Technical AN vs 45°flare fitting?

I need to hook a gas line up to a recent fuel tank install on my 60 suburban. The tank is a 38 Chevy tank, so there's been some mod work. End of day, I'm having to use the fuel pickup that's built into the tank and exists through a 3/8" NPT fitting.

My question regarding this is, is one fitting better than the other and why?

The 3/8" NPT bung is on the rear driver side corner of the tank, so I need to run a fuel line up and over to reach the existing line coming out of the fuel filter in the general sta of passenger side rear differential. I called summit to order the fittings to do this fairly easily. At first we were going to go 3/8npt to -6an fitting then flare a line for that....I don't have the flare tool for this and if not mistaken it's a tricky flare. If not there was a reason we discussed another few options. Hmmm! I know an inverted flare, which I don't have good luck with.... at least not with steel line. He finally settled on saying get some 3/8" aluminum fuel line (I have a bit of 3/8" steal), a 3/8npt to pipe fitting adapter, then a reducer nut and a tube nut for inverted flare. He said the aluminum will easily do the inverted flare and should work great.

While I wait on the parts I'm curious about the reasons to use once vs the other. I'm about ready to start another project which will be all new lines again. I actually thought he said with these parts I just needed to put a 45 flare on the line, which I can get on my steel line, it's inverting it I have trouble with. Rereading the parts list to post this made me realize I'll have to do an inverted 45 flare for that tube nut. I obviously don't want fuel leaks.

 

A-N fittings, (Army Navy) fittings use a 37 degree flare. They are listed in what's called Dash Sizes, times 1/16", meaning a dash 8 is, 8 x 1/16" = 1/2". A dash 12 is 3/4", fairly simple. Each flare uses a tube nut and a tube sleeve behind the flare. You can not use these fittings with a 45 degree flare. A-N fittings are used on stainless steel tubing, braided line and many components are plumbed for A-N flares. Fittings come in aluminum, stainless and plated steel. I find that they look nicer and are actually easier to use. If your parts guy is telling you to use a 45 degree flare with an A-N tube nut he is wrong.

 

He didn't say to use an AN tube nut. It's a tube nut for inverted flare

 

I think you're getting confused with the inverting part. It's only the type of nut used to secure the line.
Is the fitting on the tank male or female NPT? One simple adapter on that to allow use of the inverted flare system. Sketch or picture of the tank fitting, and we can tell you what parts will work.

 

Here's a screen shot of the parts and the tank.

 

Doesn't look like good place for the fuel outlet to me.

 

Not thrilled with it either, but it's the only option I have at the moment. I can't find a 5 hole sending unit with pickup for a 7-1/2" deep tank. I tried to modify my stock one but it won't fit with the float arm modified.

 

Ditto on woodiewagon46 said. Fuel thr float was inline with the pickup and it had a 45% you might fit it into tank

 

Something like this would be pretty simple to do. 3/8 pipe to -6 jic

 

Did my whole fuel system in -6 AN with mostly hard line. The trick to getting good flares (AN 37*, SAE 45* or inverted flare) is the Eastwood flaring tool. It is absolutely worth the money. Did all my lines in stainless. That fitting shown above in Post #9 should actually have a 37* single flare on it for AN fittings, they are not compression fittings like copper lines use.
SPark

 

LM14, beautiful chassis work, it's almost a shame to cover it with a body.

 

With the outlet up a bit in the tank, looks like you need to make some sort of pickup tube. Get a 3/8 NPT to 3/8 compression fitting. The line will slide through the fitting, and you can bend it down, s othat it reaches close to bottom of tank. Mark the line so you know which way the bend is going. Don't tighten it up yet. Install, the fitting, slide the line into the tank through the fitting. Slide the compression ferrule on, then the nut. Ensure your pickup tube point down, tighten the nut so that the line is compressed. No flare, and it's good to go. The compression fittings work with pressure, so will be fine with gas with none.

 

There is already a pickup tube inside the tank. It's factory built in where the 3/8 not fitting will go.

 

I'm a bit confused on the fittings I showed do I do a double inverted flare or just a single 45Degree flare? Is there anything wrong with what's shown in my parts list?

I am not sold it'll be permanent but I need to get her back on the road. I may still play with modifying the stock style pickup until I can figure how to get it to fit..... I've wondered what would happen to 3/8 rubber fuel line sitting inside a tank. If I could splice the pickup tube on the assembly, I might be able to get it in. Or maybe I can do something similar with the float arm.

 

That's good, couldn't tell from the image. You can still do the same as I suggested above then, only you don't have to feed line through to make a pickup. Just push line in, with ferrule and nut and tighten it up. I've done this with steel line, SS and copper tubing. Use whatever line you prefer.

 

With the compression bubble, you don't need to do a flare. If you prefer to use a flare, then you need a NPT to inverted flare fitting. I don't know why you need a reducer bushing(from your list) unless that hole in the tank is not 3/8 npt. You had a 45 degree adapter listed, they are also available in 90*, if you want the line to turn right down, at the fitting. Otherwise, you can just use a straight, and bend the line to where you want it to go

 

I opted for the 45 degree fitting so that I could easily clear the lip a few inches up. Figured I can get the line going away from cross member and then bend the line approx 45 degree vs several bends.

The 45 degree fitting is NPT on both sides, so the 'reducer' is taking from npt to inverted flare. Not sure if they had a 45 in npt to inverted, I just know vs spending hours digging through their fittings online, I called and that was an option he came up with. Obviously lots of ways to skin this cat.

I like the compression fitting idea as well. Probably could have picked up local at an ace hardware. I also really love the AN fittings and trust that the Eastwood flaring tool it's worth the money, maybe some day. I considered it when doing all the brake lines on this, but then found a brake shop that would flare the lines for me for a few dollars a flare, so went that way.