Holley makes the best low-pressure fuel pressure regulators we have found. It helps to ensure a constant, steady flow of gas to the carburetor regardless of variations in fuel pump output pressure.
The 4-9 psi model is preset to approximately 6.5 psi. With the aid of an accurate pressure gauge, it can be easily adjusted as required within its specified range.
There is one inlet port (bottom) and two output ports (side) to aid the connection of multiple carbs. Alternately, single carburetor applications can use the remaining port for a fuel pressure gauge. All of the ports are 3/8 NPT female.