07-08-2019, 09:51 AM
Thanks Stuart
It was the common exh valve steel until about 1960. Has the merit of moderate expansion and hard stems. Cars so equipped required regular valve grinds and burned valves were common. Ritual almost unknown since. XB is magnetic. I dunno when XB originated but replacement exh valves for Sevens were often of lesser steels. (ie James VK+). Throughout use by my father and self, with pre XB valves my Seven needed a valve grind about 5000 miles. Other early hard users of Sevens report the same.
Presumably valves are now modern non magnetic material. I dunno what life is obtained in Sevens but remarkably superior. I found with Javelin cars XB valves short lived on weak mixtures, but modern valves unmarked, even with cracked valve seats.
It was the common exh valve steel until about 1960. Has the merit of moderate expansion and hard stems. Cars so equipped required regular valve grinds and burned valves were common. Ritual almost unknown since. XB is magnetic. I dunno when XB originated but replacement exh valves for Sevens were often of lesser steels. (ie James VK+). Throughout use by my father and self, with pre XB valves my Seven needed a valve grind about 5000 miles. Other early hard users of Sevens report the same.
Presumably valves are now modern non magnetic material. I dunno what life is obtained in Sevens but remarkably superior. I found with Javelin cars XB valves short lived on weak mixtures, but modern valves unmarked, even with cracked valve seats.