The pilot reported that during the flight to his return airport, his cruise altitudes had varied from 4,000 ft to 8,000 ft mean sea level (msl) due to mountainous terrain. About an hour into the flight, he switched to the left reserve fuel tank, when the engine began to sputter. Despite switching back to the right fuel tank, the engine lost all power. The pilot initiated a forced landing to an open field and during the landing, the airplane impacted a covered dirt berm, substantially damaging the forward fuselage and left wing. The pilot reported that 2 days prior to the accident, he had topped the airplane off with fuel, which totaled 110 gallons at his home airport. He then flew 2 hours to another airport, with a cruise altitude that ranged between 4,000 to 8,000 ft msl due to mountainous terrain. On the day of the accident, the pilot conducted a preflight inspection on the airplane, which included a visual only inspection of the fuel level in the fuel tanks, which he estimated was about 65 gallons, or enough fuel for the return flight to his home airport. Post accident examination of the airplane revealed that, the airplane came to rest upright in a level attitude, and the fuel selector lever was observed in the left tank position and would not move. Damage to the fuel line near the center fuselage, was consistent with impact, and the fuel line was not breached. Recovery personnel reported that there was no fuel was recovered from the left fuel tank, and about 1/2 gallon of fuel was recovered from the right fuel tank. However, it was later reported after the airplane had been recovered, the left tank had about 5 to 10 gallons of fuel. The airplane was equipped with two 55-gallon fuel tanks, of which 51 gallons were considered usable. The selector lever had four positions, “LEFT,” “RIGHT,” “RESERVE,” and “OFF.” The left fuel tank was designed to have fuel drawn from two different locations as the fuel tank was equipped with a standpipe. The left position drew fuel from the upper portion of the fuel tank with 33.5 gallons of usable fuel, while the reserve position drew fuel from the bottom of the left fuel tank, with 17.5 gallons of useable fuel. A subsequent examination of the accident airplane reveled that the left wing fuel tank was not breached. The fuel selector valve and lever, wobble pump, and engine driven fuel pump were removed, with no visible damage to any of the components. Once removed, the fuel selector handle was free to rotate to all the positions on the fuel selector valve. A functional test of the fuel system revealed that when the fuel selector lever was in the “RESERVE” position, with the other ports capped off, interrupted fuel was observed flowing through a clear tube attached to the outlet. When the other fuel ports were uncapped, air bubbles were seen flowing in the fuel outlet line. The same functional test was performed at the other inlet positions for the fuel selector valve with less air bubbles observed. For flight planning purposes, the pilot estimated 30 gal an hour (gph). According to the Pilot’s Operating Instructions for airplane, the fuel supply is “normally sufficient for 3.9 hours cruising.” However, at “High Power,” the fuel consumption ranges from 30 gph to 56 gph depending on what RPM and manifold pressure settings were used. The total amount of fuel onboard the airplane before the accident flight could not be determined. Given the lack of fuel found in the right tank after the accident and the limited fuel in the left tank, it is likely that the pilot failed to ensure that the fuel selector lever was placed in the “RESERVE” detent, and mistakenly selected the ”LEFT” position, which resulted in a total loss of engine power due of fuel starvation.