Pilot of homebuilt aircraft reports failure of the fuel selector in the off position. Reporter was able to land successfully on an Interstate highway and make repairs; the aircraft was then flown back to home base.

Narrative

After about 90 minutes of local flying; I tried to switch fuel tanks and the selector failed with the valve in the 'Off' position. I was about 2000 feet at the time over the river and about 20 miles from my home base. The choice for landing was the river; muddy fields or the Interstate. I chose the Interstate as the wind was right down it and there was very little traffic. I landed in the northbound lanes with the traffic. My approach speed was just under traffic flow and I landed without incident. There was no damage to the plane; or cars on the ground and I was not injured. I borrowed a pair of needle nose pliers and was able to manually turn the fuel valve to one of the tanks; I could hear the fuel flow into the header tank and I had good flow at the gascolator. The state police stopped traffic and I proceeded to take off and fly back to home base and land. The plane is a homebuilt replica of a Stinson that I just finished and am in the process of testing it and flying off the hours. I was within my 50 mile radius and over a non-populated area when the trouble occurred.