Old metal sucks (AKA why I spent $2k on a custom-made fuel tank)

Part of my Pontiac project is adding electronic fuel injection (EFI) to the original 389cui V8, and this required a new fuel system as the old-style mechanical pump can’t supply the required pressure fuel injectors require. So, I needed a better fuel pump, and this led me on a merry course of failure and frustration as I discovered the original Pontiac fuel tanks are impossible to weld…

There are many ways to skin a cat when it comes to fuel system upgrades, and many use externally-mounted electric pumps with a surge tank (like another mini fuel tank) mounted either under the car or in the car. I generally find these noisy and smelly, so I am going to mount an off-the-shelf fuel pump inside my fuel tank.

I am using a commonly available VE-series Holden Commodore SSV fuel pump cradle (otherwise known as an “MRA”) which means I only have one fuel line running to the front of the car. Many cars have a return line, but mine does not require this.

To mount the pump I had initially decided I’d cut a hole in my original 54-year-old fuel tank, weld an off-the-shelf mounting kit to it, and then bolt the pump in. Simple, right? Not quite.

Here is the original 1964 fuel tank, with the new electric fuel pump unit and the mounting ring I needed to weld onto the tank to fit the modern pump. You can see the original sender unit on the ground in front of the tank. I was going to have to remove this to allow space for the new pump, so I was also going to have to weld up the original sender fitting hole in the front, too.

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When we pulled the tank out it was quite crusty as it had been sitting for years with stale fuel in it. I wanted to clean it out anyway, so I bought a fuel tank cleaning kit from KBS Coatings and then set about giving the outside a good scrub. 

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Unfortunately the cleaning products I used weren’t effective in getting rid of the scale and surface rust, so I got the tank media blasted instead.

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Once blasted I cut a hole to fit the pump. You can see how rusty and scaly the inside of the tank is in this pic.

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I welded up the original sender aperture and cut a larger hole to make it easier to fit the new pump around the ribs in the stock tank. Before I welded it up I thoroughly washed the inside with the KBS cleaning kit.

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The the inside cleaned up wonderfully with the KBS Aqua Klean and Rust Blast washes. 

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I coated half the tank with the sealant and left it to dry for a few days as it was easier to coat the bottom half of the tank through the large hole I’d cut. I wanted to weld the pump mount in, then coat the top half of the tank once I’d finished welding.

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I cut and folded up a flat insert which I could weld to the tank, then weld the pump mounting ring onto. It was at this point the wheels fell off the wagon. No matter how I tried the metal wouldn’t weld and would just blow holes through even on the weakest setting my MIG had. I gave it to an experienced welder who found the same issues, and suggested that getting a new tank made was going to be a far wiser investment rather than trying to re-engineer the old tank, which still had significant drawbacks to use in my car (no baffling to prevent fuel starvation/surging, etc).

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I went straight to Shaun’s Custom Alloy who used a spare original fuel tank I had as a template to create this new piece that would fit straight in where the old one once lived.  20180424_113127

Made from stainless steel it won’t rust like the old one or absorb fuel and chemicals, which means it can be modified later on if needed. However, Shaun also thought to add extra ports in case I decide to run a fuel return or even if I want to change where the tank vents from.

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The quality of the TIG welding is stunning!

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Shaun added baffles inside the tank to prevent fuel surge or starvation. 

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Shaun also TIG-welded this mounting ring on, which takes a rubber O-ring to seal. The pump bolts in here using 4mm Allen key-headed bolts. 

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I now have the rubber to join the filler neck to the tank, so once the neck is media blasted and powdercoated black I will get onto mounting the tank with some new custom hangers.

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