Most "racing" spark plugs are just colder heat ranges of the same street versions spark plug. Their internal construction is no different than their standard heat range equivalents. Racing spark plugs do not make more power in an engine, rather, they allow the engine to make more power. Meaning, after all the engine modifications are done that add power, a racing plug is better designed to operate in the torturous conditions created by those modifications. If you used a regular plug in a modified race engine, it would quickly be destroyed, while a properly selected racing plug would endure the extreme limits of that motor. Take that same racing plug, however, put it in an unmodified motor, and it would foul out within minutes.
The differences between a racing plug and traditional plug are not solely heat range. There are firing tip configurations necessary for survival in alternate fuel racing and situations of extreme boost/compression (such as retracted-nose insulators or surface gap firing tips), which would run very poorly in an unmodified motor. However, there are some very effective race plug design features including ultra-fine wire electrodes, gold palladium, platinum, iridium electrodes and cut back ground electrodes that are now available in standard non-racing heat ranges, these can maximize fuel combustion and improve performance in unmodified motors as well.
