Thanks Erik for your kind reply.
The valves are 3/4″ outside diameter. The castleated boss that holds them in looks cycle thread 26tpi. What size and thread are the bolts you have used?
If I turn down a thin copper blank about 20 thou thick and place it between the valve, up against the cylinder wall, tighten down as tight as I can, as far as I can see I will make the valve inoperative and should have an gastight seal. Am I right or have I overlooked something?
My professional background is nursing and I am afraid that my engineering skills are in there infancy.
Cheers lads
