How to check distributor cam wear with a timing light

How to check distributor cam wear with a timing light
Article/picture from Equus Tech Tips  http://www.timinglight.com/resource/techtips.cfm

Perform this test after the timing has been set and the timing mark lines up with the reference pointer for the No. 1 cylinder.

Connect timing light to spark plug wire directly opposite (180 degrees) of the No. 1 cylinder on the distributor cap.

Start engine and aim timing light towards timing mark. Reading should be the same as when timing light is connected to the No. 1 cylinder. (Timing mark should line up with reference pointer).

If reading IS NOT the same, you may have a worn distributor cam or bushing, or a bent distributor shaft. Repair as necessary.