Too Much Gap: Excessive spark plug gaps could cause your race motor to not reach maximum potential power. To check if the spark plug gap is too much, simply the pull spark plug boot off and look at the spark plug ceramic insulator, if you see a bunch of gray lines lengthwise it's time to reduce the gap.
Racing Plug Gaps: For most high performance aftermarket ignition systems a .050 inch spark plug gap usually works fine. If you are running a supercharger or turbocharger you would run a spark plug gap of .035 inch or less due to the higher cylinder pressure. Remember that the greater the cylinder pressure the more resistance the spark has to overcome so the gap has to be smaller.