A companion to the shooters is a series of replaceable accelerator-pump cams. Holley pump cams have varied lift and duration profiles, just like an engine camshaft. The specific cams are color-coded, and each cam has two possible mounting positions. These positions change the duration of the pump shot. Holley recommends the pump discharge nozzle (shooter) be tuned first, then spend the time to fine-tune the cams. There is no "correct" cam for a given engine. Like the shooters, the pump cams require experimentation to determine which cam is best suited for your particular combination. Holley sells a pump cam assortment under part number 20-12.