Youngsters ages 8 to 17 can sign up for the South Placer Soap Box Derby to be held Oct. 22 to 24 at 2000 Omega Drive in Lincoln. Entry fee is $55; rent cars for as low as $50 for the weekend. For more information, contact Ernie Farrington at 872-9612. Race cars are powered by gravity and are timed as they roll down either a dedicated track or a temporary street circuit. The goals of the Soap Box Derby program have not changed since it began in 1934: to teach youngsters some of the basic skills of workmanship, the spirit of competition and the perseverance to continue a project once it has begun.