MSD Ignition MSD3737 Iridium Spark Plug 15IR4 Resistor Type (Gasket Seat. 14mm x 3/8" with 13/16" Hex)

MSD's spark plugs are engineered to improve the efficiency of the combustion process to create the most power possible combined with increased durability. The center tip of the plug is made from iridium to promote the best spark and increase resilience. A proprietary ceramic material enhances the dielectric strength of the plug housing forcing the spark, even under extreme cylinder pressures, to jump across the plug gap to the ground electrode. This electrode is machined to expose more spark to the incoming gases to promote the most effective combustion event possible.

• Proprietary plug design inside and out
• Designed for use on high performance vehicles that utilize high output ignition systems
• Machined electrode increases exposure to the flame to improve combustion
• MSD's proprietary ceramic formula provides the highest dielectric strength
• Yttrium ground electrode reduces the chance of pre-ignition
• Iridium tip improves cold starts
• Designed to outlast other performance plugs on the track or on the street
• All spark plugs tested prior to packaging and shipping
• Shorty-style plugs for applications where space is limited

What makes MSD's Iridium plugs a cut above the competition? Besides MSD's race winning experience of firing 330 mph top fuel cars, the endurance of 500 mile stock car racing and the brutal expectations of off-road racing, our new spark plugs are designed to perform from the inside out.