What was found
PILOT REPORTED OIL LEAK ON THE LT ENGINE FOLLOWING A FLIGHT OF APPROXIMATELY 1 HOUR. MAINTENANCE UNCOWLED ENGINE AND DISCOVERED AN EXHAUST STUD FROM THE NR 4 CYLINDER HAD BACKED OUT OF EXHAUST FLANGE. STUD BOUNCED AGAINST THE PUSH ROD HOUSING WEARING A HOLE THROUGH IT APPROX THE SAME SIZE AS THE STUD DIAMETER CAUSING THE OIL LEAK. ENGINE WAS OPERATING NORMALLY WITH THE EXCEPTION OF THE REPORTED OIL LEAK. AN INVESTIGATION REVEALED A CRACK EXTENDING FROM THE EXHAUST PORT TO STUD RETENTION AREA. CRACK RELIEVED TENSION ON THE STUD CAUSING IT TO BECOME DISLODGED. FURTHER INVESTIGATION REVEALED 4 OF 6 CYLINDERS HAD CRACKS IN SAME GENERAL AREA.