The distributor of a typical engine has a lot more responsibility than just distributing the spark to the correct cylinder (which in itself is a feat). It is also triggers the coil to release the high voltage, in many cases it turns the oil pump, it distributes the spark to eight different cylinders and it alters the timing of the system. The distributor could be the hardest working part of your ignition system and this is why it is important to ensure that your distributor is up to the task of delivering the performance and power that you expect from your engine. Distributors have changed over the years. From plastic to billet housing materials, trigger mechanisms, timing controls and other items have all been modified over the years, yet most models will perform some if not all of the following duties:

• Distribute the spark to different cylinders
• Trigger the secondary side of the ignition
• Alter the ignition timing
• Driving the oil pump

Most distributors are driven by the camshaft through gears with a one-to-one ratio. (This means the distributor turns at camshaft speed, or half of crank speed.) There are a two important parts attached to the shaft; a trigger wheel and the rotor. The trigger wheel will vary depending on the type of trigger being used, but you will notice that it will have a tooth, or lobe or space for each cylinder of the engine. The rotor delivers the high voltage from the coil to the correct cap terminal. When the coil fires, the voltage is transferred through the coil wire to the center terminal of the distributor cap. This terminal contacts the center of the rotor, moves across the rotor and jumps across a small gap to the spark plug terminal of the cap. All of this occurs in fractions of a second and thousands of times.

Common Firing Orders for Domestic Vehicles