At about 1537 Eastern time, the airplane was substantially damaged during a forced landing. Visual conditions prevailed. The private pilot and one passenger were not injured. During descent from cruise, the engine began vibrating/shaking. The pilot executed emergency procedures, advised ATC and continued toward the nearest airport. Unable to make the airport, the pilot secured the engine and configured the airplane for an off-airport landing in an open field when it collided with the tops of pine trees. Approximately three to four seconds later, the airplane was on the ground with a collapsed nose landing gear. Examination revealed the exhaust valve of the No. 3 cylinder was missing and the cylinders piston exhibited heavy impact damage.
