In olden times, part of the ritual of changing your engine's spark plugs was making sure that the gap was set correctly for optimum performance. That is, the distance between the spark plug's center ...

Spark plug wires need to be connected in a specific, sequential order, called the firing order. Spark plugs firing out of sequence will cause an engine to backfire.

A hot spark plug has a longer insulator tip and less insulator-to-shell contact area. Thus it absorbs more heat from the chamber, and transfers less to the cylinder head coolant.

High-Performance Spark Plug Selection Can Be Boiled Down To Four Basic Steps ... Controlling the operating temperature of the plugs firing tip is the single most important factor in spark plug design.