The fuel pump tries to overcome the g-forces created as the car accelerates. In most cases, steel tubing fuel lines work quite well; other options are aluminum tubing or steel braded fuel lines. Rubber fuel hose should only be used in areas where its flexibility is needed. When designing a fuel system, always follow the fuel pump supplier's recommendations for fuel line size, fuel tank supply, and venting lines.
The fuel lines are like blood vessels. If they are not allowing proper flow, nothing else
Fuel Tank Venting
Always check and set the fuel pressure at the carburetor, and pay attention to fuel tank venting. For every gallon of fuel pumped out of the fuel tank, a gallon of air is drawn in through the fuel tank's vent system. Always use some type of filter in the fuel tank vent system in order to avoid dirt and debris coming into the fuel tank. Place the vent inlet in a "clean" and dry area, not in the wheelwell where water, rubber, and debris from the tires is always flying around. Often when taking a carburetor apart for a jet change, dirt and rubber are found in the fuel bowl. This debris may have gotten into the fuel system through the fuel tank vent.
A filter in the fuel tank vent system can help prevent a carburetor jet from becoming plugged by this debris, but always keep fuel safety in mind. Use a check valve in the vent line to avoid fuel spillage in the event of an accident. We have also seen many vehicles in which the vented fuel cap does not allow air into the fuel tank as quickly as the fuel is pumped out. Consequently, a vacuum was created in the fuel tank, causing the fuel pump to starve for fuel. The fuel pressure would then drop to less than 2 pounds under sustained high-load driving conditions. The cure for this problem was to add extra fuel tank venting.
Filters for the fuel system are important and often neglected. The apparatus must filter the fuel in order to keep any debris in the fuel tank out of the carburetor, yet not present any restriction to proper fuel flow. A dirty or neglected filter can restrict the fuel flow, causing the engine to run lean due to a lack of fuel volume.
All fuel filters are not the same; some can filter finer particles than others. Filters are also designed to move a certain number of gallons per hour of flow. If the filter offers too much resistance to the flow of fuel, the fuel pressure will drop at high fuel flow conditions, and the carburetor or fuel injectors will starve for fuel, causing the engine to lean out and create possible engine damage.
A Problem-Free Fuel System
A well-designed fuel supply system with the fuel tank, vent system, fuel filters, fuel line size and routing, fuel pump, and fuel pressure all matched to each other and the engine's fuel demands will help make tuning a race engine easier and avoid fuel system problems on race day.