What was found
(CAN) AFTER TAKEOFF THE PILOT NOTICED A DROP IN MANIFOLD AND OIL PRESSURES ON #2 ENGINE. THE ENGINE WAS SHUTDOWN AND THE AIRCRAFT RETURNED TO BASE. POST FLIGHT INSPECITON FOUND THE #2 ENGINE COWLING SATURATED WITH ENGINE OIL. FURTHER INVESTIGATION FOUND THE VACUUM PUMP GASKET WAS LEAKING. THE PUMP WAS NEWLY INSTALLED AND THE FAULTY GASKET CAME WITH THE PUMP. A NEW LYCOMING VACUUM PUMP GASKET P/N 8313 WAS INSTALLED AND THE ENGINE GROUND RUN SERVICEABLE.