In a first air flow circuit filtered ram air cooperating with an aspirator draws crankcase vapors from the crankcase of an internal combustion engine. Heavy particulate matter in the crankcase vapor is heated and further vaporized by a heat exchanger cooperating with an exhaust manifold of the engine. A second aspirator draws the vaporized particulate matter back into the original vapor steam of the first air flow circuit. The crankcase vapors mixed with the incoming ram air are then directed into the interior cavity of the carburetor air filter. In a second air flow circuit filtered ram air is directed into the crankcase and carburetor air filter cavity and in a third air flow circuit filtered air is drawn through a variable annular orifice and metered in accord with intake manifold pressure and directed into the engine air intake system below the carburetor throttle plate.