After rebuilding my heater valve and checking that the cable controls fully close the valve, warm air still vents into the passenger compartment when the heater box dampers are opened. Assuming the valve is working properly, warm air is leaking from the engine compartment and past the seal into the cowling area. Upon checking the seal, the cross section is not symmetrical. The flap is off-center and mine was positioned with the flap biased towards the rear, causing the flap to curl towards the front. I’ve reversed it to see if that improves the sealing, but if anyone knows if there is a correct bias for the seal flap (front or rear), please chime in. TIA, Ken