Building an Under Bed Fuel Tank from Scratch

[duwem]

Anyone built one? Doesnt appear to be much to it. Build a box, add the flange for the fuel pump (doing a fuel injected GM engine), add a filler neck and some mounts to attach it to the frame. I assume some baffles inside would be good, probably just some vertical plates running almost all the way to the bottom?

I have a tig welder and would want to make it out of stainless.

Can I get the fuel pump flanges from somewheres? Weld on filler neck parts for a bed floor filler?

I have seen them priced for $900-1000 with a pump. Have to think the pump is $200-300? Maybe $100 in materials? another $100 for a real nice filler? Thats 1/2 of what a purchased one runs.

[mr48chev]

I think it all depends on your personal welding and fabricating skills. Are you up to the task. If the flange for the pump is just a flat ring could you make it yourself and weld it to the tank?

You would need access to a brake to bend the metal and you would probably want to put baffles in it. The guy who made the tank that is in the back of my 71 did an excellent job of making the tank but it is a 35 gallon one that sits at the front of the bed. It's coming out though as I want to put a tank under the bed if I keep the truck.

[OrrieG]

Tanks Inc. has all the bits and pieces to make your own. I thought about it but ended up getting one for not much more than the materials and I wasn't confident in my ability to get an absolute tight tank without alot of rewelding and grinding. Do a search on line, there are a couple of threads that show up that show the extent of the baffles inside to keep the fuel where it should be and the pickup covered when the fuel gets low. They are not just big empty boxes, I had to modify my float quite a bit to work around the baffles.

EDIT here are a couple of photos of the baffles, pm me with an email, I have 10 photos I found online of the build.

[tmoble]

look at the fuel pump modules on an Impala SS, build the tank deep enough to hold it. Pump, strainer, gauge sender, baffles, electrical, all in one.

[jfnar]

Just a suggestion if you do decide to make you own. I used to work for a company that made auxiliary tanks for pickups and they tested for leaks by putting 2-3 psi of air pressure in them and brushing soapy water on all the seams. Any leaks will give you bubbles. 2-3 psi doesn't sound like much but a rectangular tank won't take much without bulging. A professional welder can get leakproof seams but it's pretty hard for a hobbiest like me. You do need baffles. Good luck on it.

[duwem]

Looks like a lot of science in those baffles.

I'm pretty good at welding, and with a nice tig you can really get things tuned in.

On the Impalla SS pump, what year and what kind of HP can it support?

[tmoble]

check this thread on Chevelles.com:

http://www.chevelles.com/forums/show...mpala+Gas+tank

some stuff in there and links to more. starts about post #5. see Mike's post #9. links to his stuff on LS-s tech

[Tri5Nerd]

How bout doing something like this? See post #29
http://67-72chevytrucks.com/vboard/s...light=tri5nerd

Tri5

[jimig1]

I plan on doing this http://www.classictrucks.com/tech/11...ank/index.html I guess it will depend on where you want the filler at. I was going to buy the tank local so I don't have to pay for shipping.

[Kid]

If your fab / welding skills are up to snuff, dig in, its not to difficult, but is time consuming, I've done a few from aluminum, best time I could get was 18 labor hrs. jfnar is right about bulging, when I pressure check at 5 PSIG, I use a steel tube cage I fabed to keep the vessel from bulging.

[hotrodrookie]

I built mine out of .125" aluminum. Its nice to work with, light, and cheaper then stainless (sheet metal and bungs and fittings that have to be welded in). But if you dont have AC capabilities with your tig machine then its out of the question. Baffles are a must on fuel injected tanks, but there isnt too much to them. Just make sure if you use an internal fuel pump that you surround the pickup with a slosh tray so that it's always submerged in fuel. I made my baffles similar to an egg carton for ease of fabrication as well as rigidity. Geometry can be your best friend when it comes to preventing warpage.

Im my truck I'll be running a 5.3 vortec so I got a used fuel pump from an ls1 camaro to put in my tank. My original plan was to utilize the housing the pump came in and just fasten it in the tank but I had already made my tank before I got the pump and the pump was an inch too tall to fit in my tank. I ended up tearing the pump housing apart and making a new one out of stainless to bolt in. If I had to redo it I would have made the tank 2 inches taller and utilized something similar to this method http://www.vetteworksonline.com/ls1_conversion_fuel.htm

Since you mentioned prices, I spent about $150 on aluminum, $20 for the camaro fuel pump, $30 for other fittings and rollover valve(tanks inc), and $20 for the fill cap http://www.allensfasteners.com/detai...roduct_ID=9080

Here are links to my tank build
http://67-72chevytrucks.com/vboard/s...5&postcount=38
http://67-72chevytrucks.com/vboard/s...7&postcount=39
http://67-72chevytrucks.com/vboard/s...4&postcount=40

[duwem]

I do have an AC/DC tig and do know how to weld aluminum. I was thinking stainless since its a little easier to weld, and wont corrode like aluminum can.

Aprox how tall is your tank? Since I'm putting corvette suspension on my truck I dont want the tank hanging down too far and hiding it. Pumps may determine what heights I can use.

Thanks, that is a beautiful tank!

[hotrodrookie]

My tank is 8 inches tall with room to spare underneath. Most of the aftermarket under-bed tanks I have seen are 10" tall. Just make sure you have room above the tank as well if your going to have hose lines and fittings coming through the top so that they will clear the bed floor and cross braces. Don't forget to map out where your filler neck is going to be so that it clears stuff as well.

Stainless can be easier to weld and look very nice when done properly. If you have a sheet metal break then definitely use it. The more bends there are means the less opportunity for leaks and warping. If you can get all your fit up nice and tight you can most likely get away with fuse welding the entire outer shell together (not using filler rod)
Good luck, post pics!

[MrDude_1]

you can skip the baffles IF you run a modern EFI bucket style fuel pump arrangement.

this saves alot of work on your end, and takes the design issues out of it.

modern cars dont use baffled metal tanks.. they use blown plastic tanks, and have the pump in a "bucket" that keeps it submerged,even if the tank is near empty.

pics with links here: http://www.google.com/search?um=1&hl...&aqi=&aql=&oq=



that said.... your welding has to be up to snuff.. welding tanks is not easy or fun...
if you have a sheetmetal brake, use it to cut down on the number of welds needed...