On October 5, 2001, about 1315 eastern daylight time, a Cessna 170, N4180V, registered to Vega Aero Services, Inc., experienced a loss of power during the initial climb after takeoff and collided with terrain during a forced landing near Bennettsville, South Carolina. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 personal flight. The airplane was substantially damaged and the commercial-rated pilot and one passenger were not injured. The flight originated about 2 minutes earlier. The airplane was flown a total of approximately 2 hours 25 minutes on two separate flights since the fuel tanks were filled. The first flight was approximately 2 hours duration taking place 1 day before the accident. The second flight lasted approximately 25 minutes and took place earlier on the accident date departing with nearly full fuel in the left fuel tank and approximately1 hour of fuel remaining in the right fuel tank. The pilot stated that after takeoff on the accident flight with the fuel selector positioned to the "both" position, the engine quit when the flight was approximately 200 feet above ground level. The pilot maneuvered the airplane for a forced landing in a field and while in a foward slip; the right main landing gear collided with a ditch. The right wing then contacted the ditch and the airplane came to rest. The pilot and passenger exited the airplane out the right door. Postaccident examination of the airplane by the pilot/owner who is also an airframe and powerplant mechanic revealed that the vent line which connects to both fuel tanks was blocked near the left wing root area. Additionally, the fuel supply line between the fuel selector valve and the fuel strainer was found to be kinked and foreign matter was found inside the kinked line. The owner/pilot reported that the damage to the line was not the result of the forced landing and subsequent damage to the airplane.