A B36 BONANZA PVT PLT PERFORMS AN OFF ARPT EMER LNDG WHEN HIS ENG FAILS TO PRODUCE ADEQUATE PWR TO ENABLE HIM TO LAND ANYWHERE EXCEPT ON A HARD SURFACED ROAD 5 MI NW OF ADS; TX.

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AFTER A NORMAL RUN-UP; MAGNETO CHK; FULL PWR CHK AND ADEQUATE GND RUN TO PROPERLY WARM THE ENG; I ANNOUNCED MY INTENTIONS ON THE CTAF AND DEPARTED F69 FROM RWY 34. ONCE AIRBORNE; ADDISON TWR WAS CONTACTED. WHEN ATC HAD RADAR CONTACT; A TURN TO THE L (OR W) WAS INITIATED TO RETURN TO F69 AND ORBIT THE ARPT. SUDDENLY; AND WITHOUT ANY ADVANCED WARNING FROM THE GAUGES; THE ENG BEGAN TO SHUDDER. A NOTICEABLE REDUCTION IN PWR WAS DETECTED AND REDUCTION IN OIL PRESSURE. WHEN IT BECAME APPARENT THAT THE ENG WAS NOT MAKING SUFFICIENT PWR TO KEEP THE ACFT AIRBORNE; I BEGAN TO LOOK FOR PLACES TO LAND BECAUSE I COULD NOT MAKE IT TO ANY ARPT FROM MY PRESENT ALT. I WAS HDG S JUST N OF THE BAPTIST CHURCH; A HEAVILY POPULATED AREA. IN AN EFFORT TO AVERT DAMAGE OF PROPERTY ON THE GND; I TURNED BACK TO THE NNW. AT THIS TIME; I SWITCHED TANKS IN AN EFFORT TO RESTORE PWR. THIS HAD NO EFFECT ON THE PWR OUTPUT OF THE ENG. I ATTEMPTED TO ADJUST THE THROTTLE SETTING AND THIS HAD NO EFFECT ON THE PWR OUTPUT OF THE ENG. I CALLED ADDISON TWR AND INFORMED THEM THAT I WAS HAVING ENG PROBS AND I COULD NOT MAINTAIN ALT. I SURVEYED ALL AVAILABLE LNDG AREAS AND ULTIMATELY DECIDED UPON A HARD SURFACE ROAD THAT APPEARED TO BE MY BEST LNDG SITE SINCE NO AUTOMOBILES WERE OBSERVED ON THE ROAD. I ALIGNED WITH THE MIDDLE OF THE ROAD AND AFTER CLRING A HORIZ WIRE; LOWERED THE LNDG GEAR. I MANEUVERED UNDER ANOTHER HORIZ WIRE SUBSEQUENTLY LNDG WITHOUT INCIDENT. I SECURED THE COCKPIT BY TURNING FUEL; MAGNETOS AND MASTER SWITCH OFF AND EXITED THE ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT HIS ENG WAS INSPECTED AFTER THE EVENT. INITIAL INSPECTION REVEALED A FAILURE OF THE PISTON ROD NUT. THE SYS HAS A NEW STYLE NUT HOLDING THE PISTON ROD TO THE CRANK SHAFT. THIS NUT DESIGN/FAILURE ALLOWED THE ROD TO PULL THROUGH THE RETAINING NUT. THE ENG WAS OPERATING ON A REDUCED NUMBER OF CYLINDERS. THERE WERE OTHER CASES OF THIS RPTED TO HIM BY FRIENDS; ONE HAVING 3 RODS LET GO. SOME OF THE CASES WERE WITHIN 5 HRS OF INSTALLATION OF THE REBUILT MOTOR. HIS ENG; WITH NEWLY CHROMED CYLINDERS; HAD 23 HOURS. THE BEECH OWNER'S FORUM; THE MANUFACTURER; FAA AND THE NTSB ALL KNOW ABOUT THE PROB. THE FAA HAS ISSUED AN AIRWORTHINESS DIRECTIVE ABOUT THE CRANKSHAFT/PISTON ROD ATTACHMENT NUT IN QUESTION.