Tackle Mike Russo ran 21 yards with an intercepted pass early in the fourth period to cap a two-touchdown rally that gave unbeaten, third-ranked Penn State a 16-12 victory over Boston College yesterday at State College, Pa.

The Nittany Lions trailed, 12-3, in the third period before D.J. Dozier keyed an eight-play, 74-yard drive with a 42-yard run for a first down at the Boston College 12. Three plays later quarterback John Shaffer dove across from the one to make it 12-10 with 1:40 left in the third period.

John Bruno punted 71 yards into the Boston College end zone and the Eagles (3-7) took over at their 20. On third down, quarterback Shawn Halloran's pass was tipped by defensive tackle Tim Johnson into the hands of Russo, who scored with 13:46 left in the game. A pass for a two-point conversion fell incomplete.

"This has been one of the few times our offense has turned the ball over with bad field position," Penn State Coach Joe Paterno said of his 8-0 team's two fumbles and one interception. " . . . But we hung in there tough . . . "