A BE35 AT 3500 FT NOTED DROP IN OIL PRESSURE. ADVISED ATC AND ADVISED TO DSND TO 2000 FT. ON DSCNT LOST DIRECTIONAL GYRO AND AUTOPLT. ADVISED TO DSND TO 600 FT AND BROKE OUT OF CLOUDS AND PROCEEDED TO ARPT.

Narrative

IN THE MORNING I RECEIVED AN FSS BRIEFING AND ALSO LOOKED AT NOAA WX ON-LINE. THE TRIP ORIGINATED AT ZZZ; US; WITH A STOP AT ZZZ1; US; ON AN IFR FLT PLAN. ON THIS LEG I QUICKLY PICKED UP ICE WHEN BRIEFLY ENTERING THE CLOUDS. AFTER DEPARTING ZZZ1 I ELECTED NOT TO PICK UP MY IFR FLT PLAN AND STAY UNDER THE CLOUD CEILING OF 3500 FT. FORECAST CEILINGS IN THE ZZZ2 AREA WERE 1300-2500 FT. I COULD NOT PICK UP ZZZ2 ATIS OR ZZZ2 AWOS UNTIL ABOUT 20 MI FROM ZZZ VOR. AT THIS TIME I HEARD OF CEILINGS OF 500-600 FT. I CLBED TO 3500 FT AND CALLED ZZZ2 APCH AND REQUESTED THE ILS. AT THIS TIME I BECAME AWARE OF A DROP IN OIL PRESSURE. ZZZ APCH GAVE ME AN INITIAL HDG OF 170 DEGS AND DSND TO 2000 FT. ON ENTERING THE CLOUDS THE DIRECTIONAL GYRO SEEM TO FIRST SWING OFF HDG AND MY AUTOPLT WOULD NOT HOLD THE HDG. I RECYCLED MY AUTOPLT; BUT IT WOULD STILL NOT HOLD THE HDG. WHILE TRYING TO SET MY DIRECTIONAL GYRO TO THE COMPASS I FELL BELOW 2000 FT. AFTER THE CTLR RADIOED THAT I HAD A POSSIBLE DIRECTIONAL GYRO PROB I STARTED TO RELY ON MY COMPASS AND GPS TO NAV. ATC INSTRUCTED ME TO GET LOWER TILL I BROKE OUT OF THE CLOUDS. I THEN WAS INSTRUCTED TO PROCEED TO ZZZ4 ARPT. THE NEXT MORNING I WENT BACK TO ZZZ4 ARPT TO POSSIBLY BRING MY PLANE TO ITS HOME ARPT. UPON CRANKING THE ENG I HAD NO OIL PRESSURE INDICATED AND NO DROP WHEN FEATHERING THE PROP. MY ACFT REMAINS AT ZZZ4. I HAVE ALREADY TOLD MY MECH THAT I'LL WANT ANOTHER DIRECTIONAL GYRO. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE AIRPLANE HAD MAJOR ENG WORK AND WAS OPERATED FOR 11 HRS UNTIL THE DROP AND LOSS OF OIL PRESSURE INCIDENT. HAD A TECHNICIAN CHK THE ENG OVER AND IT WAS DISCOVERED THE OIL PRESSURE RELIEF VALVE WAS JAMMED OPEN BY BITS OF BRASS SAFETY WIRE. CLEANED EVERYTHING AND THE ENG OPERATED NORMALLY. A NEW DIRECTIONAL GYRO CORRECTED THE INSTRUMENTATION AND AUTOPLT PROB.