An extension-type spark plug includes an upper terminal stud and a lower terminal stud axially spaced from one another in electrical communication with one another. An upper tubular insulator having a through cavity surrounds at least a portion of the upper terminal stud. A lower insulator constructed of a separate piece of material from the upper insulator has a through cavity surrounding at least a portion of the lower terminal stud. A spring member is disposed between the upper terminal stud and the lower terminal stud and biases the upper terminal stud and the lower member away from one another. The spring member allows the upper terminal stud to move axially under an externally applied force sufficient to overcome the bias imparted by the spring member and maintains electrical communication between said upper terminal stud and said lower terminal stud.