What was found
(CAN) THE AIRCRAFT WAS CRUISING AT 4500 ASL WHEN THE ENGINE BEGAN RUNNING ROUGH, SOME SMOKE WAS SEEN, THE ENGINE WAS SHUT DOWN AND A SUCCESSFUL FORCED LANDING WAS CARRIED OUT ON A LAKE 26.5 NM SOUTH OF PUVIRNITUQ, QUEBEC. INVESTIGATION INTO THE CAUSE FOUND THAT THE VALVE HEAD OF NR 2 CYLINDER EXHAUST HAD SEPARATED AND BEAT ABOUT THE PISTON AND CYLINDER HEAD UNTIL THE CYLINDER HEAD FINALLY CRACKED OPEN. NR 2 CYLINDER AND PISTON ASSEMBLY WERE REPLACED. ENGINE WAS GROUND RUN AND FOUND SERVICEABLE. (X)