On July 4, 2005, at 1430 eastern daylight time, an Aeronca C3, N14532, registered to and operated by a private owner, collided with trees and subsequently the ground five miles south of Summerville Airport, Summerville, South Carolina. The flight was operated under provisions of Title 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident and a flight plan was not filed. The airplane sustained substantial damage, the private pilot and passenger received serious injuries. The flight originated from Summerville Airport, Summerville, South Carolina, on July 4, 2005 at approximately 1400. According to the pilot, he and his wife were taking their restored 1935 Aeronca C-3 for a pleasure flight. Approximately 25 minutes into the flight the pilot reported a smooth engine RPM drop from 2400 to 1000. The pilot selected "Jedburg Airport (old Summerville airport)" for an emergency landing. The pilot entered the traffic pattern at 500 feet, but another airplane was on the runway. The pilot began to make a 360 degree turn for spacing, but decide that he did not have enough altitude to complete the turn. The pilot elected to make an off airport landing onto the canopy of a near by stand of trees. Before hitting the trees the pilot stated that he intentionally stalled the airplane. The post-accident examination of the airplane revealed left and right wing circular crush damage. Post-accident examination of the engine revealed that the intake valve clearance was out of adjustment. The clearance between the rocker arm and valve stem exhibited excess clearance. Further investigation revealed that the intake valve would not open because the mechanical pushrod lifter was out of adjustment. The intake lifter adjustment jam nut was loose and the lifter adjustment had bottom out. The intake lifter would not allow proper travel of the pushrod and rocker arm. The rocker arm could not compress/open the intake valve. A review of the airplane maintenance log revealed that the valve assembly was last adjusted on November 24, 2004.