On September 19, 2007, about 1615 eastern daylight time, a Beech V35B (Bonanza), N9271Q, piloted by a private pilot, was substantially damaged during a forced landing following a loss of engine power shortly after takeoff from runway 27 (3,500 feet by 75 feet, asphalt) at the Portage County Airport, Ravenna, Ohio. Visual meteorological conditions prevailed at the time of the accident. The instructional flight was operating under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. The pilot and his flight instructor were not injured. The local area flight was originating at the time of the accident. The accident occurred during the first flight after all six engine cylinders had been replaced. Three days prior to the accident, the pilot performed an engine run-up to verify proper engine operation and to establish if any fluid leaks were present. No anomalies were encountered during the engine run-up and no fluid leaks were noted after engine shutdown. On the day of the accident, the airplane had 65 gallons of fuel distributed evenly between the two fuel tanks and no fuel contamination was noted during a preflight inspection. The pilot reported that during taxi he completed all checklist items, including verifying proper oil pressure and magneto operation. The fuel selector was selected on the left fuel tank and the auxiliary fuel pump was in the "off" position. He applied full engine power for takeoff and observed proper oil pressure prior to liftoff. The airplane became airborne between 75 and 80 knots and the landing gear was retracted after crossing the departure threshold. Engine rpm and manifold pressure was then reduced to 2,500 rpm and 25 inches-of-mercury, respectively. The engine lost power 500 - 600 feet above ground level during initial climb. An immediate forced landing was made to a cornfield southwest of the airport. During the forced landing, the stall warning horn reportedly sounded shortly prior to impacting a tree. The airplane then impacted the cornfield nose down and came to an abrupt stop. The engine, a Teledyne Continental Motors IO-520-BA12B, serial number 280870-R, was sent to the manufacturer for an operational test run under the supervision of the NTSB investigator-in-charge. The engine was installed in a test cell and outfitted with a test club propeller. The engine started on the first attempt and idled without excessive fluctuations in engine rpm. The engine speed was increased incrementally to 2,700 rpm over a period of 30 minutes. The engine ran at each incremental power setting for a period of 5 minutes without anomaly. The engine throttle was cycled several times between idle and maximum power settings in quick succession. The engine did not experience any hesitation, stumbling, or interruption in engine operation during the engine test run. The engine demonstrated the ability to produce rated horsepower.