Harper and the Tigers came out throwing to take a 21-0 lead before the game was 17 minutes old -- and brought their coach, Tommy, his third straight win over father Bobby's Seminoles.
Florida State rallied from 24-3 down in the second half of the season opener for both teams. When Drew Weatherford hit Richard Goodman for a 15-yard TD pass with 11:40 left, the Seminoles trailed by 6.
Weatherford and the Seminoles got the ball back three more times after that, but could not score.
"It looked like stage fright. We were running a new offense but I thought we grasped it better than that. We were bad," Bobby Bowden said.
Clemson fans rushed the field and the collapsible goal posts came down after Weatherford's final pass fell to the ground. But officials chose to review the play, moving orange-clad fans out of the way.
Finally, they were told the play stood and the game was indeed over.
Florida State had a rough first half, managing only one first down and 62 yards. The Seminoles, however, found their rhythm in the second half.
Antone Smith had a 49-yard run to Clemson's 1, then followed with the score that drew them to 24-11. Goodman's TD catch tightened things up even more.
But Weatherford and the Seminoles couldn't sustain the rally.
They got to Clemson's 31 with 3 minutes left. But Florida State's junior quarterback threw three incompletions and was taken down from behind by defensive lineman Philip Merling.
Harper was 14-of-24 for 160 yards and no interceptions. Davis gained 102 yards on 18 carries.
The victory closed Tommy within a win of his father after the ninth meeting of college football's best known family feud.
Bobby's Seminoles won the first four games in the series by a combined score of 160-79. Tommy won four of the past five, including the last three at Death Valley.
Bobby Bowden said he can't be certain the Seminoles will rebound from their fifth loss in their last eight games. "You never know. The season's too young," he said.
Clemson got things going with a reverse to Jacoby Ford that went for 34 yards to Florida State's 23. Three plays later, Harper found Linthicum for an 11-yard touchdown pass.
The Tigers were at it again moments later when linebacker Nick Watkins recovered Preston Parker's fumble.
Davis, who gained 1,187 yards a year ago, showed off his power on the next play, breaking two tackles and cutting hard left near the goal line for his 29-yard touchdown and a 14-0 lead.
Two series later, Harper hooked up with Kelly for a 41-yard touchdown pass.