At about 12:00 eastern time, a Cessna 210L suffered a catastrophic engine failure while in cruise flight near Bluefield. The pilot made a successful forced landing at Mercer County Airport. The pilot was in cruise flight at 8,000 feet when the engine began to vibrate, the propeller oversped and the oil pressure dropped to zero. The pilot then saw flames coming from the engine cowling and the cockpit filled with smoke. The engine showed a three-inch hole in the engine case. The airplane had been operated for about 4 hours since an annual inspection, at which time the Nos. 1 and 2 cylinder and piston assemblies were replaced and all of the intake and exhaust valve lifters were replaced.