Reed Valve System (Federal)
Reed valve is a special, one-way flow control valve. Reed assembly opens and closes with exhaust system pressure pulsations (which are normal action of engine combustion cycle). When atmospheric pressure of intake fresh air is higher than exhaust pressure (negative pulse), reed valve is open to allow fresh air into system. When exhaust system pulse is higher than intake air pressure (positive pulse), reed valve is closed so exhaust gases cannot back into intake air source at air cleaner.