Edelbrock Adjustable Bypass Fuel Pressure Regulator, Carbureted 

These fuel pressure regulators are machined from aircraft quality aluminum for those who demand the best. They have fluorosilicone diaphragm material for extended life and high temperature protection. Select regulators available with 1/8" NPT gauge port and a boost reference fitting for blow through or pressurized carb applications (even beyond 30 PSI of boost). Pressure regulation slope is 0.75 psi/gal of flow rate change. Will hold fuel system pressure for at least 20 minutes after pump shutdown. They are compatible with all grades of gasoline/methanol. Developed for optimum compatibility with Edelbrock Quiet-Flo fuel pumps. ALL regulators have an adjustable pressure range of 5-10 PSI.

This regulator is absolutely necessary if you are using one a PA fuel pump assembly with a carbureted engine