What was found
(CAN) UNDISTINGUISHABLE ODOR OF SOMETHING BURNING, FOLLOWED BY STIFF CARB HEAT CABLE AND ENGINE RUNNING ROUGH WITH CARB HEAT APPLICATION. THE RT EXHAUST STACK HAD CRACKED, HIDDEN BY THE CARBURETOR HEAT SHROUD. DURING FLIGHT, THE HEAT FROM THE EXHAUST BEING EXPELLED FROM THE CRACKED STACK, MELTED THE TOP OF THE CARB HEAT SHROUD (APPROXIMATELY .5000 INCH WIDE AND 4 INCHES LONG). THE EXHAUST ESCAPING FROM THE CARB HEAT SHROUD BLISTERED THE PAINT ON THE FIREWALL, MELTED THE CARB HEAT CABLE GROMMET LOCATED ON THE FIREWALL AND RENDERED THE CARB HEAT CABLE INOPERATIVE IN THE CLOSED POSITION.