There are three things you must align when installing a distributor: the drive shaft slots, the line for Number One piston stamped on the body of the distributor and the position of the rotor. To do this, start by rotating the crank pulley so that Number One Piston is at top-dead-center. Slip the rubber O-ring on the distributor's body and place it in the hole so that the tangs on the housing mates with the slots on the drive shaft deep in the hole.