I usually went to the race track with at least two, or sometimes three sets of clean spark plugs. After practice laps, we would check the color of the plugs and adjust the fuel mixture accordingly. If a second mixture change was needed after more laps, the third set of plugs were used for the night's racing. During the week, all the plugs would get glass bead blasted and used again for the next night of racing. With a few sets of AC commercial plugs with the heavy duty electrodes, the same plugs would usually last half a season or more.
Jerry
