Designed for use in Engines with Higher-than-Stock Cylinder Combustion Pressures, these Ford Racing Modular 3-Valve Spark Plugs are prefect for your Ford. Their unique Design is proprietary to Ford 3-Valve Engines and they are only available from Ford Racing. The Ford Racing modular 3-Valve Spark Plugs are one Heat Range Colder than the OEM Ford Mustang GT, and Two Heat Ranges Colder that the Stock 5.4L Truck Engines. Keep your Engine Firing on all Eight Cylinders with a Set of these Ford Racing Modular 3-Valve Spark Plugs.