The normal breather between the cam tower and the intake manifold has a shielded orifice just 2.5 mm in diameter to limit flow between the engine crankcase gases and the intake tract below the throttle plate. This functions mainly during idle and low-power conditions.

The hose from the valve cover to the air cleaner exchanges air/gases between the crankcase and the air cleaner intake, above the throttle plate. This pulls fresh air into the crankcase when the breathing requirements exceed the flow rate of the orifice.

With the vacuum pump or check valve compromised there is a direct large-diameter path for crankcase gases to pass directly into the intake tract below the throttle plate--a torn diaphragm will allow copious amounts of oil mist to be sucked into the intake manifold and burned.

I would suspect you have an intake-side problem or that the new carb setup has disturbed normal engine breathing somehow. Oil leaks are symptomatic of high crankcase pressure and poor engine breathing.


Tim Kraakevik
kraakevik@voyager.net
630 474-9164