As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE PILOT NOTICED A HIGHER THAN NORMAL MANIFOLD PRESSURE AND DECIDED TO RETURN TO BASE TO INVESTIGATE. FURTHER EXAMINATION REVEALED A LARGE AMOUNT OF ENGINE OIL HAD LEAKED FROM A BENT PUSH ROD TUBE, DUE TO A SEIZED EXHAUST VALVE FOUND IN THE CYLINDER. DAMAGE WAS FOUND ON THE VALVE, PISTON, PUSH ROD AND PUSH ROD TUBE. ENGINE WAS REMOVED AND SENT TO ENGINE SHOP FOR REPAIR.