Classic/Antique Car Repair: 1963 buick lesabre timing chain diagnosis, crankshaft pulley, buick lesabre

Question
in reply to distributar. yes it is a add on unit to stock distributar. but I had the same problem with the original points setup.I checked the play in the shaft it is whithin specs              thanks you  William R Bluhm

Answer
To check the timing chain for wear, remove the distributor cap. Use a wrench and turn the crankshaft pulley until the rotor moves. Mark the position of the rotor tip onto the distributor. Next make a mark on the front pulley to the engine block. Now with the wrench turn the pulley slowly the opposite direction until the rotor just moves. If the marks on the pulley are more than 1/2 inch apart, the chain is worn and stretched and need attention. Less than 1/2 inch it is ok.
Brad