Reed type Engine Breather Valve (PCV)

Reed type Positive crankcase ventilation Valve. Valve hooks to engine top breather vent and allows expelled air out but reed prevents air re-entering quickly so a very small vacuum is created in the crankcase. A small power increase has been noted during dyno tests (most noteable on pre 77 engines) and the crankcase vacuum helps prevent crankcase pressure from pushing oil past oil seals and case joints.