As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER REMOVAL OF CYLINDER NR 4 DUE TO A LEAKING EXHAUST VALVE, A 4 INCH CRACK WAS FOUND STARTING AT THE NR 2 MAIN JOURNAL. THIS CRACK STARTED AT THE BEARING SURFACE AND PROGRESSED TO THE INSIDE OF THE CASE BETWEEN CYLINDERS NR 2 AND 4. NO EVIDENCE OF A CRACK WAS FOUND ON THE OUTSIDE OF THE CASE. SUBMITTER STATED THIS IS THE 3RD CRACK FOUND IN THIS AREA ON 3 DIFFERENT ENGINES.