Dwell angle is the amount of time, measured as degrees of rotation, that contact breakers close in a distributor. Unless dwell angle is accurate, ignition timing won’t be accurate. The period, measured in degree of cam rotation, during which the contact points remain closed is called the dwell angle.

Too wide a point gap decreases the dwell angle. This does not give the coil sufficient time to charge, resulting in a weak spark. It also slightly retards the timing. In short, either too wide or narrow a point gap will cause a misfire under load.

Typically point gap settings average around . 015 inch for eight-cylinder engines and . 025 inch for six- and four-cylinder engines.

By examining the insulator firing nose color, an experienced engine tuner can determine a great deal about the engine’s overall operating condition. In general, a light tan/gray color tells you that the spark plug is operating at optimum temperature and that the engine is in good condition.

CONTACT POINTS – The contact points, also called breaker points, act like spring-loaded electrical switches in the distributor. Its function is to cause intermittent current flow in the primary circuit, thus causing the magnetic field in the coil to build up and collapse when it reaches maximum strength.

The CDI, being “solid state” tends to be much more reliable and fairly maintenance free as compared to breaker point ignition. CDI also provides for more precise coil primary “switching” that results in a fully saturated winding and hotter spark due to the longer “dwell” afforded by the nature of the system.

An ignition coil (also called a spark coil) is an induction coil in an automobile’s ignition system that transforms the battery’s voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel.