The heat exchanger/cylinder head gasket on no. 3 cylinder just blew and has been replaced (1971 1600 stock engine and exhaust). Now the one on no. 1 cylinder sounds like it's on the way out. My theory is that the heat exchangers were wiggled when the exhaust box was replaced. I've got a round trip to Pembrokeshire of 600+ miles planned for the weekend and no chance of getting it fixed beforehand here in Brighton. If I drive it blowing will I do any serious or long-term damage? Or if the worst comes to the worst does anyone know of a good aircooled mechanic along the M4 or in South Wales?