[Tommy]

My car was equipped with a Holley Red (internally regulated) fuel pump. It worked fine for cruising, but was a problem at the track on hot days. This pump has a spring controlled valve that diverts fuel leaving the impeller back to the intake side of the pump when pressure to the output side exceeds about six psi. That means the same small amount of gasoline will circulate repeatedly through the impeller until the engine demands more fuel. Under the heavy demand of full throttle track use, the pump would get hot and the fuel recirculating through it would absorb enough heat to boil and cause vapor lock. I rebuilt the pump with a heavier spring to keep the diverter valve closed and added an adjustable fuel pressure regulator with a return line to the tank. This arrangement keeps fuel from staying in the fuel pump long enough to get hot and vaporize. .. I hope this helped answer your question.