20230521007819A

Aircraft departed kjwn 5/21/2023 at approximately 1834Z on a north heading then turning east/southeast to go around nashville/bna airspace. The pilot in command stated aircraft began losing power during flight from kjwn to TN20 approximately 20 to 25 minutes into the flight during cruise and the aircraft started running rough. Pilot stated that almost immediately the aircraft started shaking. The pilot set engine controls to "full rich" and "full power" but continued to lose power while running rough. Pilot noted a lose of altitude and turned on the electric fuel pump and switched fuel tanks. The pilot then switched the mags checking both and tried the carb heat. None of those improved the performance of the engine. The pilot checked for nearest airfield, which was approximaetly 17 miles southeast of current position. Knowing they could not make that airfield the visual search for a best landing location began. Several lage fields were noted nearby. The pilot made a disctress call and informed the tower of the power loss. The tower told them of the airfield 17 miles away to which the pilot replied they would not be able to make that and informed them of the field they had chosen to land. The pilot landed in a farmers field of wheat. Coming to a complete stop in approximateley 130 feet. The nose gear collaped allowing the propeller to make contact with the ground. This caused the aircraft to lift the tail from the ground and rotate clockwise approximately 135 derees before coming to rest on the ground again. Aircraft was found to have 40 plus gallons of fuel onboard, that appeared and smelled like avgas. Inspection of the engine that was accessable, found spark plug leads and sparkplugs to have no freedom of movement by hand. The visual inspection of the engine found all fluid carrying lines to appear fairly new and clean. No signs of leakes were noted. No signs of damage or leakage from any cylinders, intake tubes or what exhaust was visable. Moving the propeller by had for approximately 20 to 30 degrees, internal movement could be heard. Visual external inspection of the magnetos noted no issue and neither magneto could be moved by hand. A visual inspection of the forward and aft mufflers with a borescope found the forward muffler to be saturated with dark engine oild and the aft muffler had no abnormal coatings or signs. The top spark plugs for all cylinders were removed. The spark plugs reflected what was noted from the exhaust mufler inspection, cylinders #1 & #2 were blak and #3 &#4 were noted to be in the condition of correct firing and conditions. Borescope inspection of the #1 cylinder found signs of corrosion pitting and cylinder wear, but valves were noted to be in good condition. Borescope inspection of the #2 cylinder found that the exhaust valve had let go and fallen into the cylinder as numerous signs of the valve impacting the top of the piston in multiple locations were found. All sparkplugs were reinstalled snug, but not torqued, and ignition leads were reinstalled by hand only.