What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
At cruise flight, both pilots felt a slight “thud” and smelled a faint chemical smell. With no abnormalities noted, the engine started running very rough and smoke started to enter the aircraft. Pilots secured the engine power, declared an emergency, and continued descent to kuts. After landing smoke observed coming from the engine compartment, fire extinguisher was discharged into the engine compartment. Pilots observed the spinner was missing from the propellor. The nose tire was observed to be flat. After removing engine cowling, a hole was observed on the top of the engine block at the rear two cylinders with a cylinder connecting rod resting on top of the engine.
As the FAA filed it
AT CRUISE FLIGHT, BOTH PILOTS FELT A SLIGHT “THUD” AND SMELLED A FAINT CHEMICAL SMELL. WITH NO ABNORMALITIES NOTED, THE ENGINE STARTED RUNNING VERY ROUGH AND SMOKE STARTED TO ENTER THE AIRCRAFT. PILOTS SECURED THE ENGINE POWER, DECLARED AN EMERGENCY, AND CONTINUED DESCENT TO KUTS. AFTER LANDING SMOKE OBSERVED COMING FROM THE ENGINE COMPARTMENT, FIRE EXTINGUISHER WAS DISCHARGED INTO THE ENGINE COMPARTMENT. PILOTS OBSERVED THE SPINNER WAS MISSING FROM THE PROPELLOR. THE NOSE TIRE WAS OBSERVED TO BE FLAT. AFTER REMOVING ENGINE COWLING, A HOLE WAS OBSERVED ON THE TOP OF THE ENGINE BLOCK AT THE REAR TWO CYLINDERS WITH A CYLINDER CONNECTING ROD RESTING ON TOP OF THE ENGINE.