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5/16" fuel line addapter 1/2"x20


OUTFXD
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So... Ordered a new fuel tank. Straps and insulators. Put it in the car and everything was 100%.  until I tried threading the hard line in to the fuel pick-up.

 

Instead of an inverse Flare nut,  They welded a SAE 1/2"*20 bung to the tank. It took some work, but I managed to get the stock threaded piece threaded. Of course without a proper fitting the hard line has nothing to push it back against the threaded bit meaning it wouldnt sinch down.  

 

So,  I went to the local Lowes and looked for a Hose barb that was 1/2"-20 threaded as the bolt on the tank and 5/16 OD so I could just use a length of fuel line to patch it together.

 

Turns out they only do fittings in NPT.  I tried the closest to the bit I had, but it wouldnt thread into the tank.

 

I tried the internet but they seemed desperate to sell me a NPT thread fitting.

 

Any suggestions on  easily available Fuel line adapters? 

 

Thanks!

Fuel Line addapter.jpg

Edited by OUTFXD
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A 1/2-20 straight thread it would seem to me would be sealed with an O-ring shoulder to shoulder (with the O-ring groove in the fitting).

My first visit would be a Hydraulic Shop. The guys that make up hoses and have all the "AN" fittings.

At first it may seem the tank makers did you wrong but you might find they've done you a service.

To communicate what you need take a photo of the tank and the line you wish to connect....they may have an idea what the tank maker had in mind.

 

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7 hours ago, Sam Buchanan said:

Your tank has a 1/4" NPT thread. I hope you didn't ruin the threads when you forced the original fitting into the tank......

 

I was curious if the thread would end up NPT thread, but I couldnt find anything to support that.  and the original  fitting never got beyond lightly difficult to thread. Just being attached to a hardline, it didnt want to line up.

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Use a 1/4" NPT fitting with a barb in the tank, then a short length of 5/16" rubber hose, then a filter, then another length of hose to connect to your new fuel line. The NPT fitting does not need the little ferrule that was in the original tank.

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1 hour ago, Sam Buchanan said:

Use a 1/4" NPT fitting with a barb in the tank, then a short length of 5/16" rubber hose, then a filter, then another length of hose to connect to your new fuel line. The NPT fitting does not need the little ferrule that was in the original tank.

That is my current plan.  I am also going to run a tap down the hole just to make sure the threads are clean.

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Make sure it is a NPT tap! If you use the wrong tap it will destroy the taper of the threads. I would try installing the fitting before you resort to a tap. It could be that once you get the fitting started it will thread in and tighten nicely. Some sealant on the threads is a good idea.

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   When I replaced the gas tank in my first addition 49 Coupe, I was aware that there is a special long ferrule, that allows for the ferrule to tighten the gas line connection. After removing the fuel line, I took a pick and got it out of the outlet and put the ferrule in a safe place. The new tank required the long ferrule to complete the fuel line connection. Others have bought tanks that did not require it, mine did. It could be on the tank outlet or on the ground where you removed the old tank and moved it. Mopar-Pro wants $30 for that part. 

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I have been following along here because I suspect I will have the same problem soon also.

 

The original line is a simple hard line flared on the end.

I looked at my new tank & saw that a flared line will not work with the tank without a adapter of some sort. .... rolled my eyes and thought that is a problem for another day.

 

I would like to thank @Sam Buchanan for the hint it is 1/4"-18 NPT.  ..... I have that tap I can double check. When I pull it back out of the attic for installation.

 

In this area I also would use a good sealant.  (pipe dope) A long time ago in another lifetime, I worked around boilers and lots of plumbing.  Pipe dope was the sealer of choice.

Later on as a remodel carpenter I would use Teflon tape for chrome plumbing fixtures & visible connections under a sink. .... Was clean & pretty.

I had to go back more then a few times to redo the Teflon tape because I did not use enough the first time.   You use too much & the excess looks stupid & needs to be cleaned off.

 

Pipe dope is messy, will take time to clean off the excess if you care, I never had to go back and redo a joint when I used pipe dope.

 

 

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14 hours ago, 9 foot box said:

   When I replaced the gas tank in my first addition 49 Coupe, I was aware that there is a special long ferrule, that allows for the ferrule to tighten the gas line connection. After removing the fuel line, I took a pick and got it out of the outlet and put the ferrule in a safe place. The new tank required the long ferrule to complete the fuel line connection. Others have bought tanks that did not require it, mine did. It could be on the tank outlet or on the ground where you removed the old tank and moved it. Mopar-Pro wants $30 for that part. 

 

I recently replaced my 50 Plymouth tank with a new unit from Mopar Pro. My original line had an extra long fitting and no ferrule. Mopar Pro told me I needed the ferrule. Turns out you either need a regular inverted flare fitting plus the ferrule, or the longer fitting. It seems like some cars came with no ferrule and the longer fitting. I couldn't get the longer fitting to bite with the ferrule installed. I ran a new line with an inverted flare fitting and the ferrule and it worked great with no leaks and no pipe dope or sealant required. 

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This from the 'Whatever It's Worth' department...

 

I think some of the confusion about aftermarket fuel tank fittings is due to the similarity between a flare brake line fitting and a 1/4" NPT fitting. Here they are side-by-side:

 

image.jpeg.d6a8916dac6c9af0bd0712b8fb075282.jpeg

 

 

The NPT fitting on the right is about 0.020" larger and the thread pitch is *slightly* different from the flare fitting. The NPT fitting won't fit in a female flare bung but the male flare fitting will thread some distance into a 1/4" NPT female fitting before the threads develop an interference fit. The NPT fitting tapered so it tightens properly but the flare fitting is not tapered.

 

I suspect....but can't say definitely.....that there are aftermarket tanks out there where someone has screwed a flare fitting in a female NPT bung on the tank. Yes, it will get tight if you are lucky but it is due to the threads of the fitting not matching the threads of the bung.

 

My advise for anyone who purchases a MoparPro tank to try a 1/4" NPT fitting first. If it screws in and tightens after a few turns, then back it out, dope it, and put it back in until it is tight. The NPT fitting does not need the little ferrule that was in the original tank.

 

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