BE58 PLT HAD SMOKE IN THE COCKPIT IN ZHU CLASS E AIRSPACE.

Narrative

THE FLT WAS IN AND OUT OF NUMEROUS RAIN SHOWERS AND TEMP AT 14000 FT WAS ZERO TO -2 DEGS C. I WAS TRAINED TO TURN ON ANTI-ICE FROM BELOW 10 DEGS C. THE FLOWING ITEMS WERE ON: ALL RADIOS; NAVS; RADAR; STRIKE FINDER; ARGUS; ADF; XPONDER; RNAV; GPS; INTERCOM. IN ADDITION; THE FOLLOWING ITEMS WERE ON: STALL WARNING HEAT; FUEL VENT HEAT; PITOT HEAT AND WHEN IN RAIN I WOULD PUT THE PROP HEAT ON. AT APPROX 1.45 MINS INTO MY FLT; I WAS AT 14000 FT WITH DISCRETION TO 7000 FT AND APPROX 65 MI TO MY DEST; I SMELLED SOMETHING. I IMMEDIATELY LOOKED DOWN AND SAW SMOKE COMING INTO THE CABIN FROM UNDER MY YOKE BELOW MY SWITCHES. I IMMEDIATELY TOLD ATC AND WAS CLRED TO 4000 FT. I BEGAN AN EMER DSCNT; DUMPED THE CABIN PRESSURE AND TURNED ALL THE SWITCHES AND AVIONICS OFF EXCEPT THE RADIO AND GPS. SMOKE CONTINUED FOR APPROX 30 SECONDS AND I REMOVED THE FIRE EXTINGUISHER AND OPENED MY SIDE WINDOW AS I LEVELED AT 4000 FT. I REQUESTED THE CLOSEST ARPT AND THEY VECTORED ME TO KERRVILLE AND CLRED ME FOR THE APCH. THE SMOKE HAD STOPPED AT THIS TIME AND BROKE OUT INTO VFR APPROX 5 MI TO THE ARPT AND LANDED IMMEDIATELY. UPON LNDG; I SHUT EVERYTHING DOWN AND WENT TO THE FBO AND CALLED TO CANCEL AND LET ZHU KNOW I WAS ON THE GND WITHOUT INCIDENT.