CHESTNUT MOUNTAIN, Ga. (AP) _ Brian Ongais, son of Indy car driver Danny Ongais, won the Formula Ford national championship Saturday in the narrowest victory in the second day of the Sports Car Club of America's Valvoline Runoffs at Road Atlanta.

Ongais, of Long Beach, Calif., led only the final quarter-mile of the 18 lap, 45-mile Formula Ford race, beating Dave Weitzenhof by three-tenths of a second. Weitzenhof, who led for most of the race, surrendered the lead to Chris Fahan with four laps remaining. On the final lap, Weitzenhof repassed Fahan but Ongais dove inside of Weitzenhof entering the final turn and held on for the victory.

Duane Davis won his third and fourth national championships as he drove the same Renault LeCar to victory in both the GT-4 and GT-5 classes. The victory was Davis' third consecutive GT-5 championship and his first in GT-4.

In the first race of the day, Pepe Pombo led from flag to flag to win the Showroom Stock A class in his Nissan 300ZX.

James Knerr drove his MG Midget to the largest victory of the day as he crossed the finish line 12 seconds ahead of Jeff Lane to claim the national championship in the F Production class.

Luis Sanchez drove his Corvette to an easy victory in the Showroom Stock GT class.

Louis Rettenmeier claimed his third consecutive Formula Continental championship as he drove his Ralt RT-5 to victory at an average speed of 107.17 miles-per-hour in the fastest race of the day.

Bobby J. Studdard drove his Datsun 2000 to the E Production class championship by a 4.5-second margin over Dave McDowell in the final race of the day. Racing continues on Sunday with the final seven national championship races.