't do anything then as you stated. I aint going back in to remove it. You can't see it and it aint leaking. That gives me time to do others things.

Thanks again!

lars

No point in removing the tape. As noted, the tape is simply acting as a thread lubricant and the fuel lines are actually sealing on the flared surfaces now, as they should. The tape and the threads will never be exposed to fuel, so you're in good shape. You did the right thing by loosening everything up to "relax" the tubes and get them properly aligned. You also did exactly the right thing by finger-tightening everything to assure the alignment, and then doing a final snug-down with your wrench. Nice work!

As a side note to this, a lot of the guys running the Tripower setups have a nightmare of a time getting all the fuel lines to stop leaking. The aftermarket reproduction fuel lines look very nice, but the bends and angles are not perfect. People installing all these lines tend to "get the fittings started" on the threads, and then use a wrench to pull everything into position. The results are predictable, with leaks all over the place. It takes a lot of time and effort, but each one of the Tripower fuel lines has to be custom "tweaked" on the bends so that every line can be fully threaded and seated with finger-effort before ever taking a wrench to the flarenuts. It's also important that all the threads be lubricated with a little grease, and that a little coating of grease be applied to the back surface of each flare (the surface that the flarenut rides against). This will assure smooth, proper torque at each connection.

Guys with Q-Jets need to follow the same process when they attach the fuel line to the inlet of the carb: Most aftermarket reproduction fuel lines do not align exactly, and a little hand work is necessary to get the "finger-fit" full seating before tightening. And lube those threads..!

Lars