As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) #5 CONNECTING ROD FAILED AND FRACTURED R/H HALF OF CRANKCASE AND CAMSHAFT BROKE. SUBMITTER SUSPECTS THAT ENGINE HAD BEEN OVERPRIMED PREVIOUSLY AND HAD CAUSED A HYDRAULIC LOCK ON THE CYLINDER BENDING THE CONNECTING ROD CAUSING IT TO FAIL SOMETIME LATER. #5 CYLINDER IS LOWEST POINT ON INBOARD SIDE OF THE LEFT HAND ENGINE. THERE IS ALSO NO INTAKE MANIFOLD DRAIN PROVIDED AT THIS LOCATION. THIS IS A FAULT WITH CESSNA 300 AND 400 SERIES ENGINES.