R-2 flapper vent

[jtjim]

The shop manual describes the function of the flapper type vent located in the air horn adapter cover as "opens when the engine is not running to prevent the accumulation of gasoline vapor within the air horn adapter assembly". I don't see any information as to how far off of the seat the flapper should be adjusted. Can anyone explain in more detail the function of this flapper valve. It seems that it should be adjusted so that it is very close to the seat so that the air pressure will close it without air pressure escaping. What is the danger if it is fully seated?

1967 Riviera, 1964 Avanti, 1953 Champion, Two Studebaker Gravely tractors

[fmarshall]

It only needs to be open. The spring tension is minimal. It just allows the vaporized fuel to dissipate after shutdown, because the engine gets hotter then, before finally cooling.

When running, the higher the RPM, the more the pressure. The flapper will close fully. And it needs to, so as to prevent fuel from decorating the engine compartment.

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63 Avanti R2, 4-Speed, 3.73 TT
Martinez, CA