Bulkhead AN fitting on stock fuel tank

[My427stang]

Has anyone added a bulkhead fitting to a stock tank for a return?

I am considering a pass through fitting, which will allow me to run a return for EFI, however, it is an in-cab tank on my F100 so looking for something that I know will seal well on stock flat surface, standard sheet metal tank. 

Many of you guys want me to ditch the in cab tank, I hear ya... but no plan to at all, not even an option as I am trying to keep it as factory stock as possible.

[HarleyJack17]

Following for the same reason, in the future!

[427LX]

I have used on in the bottom of my tank (1985 Mustang) for years as the gravity feed to my fuel pump/carb.
After popping hole using chassis punch/die I put a flat washer outside on fitting and inside the tank under the fitting nut.
I coat the sealing sides of the washers with the Permatex brown Aviation sealer the thick  stuff with brush applicator.
Never have an issue with leaking even when using E10 pump gas.

[Bolted to Floor]

I used the this from Jegs for the Mustang.

https://www.jegs.com/i/JEGS/555/110560/10002/-1

I didn't use any extra sealers, just let the washers do their job. I haven't seen any leaks or drips under the car or smell gas when I'm laying down there by it. I just had to be careful to make sure I could get the parts threaded back together working through the hole for the sending unit.

[cjshaker]

This is what I used for AN line on both sides of the bulkhead...

https://www.summitracing.com/parts/sum-220837b

[RustyCrankshaft]

I've done this quite a few times for different applications. I always use a good backup washer and put a thin coat of ThreeBond 1211 sealant on it (what I've used for years to seal the crank case halves on my dirtbike and quad 2 strokes). It's a semi-hardening sealer designed to be used with gas and methanol. If you can't find ThreeBond locally your local Yamaha store probably has Yamabond 2 which is similar product and still works better than automotive RTV's for something that is heavily splashed or submerged in gas.

[Pentroof]

For my Sniper installation, I also wanted to keep the in-cab tank. I plumbed the return into the collar on the filler neck. I like this because it leaves the tank unmolested.
Truck is a ‘70 F100.

[Pentroof]

I may replace the external fitting with a smooth bend 90 degree AN fitting to reduce any restriction, but this is working fine and my pump is happy.
You can see the sealing washer in this photo, but with a properly sized hole, not sure it’s even needed, as this isn’t submerged and the collar is rubber. No leak, ever.

[Pentroof]

I originally had the 90 flipped around, as shown below, but that would cause enough splash back to trigger the gas pump safety. Flipped it to put the short side on the interior and all is good.
Also added a Teflon tube to return at the bottom of the tank. Teflon is the only truly fuel proof polymer these days. Even so called submersible lines have limitations.
I have enough of the Teflon tubing leftover to make another one...it’s yours for the asking.
.
.

[Pentroof]

Do yourself a HUGE favor right now if the rubber cover is still on your sending unit float. REMOVE IT!

This is a cover that was added to eliminate any sound of the float tapping on the tank. Well, mine deteriorated and came off and I chased a fuel issue for a week because of it, replacing both filters and the pump. Finally found a piece of the cover was stuck in the end of the pickup.

Luckily, I don’t have any ticking sound from the brass float.

[My427stang]

Thanks everyone

Jim - my rubber cover has been gone since the 80s...owned this truck a long time.  I can hear it if I hit a big bounce but rarely.  I considered doing what you did, but I think I am going to have a local tank repair place poke two holes.  That way I can run dual 3/8 or maybe even 1/2 line like I do on my Mustang.  Although the stock 5/16 is likely fine on the pressure side, might be easier on the pump to give it the 1/2 feed it's designed for.

I think I will look to build a standoff with a piece of tubing and a screen for the pickup, and something similar but angled for the return to keep it away from the pickup.  I need to look closer today, but my thought is on either side of the sender, so I can get in there to feed it up through and put the nut on.

Appreciate all the feedback, looks like the bulkheads are pretty common

[Yellow Truck]

Not saying this was clever or the best option, but I replaced the stock line with 6AN plumbing with no return (had thought about using the original line as a pressure return but was assured having two different diameters would result in higher than desired pressure at the carb inlet so went with a single line).

I had the tank out of the truck for this, but my buddy did the same thing to his 67 with fuel in the tank and the tank in the truck. He is braver than I am.

https://flic.kr/p/2g6Mpfr

I used a 6AN bulkhead, and a Russel 639203 6AN to 3/8 adapter, and a piece of brake line tube to make the pickup. If you are using it for a return you won't need the other two parts.

For some reason I can't get the image to post directly today (haven't done it in a while). I had to remove the float and sending unit and bend a wrench to hold the inside of the bulkhead fitting, but it wasn't too difficult. The gasket had perished so I used a little RTV to seal it, but it seems I used a lot more than I thought because a rather large amount got sucked into the pickup and all the way to the first filter (in front of the Holley Blue I was running at the time. Luckily it died in the driveway so no humiliating hook to get home.

[Yellow Truck]

BTW Ross, I kind of like driving around on a tank of gas. Makes me feel like a real daredevil.

Actually, compared to the tank locations on GM trucks of the same era in cab was pretty safe. If something hit you hard enough to rupture the fuel tank you where already probably dead.

[Pentroof]

If you’re cutting the tank anyway, and doing away with the stock fitting, you should have enough room to add a second hole the same size as the sending unit. This would allow fabrication of a plate with both straight through bulkhead fittings and lines mounted to it that uses a factory gasket.
If you’re having it cleaned enough to cut holes, and it’s clean enough to weld, a ring can be welded to the top surface sufficiently thick enough to tap threads.

[cammerfe]

I have put return lines on two different fuel cells using bulkhead fittings. Straightforward installations. The first one was when I removed the in-cab tank on my '63 Effie ICB. I replaced it with a 25 gallon cell in the bed. The second was a 5 gallon in the trunk of my Lincoln to feed the spray system with methanol. No problems.

KS