As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HEAD SEPARATED AT DOME. SEPARATION STARTED AT 4 O'CLOCK POSITION AND 11 O'CLOCK AND PROPAGATED UNTIL TOTAL FAILURE. EXHAUST AND OIL DRAIN HELD CYLINDER ON ENGINE, 900 SMOH. SUBMITTER STATED BETTER DYE-PEN INSPECTION AT OVERHAUL WITH PARTICULAR ATTENTION TO EXHAUST PORT. RETIRE CYLINDER AFTER SECOND RUN. CYLINDER WAS OVER 20 YEARS OLD. AGE MAY HAVE BEEN A FACTOR.