When you're building a custom car, sometimes you have to think a little bit outside the box to get things working the way you want. For example, if you're building a lowered truck, the way you did the rear suspension might mean you have to move the stock gas tank, but it won't fit anywhere. Or maybe you have a muscle car and want a fuel cell in the trunk of a specific size or capacity. Either way, building a custom gas tank is an option if you're pretty handy with a welder. In this article, the gas tank will be a 2-foot cube, but you can build one to any specifications you want.
Lay the sheet metal onto a work surface and start to measure out the gas tank. The easiest way to get the cubic shape is to make two long strips of sheet metal that will bend into shape. Mark out two panels that are 2 feet wide and 6 feet long.
Lift the sheet metal into the shear with the help of your assistant, and shear the metal. Cut out the entire strip, which on the 4-by-8 sheet should give you three pieces: the pair of 2-by-6 panels and one that's 2 by 4 feet.
Measure and mark the 2-by-6 panels at 2-foot increments, so you have two lines across the shallow end of each panel. You're going to bend each of the pieces to form a U shape, with each side of the cube measuring 2 feet square.
Place one of the 2-by-6 pieces in the sheet metal brake so that the marking for the bend is in the seam of the brake. Then clamp the piece in the brake and bend it at a 90-degree angle to the table. Repeat this with the other mark on the piece, forming a U shape, with each bend forming a 2-by-2 square. Repeat the process on the other 2-by-6 panel.
Slide the two bent pieces of steel together so that the two U shapes form a cube. This is going to form a cube made completely of sheet metal, with no gaps or open panels on any side.
Put on the welding helmet and gloves, and begin to tack weld the cube together. A tack weld lasts about a second and goes no farther than 1/8 inch in any direction. This minimizes heat and warping on the panel. Place tack welds in the corners of the box, then in the middle of each seam. Keep the gaps in each panel to a minimum, because the tank has to be airtight when it's done.
Continue tack welding the panel, working your way around the cube frequently so that you don't heat up one side or another too quickly. Eventually, the tack welds will be so close to each other that it will look like one solid weld, which is what you want.
Grind down the welds using the grinder, making them look clean and neat. If you see any gaps in your welds, tack weld those so they close, then grind down the welds again.
Cut out the gas tank sending unit from the stock gas tank with the air body saw and air compressor. The stock gas tank has the sending unit bolted in a circular pattern to the tank body, and you want to remove that section to use it on the new tank. Try to make a square out of the metal so that it has at least 1/2 inch of clearance around the circular sending unit mount in the middle. In this case, the square is going to measure 6 by 6 inches.
Cut a 5 1/2-by-5 1/2-inch square out of the cube, preferably in the center of one of the panels. This is where you're going to weld the sending unit, and by having a small seam there, you can have a solid mounting surface and keep the tank airtight.
Place the cut-out square from the stock gas tank (and step 9), with the sending unit still attached, into the hole on the cube and tack weld the square onto the cube, just in the corners.
Unbolt the sending unit from the square that you just tack welded in place in Step 11. Use the 3/8-inch ratchet and sockets. Place the sending unit to the side.
Finish tack welding the square to the cube, using the same techniques you used to weld the cube together. Then grind down the welds.
Pour in the liquid contents of the gas tank sealer kit. Follow the directions to ensure that the gas tank sealer kit properly coats all sides of the interior of the cube. This will make sure that the tank won't rust internally.
Paint the outside of the gas tank with black spray paint.
Fill the cube with the gas foam cubes. They will stop the fuel from sloshing around in the tank, which means that if the tank runs low, you won't have sputtering problems with the engine.
Bolt the fuel sender into the cube using the 3/8-inch ratchet and sockets. The tank is now good to go.
