diy fuel tank

[NId4x4]

After a reecent inspection of the fuel tank on my 72 Jeep comando, I realized a new tank is needed imediatly. After some shoping around I found stock replacements, poly replacements, and some heavy duty replacements, none of which i felt like were a good deal. So i have decided to build my own.
Requirements:
Skid plate botom, sturdy enouph to support the weight of the vehicle, extra fuel capacity (25-30 gal would be great), can't effect departure angle. I currently run an in line holley pump, but am considering an in tank? I like the servicability of the inline, but from what I have seen the in tank pumps offer a better service life. Oppinions?
Abilities:
I am a compotent welder with both mig and tig, and I have access to both welders and plasma cutter, an iron worker, and a break.
Questions:
What materials? What general shape, most importantly for the sump? What postioning for the fuel pick up?
Any ideas or advice would be greatly apreciated. Thanks in advance!
:sombrero:

 

[R_Lefebvre]

Materials I'd think stainless steel, or aluminum. Mild steel would rust inside, or you'd have to coat it or something... meh. With stainless, you'll have to back-purge the inside with argon while you weld the outside, so it will be a bit harder. SS will be more resistant to tearing on sharp rocks, aluminum will be lighter and easier to work with.

The shape doesn't matter too much, as long as it fits. Best to have a sloping bottom if possible to the pickup at the lowest point. This should all be obvious.

 

[cyclic]

Don't forget baffles, a drain plug, and enough connections to hook up fuel injection in the future. You my never inject it, but having the ability to do it just be removing a plug or two will be priceless in the future. Also some beads or ribs in the flats will considerably increase strength of the tank. Most will do a small sump where the fuel pick-up and drains are located. Keep ing the external pump is your best bet, makes for much easier repairs.

 

[ntsqd]

There are several quality tank coatings intended for use in fuel tanks. I wouldn't let the rust issue steer you away from steel, just budget for the coating after the tank is built. A friend has had the POR-15 product in one tank for going on 15 years with no issues.

Baffles are mandatory. Unless you're going to make the top removable don't bother thinking about fuel cell foam to control slosh. The foam has life expectancy of about 5 years. Design a "pocket" in the baffles for the fuel pick-up that will hold a quart or two at any reasonable vehicle angle. Make the design such that it is allowed to re-fill fast when the vehicle is at a normal angle. Small shadow and tall is usually the key there.

Investigate how home-built aircraft guys make their fuel pick-ups. I'd suggest something along those lines, perhaps wrapped in a SS straining mesh and maybe not. Even though you've coated the tank or made it from something that doesn't easily corrode doesn't mean that you won't get rust & junk from the fuel stations. I think that it is the FMVSS that requires all OE tank connections at the top. Not a bad idea to follow if possible.

 

[R_Lefebvre]

Do the plastic tanks have baffles? I don't think so.

 

[ntsqd]

Their sumps are usually built into the fuel pump/pick-up assembly. Baffles are less necessary there. In a metal tank the baffles also add structural strength, particularly important to a tank with a built-in skid-plate that might see use. I liken building a off-road intended metal tank w/o baffles to building a road race/Solo oil pan and leaving the baffles/gates out of it. Either will leave the engine starving for something.

 

[R_Lefebvre]

Their sumps are usually built into the fuel pump/pick-up assembly. Baffles are less necessary there.

OK, that's what I thought.

I've been building a skidplate for my plastic tank. Doing so is making me think... maybe I'll just do a new tank with integrated skid in the future. It would probably weigh about the same as what I've done now. No promises on the timeframe though. Maybe next winter.

 

[NId4x4]

Thanks for the ideas so far. As budget is always an issue for me I am definatly not rulling out mild steel, but would the cost of the coating off set the price of ss or aluminum? What would be your suggestions for material thicknes for each, 1/8 in side and 1/4 bottom for steel, or what do you think? Also do you think i kneed baffles in both directions. What about a swinging pick up like some oil pans use, is there even such a product. As far as shape i was refering to weather the low part, or sump should be front midle or back, the latter of coarse doesn't lend its self well to departure angles. Lastly I am running a 670 holley projection system with the inline electric pump right now, if memory serves it requires 14 psi.:chef:

 

[RocKrawler]

When I used to build custom steel Samurai tanks I used 1/8: top & sides, 1/4" bottom and a single baffle (side to side). It was insane overkill, but as part of my marketing I parked the Samurai on top of it to prove its strength, and a floor jack underneath in another pic lifting the entire vehicle by the tank with zero deflection. They sold out instantly and never needed a skid plate. Sump had a small pocket built around it to avoid total starvation when near empty, and an extra in line fuel filter/accumulator will help against starvation as well: http://www.bcbroncos.com/fuelcarb.html (scroll to the bottom of the page)

 

[R_Lefebvre]

RocKrawler, are you talking steel or aluminum?

NId, I'd suggest just going with aluminum. I just finished making a gas tank skidplate for mine out of steel. 12ga sheet, and 1x2 box tube, and it turned out heavier than I'd like, though it's pretty strong.

Maybe next year I'll just rebuild the whole thing. I'm pretty sure I could make a gas tank with integrated skid out of aluminum for the same weight as this skidplate.

 

[ntsqd]

The POR-15 product is $46.50 for the one quart sized kit.