On October 13, 1996, at 1235 central daylight time, a Harper W-8 Tailwind, N91323, collided with trees while attempting a forced landing to a private airstrip near MacClenny, Florida. The personal flight operated under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane sustained substantial damage, and the pilot received serious injuries. The flight departed a private airstrip in MacClenny, Florida, at 1230. The pilot reported that he landed at a private airstrip in MacClenny and refueled with seven gallons of automotive fuel. There was no record of the pilot checking the fuel system for contaminates after he refueled the airplane. As the pilot taxied for takeoff, no mechanical problems with the airplane were experienced, but while climbing through 150 feet after takeoff, the pilot experienced a rough engine condition followed by a loss of engine power. He elected to return to the airport for the emergency landing. The airplane collided with trees short of the airport. The examination of the airplane disclosed that the fuel system was refueled with automotive fuel. Further examination disclosed that there was rust and debris in the fuel tank, gasculator, carburetor inlet screen, and carburetor bowl. The examination of the engine failed to disclose a mechanical problem. A review of the aircraft and engine log showed the engine was a surplus military Lycoming-Spencer O-290-G4.