" cylinder heads with breaks between the valve seats or between clapper seat and the Zuendkerzgewinde can be re-used without reduction of the life span, if it concerns easy, max. 0.5 mm broad incipient cracks or if only tore the first courses of the spark plug thread. " I did the opposite (english to german) for spark plug, and got "Funkenstecker". I don't know what "Zuendkerzgewinde" means. Ken