Pump cams are located on the throttle shaft. Remove the screws that hold the pump cam (or cams in the case of a double-pumper) in place. Note the location of the cam (position 1 or position 2), what the color is, and the type (standard 30cc or 50cc REO type). Installation is just the opposite. Keep in mind that pump cams designed for use with 50cc pumps are different from those designed for 30cc pumps. They can't be interchanged. Also, the big 50cc REO pumps never came standard on any production line Corvette carburetors.