I'm trying to hook up the fuel line to the tank on my 54 lincoln. I checked the threads on both pieces using proper size nut and bolt and they're both good threads. But I've spent over an hour trying to screw them together but no go. I've put the bolt into the tank and made sure the line fitting was lined up the same angle but it just won't start. The tank is still loose so I can move it around but it's not helping. Is there a trick I don't know about that will help? I know the threads are good and yhe nut and bolt I used do screw together, so I know the fitting and tank should too. Any help or advice would be appreciated, it's just so dang frustrating.
What size and pitch are the "proper size nut and bolt"? Fuel lines typically don't use the same thread diameters and pitches as nuts and bolts.
You're ( obviously) not aligning the fittings correctly , they can be aggravating , keep tweaking the alignment , just a little at a time , you'll get it ..
Have you pulled the fitting back and pushed the flared tube into the tank to make sure it seats down fully before trying to start the fitting? If the tubing seats, then the only other answer is your line really isn't perfectly aligned, and you need to tweak the angle first to get it aligned.
Curl your lips around your teeth, then stick out your tongue just a little. Clamp your tongue between your lips. Wiggle the tip while squinting just a little as you seat the tube in the fitting, then carefully twist the nut into the threads.
A little lube on the threads and tube helps the nut spin with your fingers and the threads to catch a little easier. But as said it's all about the alignment.
Okay, 1/2-20 thread means that it's 5/16 inverse flare. Maybe get a spare flare nut and try screwing that in by itself? Just as a double check.
Some days, that stuff just falls together, other days, it won't work to save your butt. On the bad days, it often helps to just do something different on the project, and do the fitting a different time.
Does the bung in the tank have a tube seat or is it an open hole? If it's an open hole, you're gonna need an adapter fitting to make the connection seal. Possibly a 1/4" npt to 5/16" inverted flare adapter?
The thing about fuel lines in general........ 90-degree bends are from the Debble and are never actually 90-degrees. One end of a line is always going to be easier to thread together than the other end. In your case, the difficult end is at the tank. That bend in the hard line in your photo is probably not pointed 100%, dead nuts square to the tank fitting so the fitting riding on the hard line isn't square either. So many of us are tempted to connect the "easy to get to" end first and then struggle to connect the "hard to get to" end last. Don't do that. Let the other, "easy" end hang in the wind while tweaking all the angles to start the difficult end at the tank. You want the hard line to flop around and follow the fitting, not the other way around. Once you have the tank fitting started but maybe not totally snug yet, then connect the easy end that's out there in the bright light of day. If that's not possible, temporarily detach any hangers, etc., and make the whole run as loose as a goose. You can also try cocking doing everything backwards by wiggling the tank with its fitting at more exaggerated angles with wedges at one various corner or the other. But that's a crapshoot and another hour out of your life. My first suggestion above is the way Jesus and Moses always did it.
here's some thing to read... the fitting is pipe thread... tapered...if some on took a bolt and used a wrench... it changed the thread pitch.. does the nut go on the fitting with just fingers like it goes on the bolt??? I would get a pipe thread tap and case the fitting in the tank... if the nut goes on the fitting on the line someting wong...
heres another read... trying to start a fitting thats cocked to one side messes up the starter thread... here's something to try that allways works for me and is how I always do it to not mess up the starter thread.... turn the fitting to the left till you feel a click with slight pressure... then go to the right... when It clicks is when the starter threads are lined up
This is your answer. The bung on the tank is npt and needs an adapter for the tube nut (not an npt) to seat into.