The mechanical Chevrolet distributor is one of the main components in older style ignition systems used in the past. Between the 1990s and early 2000s, electronics began to supersede this part. Older models, however, still require them to function properly. The bottom of the distributor is a gear that is driven by the cam shaft in most models. The upper portion on the Chevrolet is where the cap, rotor and spark plug wires are located. This is the device that sends the electrical impulse to the spark plugs so your gasoline engine will run. The Chevrolet distributor is located on the rear part of the intake manifold on your engine. The holding bolt at the base needs to be loosened when the timing of your vehicle needs to be adjusted. The distributor is also the place where points and condensers can be found on cars that were made before electronic ignition. The reason a distributor should be replaced on your Chevrolet engine is due to the wear on the shaft or the gear at the bottom of it. Any imperfection in the rotation of this part will negatively affect the timing and performance of your engine. Routine maintenance of this part includes the placement of the cap and rotor on all models and also the points and condensers on the older models. Today the distributor on your Chevrolet engine has been totally removed and replaced by solid state electronics where the spark is controlled by your onboard computer. If a technician says they need to adjust your timing on the newer models without this mechanical part, then you can assume that they will be playing with the software in your computer. Be advised that this may void any manufacturer warranty, and you may want to get your car out of that shop before it is damaged.