[blueracecar]

i have an 89 gt that is a drag car only. right now it doesnt have a return line in the fuel system. my fuel cell has another port so i could add one if i want. i believe it goes just before the regulator and do you step the line size down or leave it full size? it has a 10 an hline on it now with an aeromotive 125 gph fuel pump and a barry grant regulator set at 7 psi (it has a carburetor). what is the purpose of a return line?

[EagleAutosports]

From a performance standpoint, return-style fuel systems have their good points... voltage is constant to the fuel pump, adjustable fuel-pressure regulators can be used, additional inline pumps can be added easily. But heat can become a factor in the efficiency of a return-style system. When recycled fuel is heated by the engine, exhaust and road-surface temperatures, or in-tank fuel temps, and if its temperature gets too high, another hot-fuel-handling problem usually arises- fuel-pump cavitation and vapor builds in the fuel lines. As we know, bad things happen when engines don't have fuel.
With a returnless system, since cool fuel isn't fed to the engine at all times, the standing fuel in the system also can become superheated. So, additional pressure is required to prevent fuel from boiling and vapor locking the system.