Arcing across coil terminals

I'm going to repeat in a diferent way what I said earlier. There are only so many things that cause a coil to arc. OPENS in the secondary circuit. This includes bad rotor phasing, which leaves a big gap in the path from coil to plug, a bad coil wire or bad plug wire, or something wrong with a plug, such as internal break in the resistor, missing electrode, cracked, might even happen with weak coil/ boot insulation if you have a lean cylinder

WHAT IS THE common with all of the above? RISING SECONDARY VOLTAGE caused by an open. When properly connected, the spark voltage only gets "so high." If you disconnect a plug wire, example, that point is just like lightning, "looking" for a place to strike.

The second cause would be an insulation crack or chemicals on the coil, etc encouraging it to arc across at that point.