3 way valves?

I am trying to install a used kit on a friends car it has 4 3 way valves i dont under stand how they work on the valves 1 in on one side 2 out on the other when ou put air in the 1 side it will blow air out each hole on the other side depending on wire you use. 2 are set up like that the other two have 1 in and 1 out the other hole is pluged. Where is the dump valves? i dont under stand it was takin off a car working anybody have a clue?