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Hard Cell

Alloy drop tanks and fuel cells have been around for decades in race cars, boats and planes. Building a custom fuel cell for any application brings a range of benefits over the any standard tank. Perth Street Car visited Torque Fabrications, in Bellevue, to witness a new tank being fabricated.

The old steel tank was from a 1984 Corvette and the owner required a new fuel cell to be fabricated for a number of reasons. Most important of all was for extra fuel storage capacity. The car will soon be used for both street and competition and the removal of the spare wheel (which normally sits directly under the tank) has allowed a new tank to be produced to take full advantage of this extra room.

Scott, from Torque Fabrications, literally started with a clean sheet of 4mm aluminium, taking dozens of measurements from the original tank before scribing, cutting and bending the plate to form the basic shape of the new tank. After building countless fuel tanks for boats, Scott is well aware of what the authorities require in terms of the design and construction of an accredited fuel tank for a vehicle. Points like no right angle bends and pressure testing of every inch of weld are essential.

Once all the panels are cut and bent into shape they can be tack welded into position. This gives a great impression of what the finished item will look like but it also allows critical dimensions to be checked before the time consuming task of final welding is undertaken. At this point it is important to design and install the internal baffles which control fuel movement, or surge, inside the tank under hard cornering, acceleration and braking. The baffles sit either side of the main fuel pickup and trap fuel to maintain a constant supply to the pump under all handling conditions. At the base of each baffle is a small “mouse hole” which allows fuel to flow into the cavity from the rest of the tank.

That brings us to another advantage of a custom made cell. Apart from preventing fuel slosh, which is a huge problem with factory tanks, it also allows a much larger diameter pickup pipe to be installed. This is critical with high horsepower carburettored cars in particular, where a large volume of fuel is required in the entire line from tank to bowl. In this case a ½-inch pickup tube and ½-inch return tube have been welded just underneath the two threaded holes in the top of the cell. The factory filler neck has been retained, with its integral breather pipe (which features a one-way valve).

Another benefit is the use of a quality aftermarket fuel sender. The sender is connected to the fuel gauge and lets the driver when it is time to fill up or start thumbing a lift. Many older cars have floats on the end of their factory senders that become porous or leak over many years. The end result of which is that they sink and the needle becomes permanently stuck on E for not enough. A new VDO sender was fitted to this tank and provides a wide sweep from around 100mm from the bottom to just below the top.

After the baffles are welded into place, the outer seams of the fuel cell can be fully TIG welded for a very strong and great looking weld that says “race car” from 10-metres away. The finished tank will sit in the factory location in the Corvette but now the bulk of the fuel stored in the car will be much lower in the car thanks to the deeper bottom of the new cell. This lowering of the fuel mass will help the car’s handling characteristics too. The finished tank is then stamped with an identification marking to inform anyone inspecting it, who is was built by, when it was built and that it was fabricated by an accredited workshop.

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