Fuel leak at carb attachment

[dunagan]

I have a 1967 427/400 w/ a fuel leak apparently at the connection of the fuel line to the carb. Which nut is the culprit? THe large nut appears to have a washer and the small nut secures the flared end of the line. Is there a "special" trick to keep this connection dry? Any tricks to the tightening routine?
I have heard this was a common problem. Is there anything that can be applied to the nut to seal it?

I have checked the nuts and both are EXTREMELY tight so there does not appear to be a loose connection.

Thanks for any suggestions.

 

[cntrhub]

Which nut is the culprit?

You might want to look into new line fittings. If you cannot find any OEM or aftermarket from an auto store, try one of the racing fuel line companies. Usually the pipe's taper is either squished from over tightening, or the tip has a stress crack near the taper.
Which one is leaking? Take a cardboard or hard piece of cray paper, and cut the paper so it will fit snugly, (so as not to blow away when the fan blows over the engine) under the two fuel lines. Draw a pencil line across the paper. Place it centered between the two fittings. Start the car just enough to pressurize the fittings. If the engine ran long enough, and the leak (minimum droplet) occured, you will see a fuel spot on the paper. Which side of the penciled line the drop occured, will pinpoint the faliled fuel line.

 

[RalleyRed]

If it's leaking from the threads try Teflon tape, seems to work well for me.

Cheap and easy too.

Rick

 

[chevyaddict]

I agree - Teflon tape always does the trick.

 

[JohnZ]

Although Teflon tape may temporarily stop a minor leak, it doesn't address the root cause; the seal is between the flare on the steel line and the tapered seat in the fitting, not in the fitting threads. Teflon tape or Teflon TFE pipe dope on the threads can help get a good mechanical seal at the flare by reducing thread galling or friction with lower fitting torque, but if you have a fuel leak (NOT a good thing - hope you carry a fire extinguisher), you're much better off to address the root cause by replacing either the steel line or the fitting, or both, to stop the leak permanently. A little TFE pipe dope or anti-seize on the fitting threads will reduce the possibility of galling the threads, and will make it much easier to disassemble later without damaging the threads.