Thread diameter: .157"
Power Piston Metering Adjustment Screw allows adjustment of height of primary metering rods within the primary jets. Great for fine tuning your Quadrajets APT cruise Air/Fuel metering.
Spring #2021C is required under adjustment screw. (Sold separately)
Before removing original power piston adjustment screw, turn screw in clockwise, counting the number of turns, to lightly seated position. Then return screw to original setting.
If original setting is unknown, set adjustment screw to approximately 3.5 turn out from its fully seated position.
Not for use in electronic feedback carburetors with mixture control solenoid.