Fuel Pressure Regulator By-Pass Style 6psi

The Holley Fuel Pressure Regulator By-Pass Style 6psi (part number 12-881) is a die-cast in-line fuel pressure regulator designed for gasoline-fueled engine systems requiring reliable pressure management in the 4.5 to 9 psi operating range. This bypass-style regulator maintains consistent fuel pressure under varying engine loads, protecting fuel injectors and carburetors from pressure spikes while ensuring stable supply during acceleration, idle, and cruise conditions.

Built from aluminum construction with chrome plating, this regulator features 3/8-inch NPT inlet and outlet ports for industry-standard fuel line connections, plus a 3/8-inch return port for excess fuel bypass and a 1/8-inch NPT gauge port for pressure monitoring. The bypass design automatically diverts excess fuel back to the tank when system pressure exceeds the regulator's setpoint, preventing fuel system overpressure without requiring external electronic controls. Weighing just 0.69 lbs, the compact 3.7 x 2.7 x 3.7-inch form factor allows flexible mounting in engine bays with space constraints while maintaining accessible gauge and return connections.

This regulator is ideal for classic carbureted engines, fuel-injected street vehicles, racing applications, and restoration projects where OEM fuel pressure management is either absent or unreliable. Builders and technicians rely on bypass regulators to eliminate vapor lock, smooth out erratic idle quality, and protect fuel system components during high-load operation. The adjustable 4.5–9 psi range accommodates both low-pressure carburetor systems and higher-demand fuel injection setups, making this Holley regulator a versatile solution for gasoline engines across multiple platforms.