A few years ago, on a ferry flight to collect another plane, the engine on the Cub I was flying P2 decided to drop a valve into a piston, 5 miles from our destination. On a delightful October afternoon my pal, having just finished his instructor training, did a pefect dead stick landing into a field of recently sown winter wheat, after we both automatically checked fuel and carb heat. We discovered that the Cub's track exactly matched the tractor tracks so we could mitgate any damage. After a hooligan ride in a Police VR6 to the airfield, we returned to hide the Cub and inspect the damage. The valve was visible across the spark plug hole!!
We collected the plane I was due to fly back, 300' up, smoke was seen creeping out of the cowling, a quick U turn and clearance to an opposite direction runway saw us being chased along the taxiway by an extremely large fire engine. Engine runs were done, but no problem could be repeated. Now getting towards dark, we decided to get the train back to base. Have you ever been on an HST when they really hit the brakes for a station? -you get a heavy smell of burning......Other passengers looked on as two grown men collapsed into hysterics....