Fuel tank modifications?

I am seeing, on the internet etc, more people modifying fuel tanks to suit aftermarket EFI fuel pumps (fitting pumps with built in swirl pots to old style non efi tanks. Last night I watched an episode of the Castlemaine Rod Shops modification of a HK-HG Holden Station wagon and they had to modify the tank twice. With the closure of Automotive manufacturing, and subsequent total loss of Holden, getting parts for the older vehicles is not just getting harder but what is available has gone up in price. I have been looking at larger fuel tanks for my VC and VS Commodores but find the prices to high and in the case of the VS wagon you can't get an extended range tank anyway. So I thought I'd ask what type of sheet metal would suit a fuel tank in these older cars and just clarify if TIG is the appropriate weld to use?

Before anyone says something like "don't do fuel tanks, it's dangerous" I appreciate your concern, safety is always the first thing on my mind when working on anything but I'm in the situation where I need long range tanks and am researching the best material to use. GMH made the original long range tanks by cutting the bottom half about an inch below the flange and inserting a strip between the 2 halves of the bottom of the tank to make the bottom half of the tanks larger. Even though the original tanks never had fuel in them when this was done and mine have obviously had up to 40 years worth of fuel run through them the process will be the same. The tanks will be thoroughly cleaned inside and out, with the VS tank getting a much needed new return line fitted before reassembly, and purged with inert gas.

This won't be done anytime soon but is a job on my todo list. I will practice my welding skills on other jobs before I take this on. I am researching the best materials to use so I am able to practice before I do it.

If you're modifying a tank yourself, it may be a good idea to chat to the certification folks as I expect it will need certification.

With the GM fuel tanks, they will have been a compromise using stampings they already had on hand. If I were you, I'd look at designing, and fabricating, one from scratch to make best use of the available space. It 'should' be safer and may be more acceptable if certification is required, you can add additional baffling, sumps, fuel pickup/returns, etc as well.

I can fully agree with the desire to do it your self, but there are other options - I had a quick look on-line, and there are still companies that sell the factory tanks, in varying condition, but $$$s* - and there is apparently a difference between beam and IRS rear suspension tanks.

An intermediate step might be to check out the wreckers for a V8 tank, as they're supposed to be around 20 litres larger in capacity?

*there is quite a bit of interest in this, as some of these links suggest, and may give you some ideas.

https://forums.justcommodores.com.au/threads/long-range-fuel-tanks.19145/

https://forums.justcommodores.com.au/threads/long-range-fuel-tank.44233/

https://www.gumtree.com.au/s-ad/essendon/wrecking/holden-commodore-83l-drop-tank/1112914591

http://aberfeldie.australialisted.com/3040/car-parts/holden-commodore-80l-drop-tankdroptanklong-range-fuelvlvnvs_17945065.html

JZ Custom alloy make tanks for some aussie vehicles, as does Brown Davis - but they seem to just have ute tanks - may be worth a call as, if they can't help, they may know someone who can.

Hi Gordon, thanks for your post.

It is possible the tank will need certifying. The VSI (https://www.rms.nsw.gov.au/documents/roads/safety-rules/standards/vsi-06-light-vehicle-modifications.pdf) is deliberately vague on this point. You might read it and think it isn't but the wording most certainly allows for fitment of parts that were considered an "option" on the model range. If certification is required it would only be on the VS and that would be the case for any non-oem tank as well.

A V8 tank may be an option for the VC but the VS is a station wagon and all station wagon tanks are the same size. I have communicated with the guy who sells the long range tanks on Gumtree, Chris started the business but his father Paul now does the work. It is probably more cost effective for me to modify the tanks I have rather than pay through the nose for something someone else has steam cleaned and painted.

Brown Davies only build ute tanks for Commodores now, from memory they used to do Commodore sedan tanks many years ago. Never heard of JZ until now, just looked that his FB page looks like nice work but the same pictures used in multiple posts over a few months.

I'd still prefer to know what material is used and when I am comfortable with my own welding skills I'll do it myself.

I have attached a pic of a genuine 90 litre long range Commodore tank, see how the tank has had a few inches spliced into it. This is what I am researching.