A small diameter spark plug configuration is provided, the configuration has been found to provide additional volume for the insulator member. That is, by limiting the overall number of threads on the intermediate portion along with a limit of the overall diameter of the spark plug, additional volume of insulator material may be achieved in an interior cavity of a metal shell of the spark plug. This additional volume enables a portion of the insulator member to have a larger diameter and hence greater material thickness. The larger diameter of the insulator provides enhanced dielectric properties and protects internal components of the spark plug from high combustion chamber temperatures while simultaneously providing a robust attachment of the spark plug with an engine head.