There is a difference of opinion going around the marina in which I moor about the air filter housing on the 45hp Barrus Shire. There are two openings on the cylindriacl housing (one at the bottom of the removable cover and one at the back closest to the manifold) that would appear to allow air flow to the "dusty" side of the filter.
However, these ports are fitted with rubber flapper valves that close on suction from within the housing. ie. When the engine is running. Now some people are taking one if not both of these valves out claiming that they are starving air-flow to their engine but surely these are fitted for a reason and working on a '"if it ain't broke, dont fix it" principle should they be leaving well alone????
I pose the question then:
What are these valves? and are they required????