On February 6, 1996, at 1506 hours Pacific standard time, a Cessna 177, N2386Y, crashed about 1/8 mile west of Corona Airport, Corona, California, shortly after departing runway 25. The pilot was beginning a visual flight rules sales demonstration flight. The airplane, owned and operated by Corona Aircraft, sustained substantial damage. Neither the certificated commercial pilot-in-command (PIC) occupying the right front seat, the certificated airline transport pilot occupying the left front seat, nor the two passengers seated in the rear seats were injured. Visual meteorological conditions prevailed. The right seat pilot told Safety Board investigators on February 7, 1996, that he was the PIC. He said that the left seat pilot was a prospective buyer and that the left seat pilot initiated the takeoff. He said that since the left seat pilot was an airline captain, he was not reticent to let him fly. During the takeoff, the left seat pilot rotated the airplane slightly beyond midfield and the airplane immediately lifted off. After lift-off, the airplane did not appear to climb and that the airplane's nose attitude began to porpoise. The PIC assumed the controls when it became apparent that the airplane was not climbing properly. The PIC attempted to lower the nose to gain airspeed, but without success. When he realized that the airplane would not clear the trees at the west end boundary, he turned the airplane 20 degrees to the right to land in an open area. He closed the throttle and the airplane "mushed" to the ground. The airplane nosed over after the initial ground impact. The PIC said that the engine sounded normal throughout the accident sequence of events. The second pilot said in the Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1/2, that he told the first pilot that he had not flown a ". . . light airplane for a long time. . . ." The first pilot said that ". . . it's okay, I'll watch you. . . ." The second pilot generally repeated the first pilot's statement concerning the accident sequence of events. Safety Board investigators examined the engine on April 3, 1996, at National Aircraft Salvage, Long Beach, California. Continuity of the engine gear and valve train assembly was established. Thumb compression was noted throughout the engine crankshaft rotation. The valve travel measurements were found within the manufacturer's specification (see the valve travel measurements table herein this report). The PIC did not submit the required Pilot/Operator Aircraft Accident Report. The PIC's flight time listed on page 3 of this report was obtained from the FAA. The insurer's provided the Safety Board with a copy of the airframe and engine logbooks. Examination of the logbooks revealed that Berlin Avionics, Santa Monica, California, removed and replaced some avionic equipment on August 18, 1995. Berlin Avionics updated the weight and balance data at the conclusion of the installation. Safety Board investigators used the updated weight and balance data and the occupants actual weights to determine the airplane's takeoff weight. The PIC and the second pilot said that the fuel tanks and engine oil sump were filled to capacity before departing on the accident flight. Calculation of the data showed that the airplane's takeoff weight exceeded the maximum allowable gross weight by 154.8 pounds; the center of gravity, however, was within the specified range for the maximum allowable gross weight. A Cessna Aircraft Company engineer reported that the performance data in the airplane's pilot operating handbook was based on the maximum gross weight. He said that the data could not be interpolated for any weight exceeding the maximum allowable gross weight. He said that there is no climb performance data available for the airplane's takeoff weight.