Trying to get some ideas on adding dual gas tanks to 56 Ford F-250 long box flatbed with stock 272 Y block. On this project, Im going for the "big truck" look with long bed, smoke stacks, and duallies. I want to remove the gas tank out of the cab. In keeping with the big truck look, I would like to have a fuel tank fabricator build me two side tanks approximately 16" in diameter and 24" long.

It might be a real pain having to fill the tanks seperate (one on each side of the truck). I think my first choice would be to tolerate that opposed to all the plumbing and headache of making one single fill for both tanks.

This is not a truck that will be used every day and seldom on gravel roads or winter driving.

If I split the tank to fuel pump supply line with a "Y" fitting, will it draw equally from both tanks (providing I always fill both tanks at the same time).

If the answer to this question is yes, I am assuming I could connect the stock fuel gauge to just one tank for a reliable fuel gauge reading. In other words, when the fuel gauge reads 1/2 full, I would have 1/2 tank on both sides.

If the answer is no, I have to figure out how to add separate supply lines, gauge wires and fuel floats to each tank. That's going to take a little more research.

As far as what I would need to have built on each tank, I would include an external fuel gauge on each tank. I would include a fill spout on each tank. I would include a fitting to accept the stock fuel tank pick up tube on the top of each tank to get fuel from the bottom of the tank same as the stock tanks. And I would include the stock fuel float connection on top to operate the stock fuel gauge (either one tank or both tanks if needed).

Anyone have any suggestions?

 

I'd take a look at how the mid 80s GM trucks with the saddle bag tanks are wired. With ours, there is just a switch in the cab to swap between the tanks. As long as you keep the lines primed in both sides, you can even swap while driving down the highway. Then you don't have to fill both tanks at once each time.

 

Thanks Fladoodle. If I remember correctly, those saddle tanks had a fill spout on both sides for each tank. I can live with that. I have done a little research on that method but am hoping to use it only if there is not an easier way. I never thought of having to "prime" one supply line if it ran dry. Also, not sure how a stock 56 Fuel gauge would work with a dual tank set up.

In my research, I came across an article that suggested if you are pumping fuel from a stock fuel engine with a mechanical fuel pump, the pump will draw equally from both tanks with a "Y" connection. It will always draw from the tank with the most gas in it. The logic behind this theory was that because one tank would always have a little more fuel than the other, the easiest path for the fuel is the one with the most pressure to the system.

The tank with the most gas takes the least pressure to draw the gas.

Sounded pretty far out to me and I kind of raised my eyebrow. Could it really be that easy?

 

Just thinking out loud here............the fuel tanks on these old trucks is supplied to the fuel line thru a pick up tube that enters the top of the tank. The pick up tube enters the top of the tank and goes to the bottom of the tank. It stops just short of reaching the bottom of the tank. Two possible reasons for this design. One, there is no fuel line connection at the bottom of the tank to deal with when removing the tank. I would not give that reason a lot of credibility since all the tanks I have seen also have a drain bolt to remove all the fuel from the tank.

Reason two could be to avoid letting the sediment in the bottom of the tank enter the fuel supply line. I'm thinking that is more likely the reason for the pick up tube taking fuel out the top of the tank.

When you think about the idea of two gravity fed tanks equalizing, one constantly trying to match the other, it makes sense it would work. But in the case of a pick up tube on top of the tank, if the tanks equalize, it would be only because of the volume and weight of the fuller tank constantly changing and creating an easier path for the fuel to be pumped by the mechanical pump.

Going to take someone a lot smarter than me to tell me if this will work.

 

Sounds like an interesting truck, stacks and dually does that mean it's diesel?

You say "Big truck look" so you're talking two round aluminum or stainless visible saddle tanks? If so then a filler on either side with a cap right on each tank is keeping true to the look as that's what trucks have.

I can think of two viable ways to plumb and wire the tanks.

Back to the big rig stuff, many of them use a "balance valve", really it's just a "T" with a valve setup to shut off one side or the other manually from underneath. This has problems though, heavy trucks are rarely on uneven ground, the tanks are tall, not filled all the way, and don't have vented caps. All of this makes them able to tolerate a direct connection between the tanks. You however are likely to have at least a couple of those issues. Meaning if parked at an angle it will drain from one tank to the other possible overflowing the downhill tank.

A MUCH better way is to stick with FORD parts, not GM, yuck. 80-87 dual tank trucks WITHOUT EFI and 84-94 Pre-powerstroke diesel use an electric valve that can also internally switch both fuel pumps and gauge.



This valve is switched with just a single simple toggle switch on the dash. When selecting tanks it not only swaps the plumbing but acts as a relay switch to switch in tank pumps and the gauge. So your single gauge is reading whatever tank is selected. You do not need in tank pumps, the diesels don't have them, it will draw through with a mechanical pump on the engine, ya just don't use those wires.


This is what I strongly suggest and would do myself, I own 4 trucks with these valves and have yet for one to let me down.

 

After your last post while I was typing I have another suggestion. If a simple "T" is desired then 90s EFI trucks have fuel check valves. They just switch the pumps and keep it from back flowing with check valves. If you did a "T" with two check valves it would draw from whatever tank have the higher fuel level automatically but would not cross flow and overfill the downhill tank unless the check valve failed.


Left Tank ---> Check Valve ---> "T" <--- Check Valve <--- Right Tank

 

Thanks Brute. Its actually a 272 Y Block that was used for hauling grain in Great Falls, MT. I cam across it for a good price and fell in love with it after seeing some of the bigger F Series Ford trucks posted from members in this forum. I have two 56 Ford F-100 in progress, but wanted to take this one on for something different.

I am picking up a lot of experience with this truck and this build will help me when I get back to the F-100 short boxes. I just really liked the idea of doing this one different than the standard F-100 Build (still my most favored truck ever).

Your suggestion definitely looks like a good option. Just to clarify, I do plan on having a fill neck on each tank with vented gas caps. Looks like I need get a fuel sensor in both tanks and an electric valve for dual tank Ford 80-87 without EFI, or a Ford 84-95 Pre Powerstroke diesel with dual tanks.

Your thinking I can use this with the mechanical fuel pump on my 272 B block and the electric switch that controls it will swap tanks and also work the fuel stock fuel gauge. Is that correct?

 

This was more in line with my original idea. I was thinking tanks trying to equalize would be an issue with gravity feed tanks supplying the fuel line but not with pick up tubes which enter the top of the tank. Am I missing something there?

 

Yes, the stock mechanical pump will draw through it, you just won't use the wires to switch the electric pumps or the fittings for the return lines. But nice that they'll be there for an upgrade later.


Also, for the tanks themselves, there are a wide variety of air tanks out there to be found. Likely you can find a couple in the dimensions you want then add fittings. It'd be cost effective, make for a tough tank should it contact the ground, and make fabrication of fittings/filler and brackets easy and sturdy.

 

It would work, you'd just have less control and would still need a way to switch the gauge, though a toggle switch would do that. If you added a couple manual valves it would give the ability to shut off a tank or both, but would have to be manual from underneath.

Left Tank --> Manual Valve --> Check Valve --> "T" <-- Check Valve <-- Manual Valve <-- Right Tank

 

Im going to call one of the vendors this week who make the stock tanks and ask some questions. Meanwhile, if anyone has any more thoughts on this, please jump in. I appreciate all the input I can get.

 

Put a mechanical valve with the handle running into the cab between the seat and the door. This gives you the ability to select each tank separately. My 73 had this set up, my 56 has the set up. Both run mechanical pumps and there is no problem running a tank dry and switching. Just a few seconds till fuel is picked up from the second tank.
So far as a gauge, install a Stewart Warner or similar sender in each tank with a switch to a SW or other aftermarket gauge. Chances of the original Ford gauge working are slim to none.
Edit: If plumbed correctly, no check valves needed.

 

Theres that good ol Missy Green again, man I love that truck. Thanks Ray.

 

Back in the day I worked with a large C...y vacuum truck that had the setup Ray described. Had a switch for the guage/sender though. Worked pretty well, but you had to remember to flip the switch after turning the valve.

 

Hey Toby, was it a stock set up or add on?