Baylor survived to battle the Mountaineers in overtime when West Virginia's Jabarie Hinds missed the front end of a 1-and-1 foul shot opportunity with 33 seconds left in regulation and the Bears' Pierre Jackson hit a 3-pointer 10 seconds later.
Acy's overtime dunk gave the Bears an 83-78 lead and Hinds hit a 3-pointer with 1:35 left to cut the deficit to two. Neither team scored the rest of the way and Hinds missed a jumper at the buzzer that would have brought about a second overtime.
Baylor improved to 12-0 and stayed among the six teams in the country with perfect records.
Jackson led the Bears with 23 points, Brady Heslip added 19 and Acy had 15. The Mountaineers (9-3) were led by 28 points from Kevin Jones.
West Virginia grabbed a 13-point lead in the first half, but the Bears closed the opening period on a 27-7 run that gave them a 40-33 advantage at the break.