The search for power puts emphasis on cramming more charge weight into the cylinders, but if it's not lit off effectively, the search fails. Having a good spark is paramount to performance, so starting with the basics, let's go through what it takes to get the best out of a set of plugs. The number one golden rule is 'don't run old plugs.' At mid to high rpm, most stock ignitions are more sensitive to mediocre plug performance condition than killer race systems. To emphasize the point Fig. 1 shows what a set of new plugs did to the Wide Open Throttle (WOT) output of a nominally 330 horse 8.8:1 small-block Chevy equipped with an 'as new' but stock HEI distributor. At low speed there was not too much difference, but as engine speed rose, and the ignition system's output dropped, so the difference becomes greater. This all relates to the ease with which a gap can be ionized. the temperature increases, it becomes easier to separate the electrons from the atom they are orbiting. Apart from simply being dirty, old plugs have eroded and have rounded surfaces, which are not good for spark initiation, but a sharp edge is.
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