Indexed spark plugs align the open end of the electrode toward the intake port. The hottest flame meets the new fuel charge for a performance gain, increases fuel mileage and plug life. This is a speed secret car racers have used for years. You simply mark the electrode side of the plug with a magic marker on the porcelain. You then shim the plugs with the washers to align the electrodes toward the intake ports. Fits 14mm threaded spark plugs.

• Indexed spark plugs align the open end of the electrode toward the intake port
• The hottest flame meets the new fuel charge for a performance gain, increases fuel mileage and plug life
• This is a speed secret car racers have used for years
• You simply mark the electrode side of the plug with a magic marker on the porcelain
• You then shim the plugs with the washers to align the electrodes toward the intake ports
• Note: Fits 14mm threaded spark plugs