Arcing at distributor

Whenever there is an open in the high tension circuit, you get arcing. Such things as burning the electrode off a plug, an plug that is cracked, bad connection ANYWHERE "in the chain" including the coil, dist. center tower, problems with the rotor, on and on.

Take all the wires.......including the coil, and clip your ohmeter to each end. "Shake" them while connected which will help show up "bad spots" in the length of the wires. Gently move the ends looking for drastic changes in the meter reading. "The old rule" of thumb used to be that a good wire was less than 1000 ohms per foot of wire. Almost any newer wire I've come across is far below that reading.

Other things that can cause arcing is such things as a bad cylinder.......burned / open valve, causing a lean condition, or a bad intake vacuum leak causing a lean cylinder