Edelbrock 12645 HDQ Power Valve

Standard Flow Single-Stage Power Valve - 4.5" Hg The Edelbrock #12645 Single Stage 4.5 Hg Power Valve operates by using engine vacuum to control the opening and closing rate. During heavy load or under full power situations, they open to supply additional fuel to the main system to eliminate hesitation and bogging, ensuring the smooth delivery of power without any drivability concerns.