making fuel tank

[PJ.zook]

Has anyone made theyre own fuel tank for a sierra? What is involved?
From what i can gather, you need a filler hole, a large breather fitting at top of tank somewhere which leads up to top of filler cap so air can be expelled while filling, and then some kind of expansion fitting also on top which goes to the carbon canister. The expansion fitting im thinking of fitting to a tank im designing, should it only be a tiny hose, like 2 or 3mm to stop fuel sloshing up it when 4wding? Or even have its own tiny welded box ontop of the tank, which is connected to the tank by a 2mm drilling thru so gas can get thru, and sloshed fuel can too but can drain back thru without being sucked into hose (which hose is attatched to this separate small box ontop of tank), does this sound right?

[Gwagensteve]

What are the level of your fabrication skills? The biggest problem with building tanks is clean, leak free welds.

Replacing the factory breathers etc is the easy bit - just copy what is there. Welding the corners is a bit of a problem - taking a hit on the corners where you have a weld is the issue. If you have access to a box folder, a guillotine and can mig, or preferably tig well, it will be a pretty straight forward job.

Have a think about clearance though - sierras are very tight between the tank and the rear shocks, and the exhaust. If you have the skills to build a tank, then you have the skills to move the mounts, build a new shock mount crossmember and exhaust and build a tank with around 70-80l capacity and no loss of clearance.

Steve.

[CRUSHU]

You will also need to add baffles to the tank.
Basicly, partition the tank internally in 2 - 3 places, with say 50mm cut off the lower corners of the partition.
Build a swirl pot in there as well, useful for carby engines, but nessesary on a EFI engine, should you wish to convert later on.

[PJ.zook]

Yeh im pretty good with the TIG, and i was gonna run a bashplate so bashing the tank anymore shouldnt be a problem. Im also going to reroute the exhaust too so that wont be a problem.
Basically i want more capacity, and i need to replace my old tank anyway as ive bashed the bejeezus out of it.
I was just going to make a simple one or maybe use another old one, then use the engines lift pump to keep a 1litre swirlpot under the hood full and have a Bosch high pressure pump supply my injectors (custom efi).
Maybe if i build another tank i can have an intank pump hmm

[benjamin78au]

wondering what the cost on making one would be.

As i have the muffler beside it and bneed a bigger tank.

bj

[andrew e]

You will also need to add baffles to the tank.
Basicly, partition the tank internally in 2 - 3 places, with say 50mm cut off the lower corners of the partition.
Build a swirl pot in there as well, useful for carby engines, but nessesary on a EFI engine, should you wish to convert later on.

Are baffles necessary? the reason i ask is i have seen a tank crack where the baffles have been welded. Not Home made tank, a very common aftermarket brand one.

Andy

[jcclures]

I am no expert but I have made a few tanks for my, and my friends, 4x4. When I have made my tanks I have always folded the baffle with a 25mm fold and welded along the edge of the fold this lets the tank move and not pull the weld, I have had tanks which I have made which are still in use 18 years later with no problems.

[jcclures]

I weld the edge of the sheet to the tank, so the fold works like a hinge and allows the tank to expand without the weld pulling causing a leak.

[matthewK]

if you have the welding skills talent and the get up to do it shouldn't have any trouble ,

the only things to consider is i guess pressure testing for leaks

heat sheld from muffler and bash plate

and certificate of approvel that the tank meet australian standards

[awill4x4]

I am no expert but I have made a few tanks for my, and my friends, 4x4. When I have made my tanks I have always folded the baffle with a 25mm fold and welded along the edge of the fold this lets the tank move and not pull the weld, I have had tanks which I have made which are still in use 18 years later with no problems.

That's exactly the same way we do them at work, it allows a fraction of movement without tearing the welds through the tank shell.
Regards Andrew.