Hiya all. Just thought I would share a fix I have just completed on my leaky air vent valves on my 56 vicky. The rubber seal on these things is sandwiched between two sections of sheet metal then spot welded in place inside the outer housings. Unfortunately the seal probably was not designed to last 50+ years!! Although you can drill out the spot welds on these valves and replace the rubber part (steel rubber products also have the shafts)before screwing or riveting the ***embly back together..... I took a slightly different route which works well. Process is as follows. Using hot candle wax carefully paint the inside of the housing (i used a 1/2inch wide brush and the bbq to heat the wax. Take care not to get any wax on the flap valve. Cut a spacer(i used a piece of rubber hose) and tape the valve almost closed. Apply a bead of silicon or urethane adhesive to both sides of the flap valve. Smooth with wet finger. Leave to set .This is the hard part(I suggest a week) so it is fully cured. Boil the kettle. Pour in hot water to melt out the wax. Done.