A C182RG IN CLB AT 6000 FT DECLARED AN EMER AND DIVERTED DUE TO STRONG ELECTRICAL BURNING ODOR AND SMOKE IN CABIN. CAUSED BY BROKEN EXHAUST MANIFOLD.

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I WAS CLBING FROM 4000 FT TO 7000 FT WHEN A STRONG SMELL OF ELECTRICAL BURNING OCCURRED AND A WHIFF OF SMOKE APPEARED FROM UNDER PANEL. I DECLARED AN EMER TO DEP CTL AND DSNDED AND RETURNED TO ZZZ. THE SMELL SEEMED TO GET BETTER AND THE SMOKE NO LONGER APPEARED ONCE DIVE WAS INITIATED. THIS PROMPTED THE DECISION TO CONTINUE TO ZZZ RATHER THAN THE CLOSER ARPT. THE CONTINUED FLT AFTER INITIAL DIVE/LNDG WAS UNEVENTFUL. UPON LNDG; THERE WERE 500+ SCORCH MARKS O R SIDE OF COWL. THE PANEL LIGHTS AND GAUGE ILLUMINATION LIGHTS WERE FLASHING ON AND OFF THROUGHOUT THE DSCNT; LNDG AND TAXI. THE GENERATOR'S TEMP MONITOR FOR CYLINDER #1 STOPPED RESPONDING AT SOME POINT DURING DSCNT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAUSE OF THE SMOKE AND ELECTRICAL BURNING ODOR WAS A FAILED EXHAUST MANIFOLD WHICH ALLOWED HOT EXHAUST GAS TO BURN WIRING; BAFFLES AND ENTER THE CABIN HEATER SYS. THE WIRING INCURRED SEVERE DAMAGE AND THE ENG COWLING WAS SCORCHED. A PREFLT DID NOT REVEAL ANY EXHAUST MANIFOLD CRACKS PRIOR TO FLT.