Montoya, driving the No. 42 Chevrolet for Earnhardt Ganassi Racing, shot to the top of the leaderboard with a lap at 185.410 mph with about 10 minutes left in the opening 90-minute session. Kurt Busch was a distant second, more than seven tenths of a second back at 184.347 mph in the No. 78 Furniture Row Racing Chevrolet.
Austin Dillon, winner of Wednesday night's inaugural Mudsummer Classic for the NASCAR Camping World Truck Series at Eldora Speedway's dirt track, was third-best at 183.944. Paul Menard and Kasey Kahne completed the order in a top-five sweep by Chevrolets in preparation for the Crown Royal Presents the Samuel Deeds 400 at the Brickyard (1 p.m. ET, ESPN).
Series points leader Jimmie Johnson -- a Brickyard winner four times, including last year's running -- was 13th-fastest in the opening practice.
The Sprint Cup Series has a final, two-hour practice session scheduled Saturday at 9 a.m. ET. The series will have qualifying Saturday at 2:10 p.m. ET.
FULL SERIES COVERAGE