When building a race car, drag car, or just restoring a classic car, one of the most important items is the fuel tank. While there are companies that produce fuel tanks for every car on the road, it is very cost-effective to build a custom fuel tank for the project vehicle. The process of building a fuel tank is complex, but when performed properly, an aluminum fuel tank can last for many years.
Determine the size and shape of the fuel tank. Create a detailed sketch of the fuel tank complete with measurements and locations of filler neck, fuel pickup, and fuel level sending unit.
Measure and mark all panels for the fuel tank on the aluminum sheets. Mark the panels with permanent marker so they do not rub off.
Cut the panels out of the sheet aluminum. Cuts can be made with a circular saw fitted with an aluminum cutting blade or a reciprocating saw. Make sure the cuts are extremely straight. The straighter the cuts, the easier they will be to weld later on.
Locate the filler neck on the proper tank panel, and cut the hole with a hole saw or reciprocating saw.
Position the bottom panel and all sides in correct locations. Tack each side panel to the bottom panel, then to each other. Finish welding the panels in place.
Cut baffle panels for the tank out of the sheet aluminum. Baffle panels should be the full inside width of the tank and sit 1 inch off the bottom and top of the tank. Cut three 2-inch holes in each panel. If the tank is over 16 inches long, more than one baffle panel will be needed.
Position the baffle panel(s) in location and weld in place.
Locate the fuel pickup tubes and fuel level sending unit on the top panel of the tank. Cut holes for each. Then position the top panel on the tank and finish weld in place.
Install and finish weld the filler neck in place. Seal and install pickup tubes and level sending unit.
Allow the tank to cool from welding, then pressure-test the tank. To pressure-test the tank, cap the filler neck and plug one pickup tube. Fill the tank with air to no more than 20 PSI and spray all welded seams with soapy water. Look for bubbles. If there are no bubbles, slowly release the air. If bubbles are seen, those spots must be re-welded. When the tank passes the pressure test, it is ready to install.
