What was found
(CAN) PILOT REPORTED LOW OIL PRESSURE READING 10 MINUTES PRIOR TO LANDING. VISUAL INSPECTION OF ENGINE EXTERIOR & OIL LEVEL CHECK CARRIED OUT BY PILOT. 3 LITERS OF OIL ADDED. AIRCRAFT TEST FLOWN, TAKEOFF NORMAL, RUN UP WAS NORMAL, AT CRUISE POWER OIL PRESSURE STARTED DECREASING 5 MINUTES AFTER CRUISE POWER SET. AIRCRAFT RETURNED FOR LANDING. MAINTENANCE FLOWN DOWN TO INSPECT ENGINE. METAL FOUND IN OIL, OIL FILTER AND SCREEN. ENGINE TAKEN OFF LT SIDE OF AIRPLANE. AFTER ENGINE OVERHAUL, FOUND THAT THE ENGINE CAMSHAFT LOBS WERE WEARING OUT CAUSING METAL PARTICLES IN THE ENGINE OIL.