A mechanical pump lives off the camshaft eccentric, so it only makes pressure when the engine turns, which is exactly what a carbureted street engine wants and why there is no relay or wiring to fail. This one runs an aluminum housing with 3/8 in. NPT ports at both ends and tops out at 6.0 psi, in the window a four-barrel float valve is designed to close against.

Edelbrock 1721 Performer RPM Fuel Pump Specifications:

• Mechanical pump for gasoline, 6.0 psi maximum pressure.
• Fits small-block and W-Series Chevrolet engines, covering 1955-1987 Buick, Chevrolet, GMC, Oldsmobile and Pontiac.
• Aluminum housing, single inlet and single outlet, both 3/8 in. NPT female.
• Gasket and mounting hardware included.
• Intended for carbureted applications. Not for fuel injection pressure requirements.