Building a fuel tank

[Oatmeal]

Hi all,
I'm going to be building a rear tank out of stainless and was wondering if anybody out there with a 23 gal tank could measure and post a diagram with dimensions of their tank.
I don't want to drop my tank until I have the new one built.
Thanks in advance,
Hans

 

[patrickk1]

I had a buddy build one for me. I used dimensions from this forum but made a side-view template of mine to test fit it prior to having him build it. This allowed me to make some modifications to the design to allow more differential clearance since I stretched my wheelbase 5-6" in the rear but maintain fuel capacity.

I'd recommend pulling you tank first so you can test fit with a template.

http://classicbroncos.com/forums/showthread.php?t=220101

 

[JAFO]

Just a suggestion, but if I were to build my own, based on the issues I have had with the Sherman tank, I'd make sure the vent came off the top of the tank some how, or at least make sure the darn tank vents properly. I've had a bit of a problem with venting the tank. Currently I do not fill the tank all the way, so I am sure the vent hose is functioning.
And then just think about how you want to mount the tank and then build it to the size you like. All you need is the measure between the frame rails and front and back opening. You might end up with an odd capacity, but since you are making something custom, make it the shape you like and with the clearances you like. The Sherman tank mounts using a track system, so it was easy to slide it up to how far I wanted it from the floor bed, then tighten the mounting bolts and since it was empty, tack weld its track together so no chance of it coming loose.

 

[DirtDonk]

You going to be using an internal pump for EFI, or just a standard tank with a sending unit?
You going to be off-roading, so ground clearance is an issue? Or just a street driven truck mainly?
Body lift, or no?

So JAFO, have we talked about your venting issue already? Started a thread on it somewhere I can check out?
Maybe I already have and didn't have an answer for you, but would like to revisit it anyway if I have.

Thanks

Paul

 

[Oatmeal]

You going to be using an internal pump for EFI, or just a standard tank with a sending unit?
You going to be off-roading, so ground clearance is an issue? Or just a street driven truck mainly?
Body lift, or no?

So JAFO, have we talked about your venting issue already? Started a thread on it somewhere I can check out?
Maybe I already have and didn't have an answer for you, but would like to revisit it anyway if I have.

Thanks

Paul

I off road mine but, I'm building a healthy skid plate as well.
Thinking about using sender and lock ring assembly off of the old tank if I can modify it.
I'm running an external pump (using a simple TBI setup).
Sherman Tank "rail system" is just plain old unistrut......I'd worry about it sliding down so, I'd add couple of strategic tack welds.
I was hoping not to have to drop to the tank and just rely on someone measurements.
Hans

 

[Oatmeal]

I had a buddy build one for me. I used dimensions from this forum but made a side-view template of mine to test fit it prior to having him build it. This allowed me to make some modifications to the design to allow more differential clearance since I stretched my wheelbase 5-6" in the rear but maintain fuel capacity.

I'd recommend pulling you tank first so you can test fit with a template.

http://classicbroncos.com/forums/showthread.php?t=220101

Thanks for that link!
Hans

 

[DirtDonk]

Yeah, welding the struts is recommended once it's set up the way you like it.

Reason I asked about off-roading was ground clearance. Great that you'll have a skid plate, but I would also recommend a "bump out" forward to put part of the tank under the crossmember to keep capacity but gain some clearance.
The more the better, up to a point. You need to watch for differential clearance of course, but with two or three inches (or more if you have the room) gives you more clearance with the same capacity.

The old NWMP body-lift tanks had a slightly smaller 20 gallon capacity because the bump-out was not as tall. But even 20 is better than 11-13!

You going to keep the evap vents and such? Maybe a return line?

Paul

 

[Oatmeal]

Yeah, welding the struts is recommended once it's set up the way you like it.

Reason I asked about off-roading was ground clearance. Great that you'll have a skid plate, but I would also recommend a "bump out" forward to put part of the tank under the crossmember to keep capacity but gain some clearance.
The more the better, up to a point. You need to watch for differential clearance of course, but with two or three inches (or more if you have the room) gives you more clearance with the same capacity.

The old NWMP body-lift tanks had a slightly smaller 20 gallon capacity because the bump-out was not as tall. But even 20 is better than 11-13!

You going to keep the evap vents and such? Maybe a return line?

Paul

No smog issues as my truck is exempt now (also registered in Utard).
Return line is teed into a vent line but, I think I'll add a dedicated return point.
I've been a sheet metal mechanic for about 33yrs so this shouldn't be too difficult, my tig welding skills are a little rusty though and our shop equipment belongs in a museum!
Hans

 

[sykanr0ng]

Do you really need to use the uni-strut mounting?

Since you are making it yourself there is no need to make it adjustable.

Why not just make angle tabs welded to the tank and bolt it to the frame, like an Aerotank?

Then it could be wider which means it could be shorter in height for the same capacity giving more ground clearance.

 

[Oatmeal]

Do you really need to use the uni-strut mounting?

Since you are making it yourself there is no need to make it adjustable.

Why not just make angle tabs welded to the tank and bolt it to the frame, like an Aerotank?

Then it could be wider which means it could be shorter in height for the same capacity giving more ground clearance.

Not going to use the unistrut but, do want to make it adjustable should I ever want to add a body lift at some future time.
Hans

 

[bronconut73]

Yeah, welding the struts is recommended once it's set up the way you like it.

Reason I asked about off-roading was ground clearance. Great that you'll have a skid plate, but I would also recommend a "bump out" forward to put part of the tank under the crossmember to keep capacity but gain some clearance.
The more the better, up to a point. You need to watch for differential clearance of course, but with two or three inches (or more if you have the room) gives you more clearance with the same capacity.

The old NWMP body-lift tanks had a slightly smaller 20 gallon capacity because the bump-out was not as tall. But even 20 is better than 11-13!

You going to keep the evap vents and such? Maybe a return line?

Paul

That Aero 20 gallon tank is the body lift tank that WH's used to sell?

I remember that and thought that the 3 gallon loss was well worth the ability to tuck it up a little higher.

 

[ntsqd]

No one has discussed the fuel pick-up and that is important to an off-road tank. Suggest researching baffling around the pick-up. OEM EFI tanks have this and OEM carb tanks do not. Which is part of the reason why converted from carb fuel tanks have issues with low fuel level starvation at high angles.

 

[Oatmeal]

No one has discussed the fuel pick-up and that is important to an off-road tank. Suggest researching baffling around the pick-up. OEM EFI tanks have this and OEM carb tanks do not. Which is part of the reason why converted from carb fuel tanks have issues with low fuel level starvation at high angles.

Yeah, I've been giving some thought to that as well. I might build a small accumulator tank and feed it with a low pressure/high volume pump from the main/aux tanks......thoughts?
Hans

 

[DirtDonk]

That Aero 20 gallon tank is the body lift tank that WH's used to sell?
I remember that and thought that the 3 gallon loss was well worth the ability to tuck it up a little higher.

I agree. The slight loss was worth the trouble, but you did not gain any ground clearance with it. It was simply deepening the notch in the leading edge so that the shelf did not contact the crossmember. No gain at the bottom, just the ability to move up with the body.

And no, it was not an Aero tank, but simply a modified NWMP tank.
The one we currently sell from Sunset Fab is supposed to have a compromise version of that, which retains most, if not all of the original volume, but has a slightly deeper notch to accommodate up to a 2" body lift. We do claim a 3" body lift compatibility, but I bet it's really close.

No one has discussed the fuel pick-up and that is important to an off-road tank. Suggest researching baffling around the pick-up. OEM EFI tanks have this and OEM carb tanks do not. Which is part of the reason why converted from carb fuel tanks have issues with low fuel level starvation at high angles.

Just to be clear, in the case of the Sherman and BC tanks, there is some very good baffling around the pump pickup area. The tank itself does not change between carb and EFI. Only the internal pump assembly is needed to make it EFI, or an external pump can be utilized as well if desired. The tank still has the baffling either way.

I don't think that's what you meant regarding carb vs EFI tanks, and Oatmeal is going to make his own so that's a very important thing to consider. But I wanted to point that out for those looking at one of ours anyway.

Paul

 

[ntsqd]

I had only a guess as to what might be inside the various aftermarket tanks, which is why I was careful to say "OEM ___ tank".

The hands-down best fuel pick-up baffling system I've ever seen is in the tanks used in the diesel Rabbit pick-ups. Not exactly an easy one to find for study, and with its rubber diaphragm-like trap door not easy to copy either.

I think that Bronc-up has room for maybe as much as 35 gallons, so I've played around with tank designs & baffling ideas. One idea is to use the weighted "donkey dick" pick-up that moves with the fuel. And then there's Holley's fuel mat pick-ups, which are intriguing and expensive.

 

[JAFO]

You going to be using an internal pump for EFI, or just a standard tank with a sending unit?
You going to be off-roading, so ground clearance is an issue? Or just a street driven truck mainly?
Body lift, or no?

So JAFO, have we talked about your venting issue already? Started a thread on it somewhere I can check out?
Maybe I already have and didn't have an answer for you, but would like to revisit it anyway if I have.

Thanks

Paul

Not sure we really discussed the venting. I do not have the factory plastic can behind the driver's seat. Well, I own the plastic bottle and it doesn't leak, but when I did my restoration I did not cut out the hole for the grommet and tubes. So, thinking this would supply venting, I ran a vent line (gas line) from the vent tube on the tank all the way up front, then ran the line up the firewall on passenger side, then back down (basically ran it up, looped back down) to the old factory canister mounted on the frame. My thinking was my vent line was now above the gas level. But once when I was filling up I filled the tank all the way and I think maybe part way up the fill pipe, and then was close to the office and so hardly burned any gas from station to office. When I came out for lunch gas was siphoning out the charcoal canister. Canister was full of gas and when I got home I had to remove it and drain out the gas. So, now I do not fill the tank all the way up and as I remember I have put a small hole in my gas cap so that it now vents until I come up with something better.

 

[ntsqd]

What I've deduced from studying the system, which means that I could be wrong about some of it: The vapor accumulator/condenser (plastic can) in addition to being a liquid/vapor separator also acts like an upside down p-trap in a way. It is a volume to capture the expanding fuel and that large volume between the line out the top of it to the charcoal canister and the line(s) in at the bottom from the tank is/are the break that prevents siphoning. The fuel would first have to expand enough to completely fill the can before siphoning can happen, and the volume of the can is set such that the full tank of fuel can't expand that much. A bigger fuel tank may require a bigger can for the system to continue to function correctly. Depends on what the original designer set as the maximum likely expanded volume and how that compares to what the new tank is capable of.

 

[pcf_mark]

Can you buy the mounting ring for an internal fuel pump and sender? Not sure how easy that would be to make.

 

[Timmy390]

If I was building my own tank, I would use a HydraMat system for the pickup.

Tim

 

[Joe473]

Good site for parts. Some of the stuff looks very similar to vendor tanks.
http://www.tanksinc.com



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