After approximately 500 hours I discovered during the annual condition inspection that the the back face of the flapper valve and the underside of the metal top of the filter air box are worn about half way through. I do not know what the failure mode will be except reduction in power when that interface wears through but I intend to coat one surface with Dow Corning 736 (red RTV) at this point to reduce the wear. The hinge is also badly worn and I am replacing it with a stainless steel hinge. There is also a small crack in the filter air box metal top at the fwd L/H edge of the heated air inlet opening that I am working on my repair for (some form of doubler probably involving extruded angle stock). Strong temptation to do away with the whole carb heat system but conscience prevails - so far. Time to sit back and think elegant fix thoughts.
Bob Axsom
Bob Axsom