Making a fuel tank... a couple questions

[Topdown]

Ok... I am going to be making my own gas tank out of 1/4" steel to sit right behind the cab on the flatbed.

63" wide, 12" tall, 8" deep on the bottom and 6" deep on the top... Fuel filler will be on the top, on the driver side. (Roughly a 21-22 gallon tank)

I am not going to run a fuel gauge (at least not at first)

My questions are these:
Do I need to put anything inside the gas tank (I.e. baffles or something)?
Where would the best place be to locate the fuel pickup?
What would be the best way to make sure I dont run myself out of fuel when off-camber? - is that something that an internal baffle will solve?

Thanks
-Ryan

 

[BadDog]

1/4"!!!

Way overkill, and not really in a "good way". 1/8" would be over kill. And yess, you need baffles or something to control sloshing. Some guys just stuff it almost full of plastic oil cans, cleaned out, poked full of holes, and with the bottoms cut out. Look back a few months in the CoG for a post of a tank I designed to minimize fuel starvation (using baffles and a sump).

Pickup goes in a sump if you have one, otherwise, probably on the bottom would be a good idea and near the back (maybe 3/4?) if you do many hill climbs.

Instead of a guage, I prefer a "sight glass" anyway. Can be done with nothing more than a few tube barbs on 90s and some clear fuel line.

 

[Topdown]

In doing a search... (yikes) I have changed my mind on what to use for material. I am thinking Aluminum now...

I still want to stick with the same dimensions and I have more questions.

Are more baffles better? With such a long narrow tank would it be smarter to run the bottom rear width of the tank angled to an even lower sump or is simply putting in a sump enough as long as the baffles direct any/all fuel across it?

 

[dyeager535]

If you run a fuel return line, and an effective sump/baffle setup, that will net you more "capacity" in angled/low fuel situations. As long as the return dumps into the sump, it will "recycle" the sump contents instead of having to draw from the rest of the tank.

I know that at least some fuel cells run foam inside of them, I'd think that would be about the best material to prevent fuel slosh, IF it doesn't take up too much capacity. In stock carbed applications, there is usually a vertical piece of steel "behind" (towards the back of the rig as installed) the sending unit.

 

[ntsqd]

I posted a baffle design pic to this thread.
So far a sump of any sort has not been needed with this design. The more the baffles overlap the more fuel volume they will hold near the pick-up when at an angle.

In my current design for Patch's new tank I'm planning on flanging the baffles so that I can easily weld them to the bottom and the top. Since the top is the last part to go on the tank I plan to drill hole thru the top centered on the flanges and Rosette weld the flanges to the top from the outside.

Regardless of the metal you make it from, consider using some of this to seal it from rust or corrosion.

 

[dyeager535]

Is there a reason not to go with the design GM used for the TBI applications?

IMO it looks to be about the easiest way to "lock" fuel into the pickup area, although I guess to duplicate the plastic piece in metal would take a lot of welding effort to make sure all the seams were leak-resistant.

 

[merace19]

Fuel foam like the race cars use does not take up hardly any room as far as fuel capacity. But it does break down over about a year maybe 2. You have to pull it out and restuff it with new. If you dont your fuel filter will get a work out. I have raced for over 15 years and i know the hard way on this. Have you considered a race cell from one of the many race shops online? Fuel cell is one place i would not be cheap on and you looking like a piece of cooked chicken is not a GOOD thing.
Also my 70 Chevy truck had a tank inside the cab(behind seat) that if they made replacements for it you could box in and use on the outside of truck. That way you can box with aluminum and not have to worry about your welds being perfect.

 

[Topdown]

What design did GM use? I have never seen anything on it.

Is there a reason not to go with the design GM used for the TBI applications?

IMO it looks to be about the easiest way to "lock" fuel into the pickup area, although I guess to duplicate the plastic piece in metal would take a lot of welding effort to make sure all the seams were leak-resistant.

 

[Topdown]

I have gone down the "fuel cell" path and they dont make one even remotely close to the dimensions I am looking for... which have changed since my original post... I am now looking at a 48" wide, 10" tall tank that is 8" at the top and 12" at the bottom (angled)

In the last day or two I have been debating on whether I want that fuel that high, effectively raising my center of gravity. dropping it between the frame rails seems like a good idea, like a stock blazer, but that would mean a whole different setup.

I am interested to see (if anyone has it) what the inside of a stock GM tank looks like. What kind of baffles? what kind of pick-up? etc...

-Ryan

Fuel foam like the race cars use does not take up hardly any room as far as fuel capacity. But it does break down over about a year maybe 2. You have to pull it out and restuff it with new. If you dont your fuel filter will get a work out. I have raced for over 15 years and i know the hard way on this. Have you considered a race cell from one of the many race shops online? Fuel cell is one place i would not be cheap on and you looking like a piece of cooked chicken is not a GOOD thing.
Also my 70 Chevy truck had a tank inside the cab(behind seat) that if they made replacements for it you could box in and use on the outside of truck. That way you can box with aluminum and not have to worry about your welds being perfect.

 

[ntsqd]

All of that effort for a 20 gallon tank?

Seem like there ought to be something out there already existing, or close enough. Have you looked thru the tanks offered by boat places like Overton's?

 

[CyberSniper]

"baffling" on the tanks I've watched my neighbor build is pretty simple.

Just take some 16 gauge steel and orientate pieces so they go perpendicular to the driveshaft spaced 2" apart. They only need to be 7/8 the height of the tank. Put two 1/4" notches at the bottom on either side with the notches being staggered at least 4" between pieces. Tack weld them in place. Then take one piece and notch it so it'll fit over the other pieces and tack weld it in.

 

[Topdown]

yep... so far, nothing... though its beginning to be more of an option. I dont want a fuel cell full of foam and thats what most places sell.

All of that effort for a 20 gallon tank?

Seem like there ought to be something out there already existing, or close enough. Have you looked thru the tanks offered by boat places like Overton's?

 

[dyeager535]

GM simply made a plastic rectangle...plastic on the bottom, and 4 walls. On the outside of the base "rectangle" there is a gap between the sides of the rectangle and then another "wall".

It basically looks like a maze where you circle the center and spiral your way in. The fuel enters the pathway on I *think* the drivers side, (as installed in vehicle) travels forward along the drivers side of the "sump", turns along the front of the sump, takes a right and heads towards the back of the truck. The base rectangle has about a 1" slot cut in it, so the fuel that travels from the tank makes it in to the center.

There really is nothing more than this plastic "maze", but it is effective because the fuel has to travel around so many corners. Once the fuel gets in on flat ground, off-camber isn't an issue because the fuel is trapped. The walls on it are probably 6" tall or so, when the tank is full, fuel just covers it.

Only problem with the design is that GM riveted the plastic to the botom of the tank, and the plastic eventually breaks.

Pick up and everything else is standard among most older GM fuel tanks, it just hangs down into the center of the sump. Obviously carbed tanks won't have the sump. Sorry I don't have a picture of the sump, but I think my description is somewhat clear.

 

[Yukon Jack]

Have you looked into what you will do for a vent line yet?

My tank has a threaded fitting next to the sending unit and right now it has a fitting and an elbow that points it down. You can see it here on the right side of my tank.

I'm not sure how I ought to terminate it - maybe a length of hose with a breather on it? Seems if it is open I would have gas evaporating all the time.

Let me know what your thoughts are on how you will vent your tank.