The coil pack is not capable of generating enough power (current x volts) to overheat and break an insulator. In order to generate heat from the tip of the insulator to the electrode (through the center of the insulator) you would have to have considerable current and some resistance. Since the center electrode is very low in resistance and the spark current is very week thereā??s just no heat, not to mention that the spark duration is so short that all the heat would be quickly dissipated. All the heat comes from the combustion chamber.
Cracked insulators are cause by a poor casting, miss handling during shipping or installation, excessive shock and vibration and excessive compression.
jeff
