The #6 Acura ARX-05 of reigning IMSA champions Montoya and Dane Cameron lapped the 2.358-mile road course in 1min13.057sec to beat the #31 Cadillac by 0.236sec, while Ricky Taylor was just 0.009sec further back in the second Acura.
A late improvement from Harry Tincknell saw him beat Mazda teammate Oliver Jarvis by 0.02sec to land P4, albeit over half a second off the lead Acura.
Meanwhile the two JDC-Miller Motorsports Cadillacs sandwiched the similar car of championship leader Renger van der Zande in the Wayne Taylor Racing entry.
In GT Le Mans, which comprises just four cars following Porsche’s withdrawal, Antonio Garcia was 0.3sec faster than Corvette Racing teammate Tommy Milner. The two BMW M8s were 0.84 and 1.28sec were off the pace.
In fact, Bruno Spengler’s M8 was less than 1sec faster than the Turner Motorsports BMW M6 of Bill Auberlen which topped GT Daytona.
Behind Auberlen by a mere 0.056sec was Jack Hawksworth in the faster of the two AIM Vasser Sullivan Lexus RC Fs, with Alvaro Parente third in the Meyer Shank Racing Acura ahead of Pat Long’s Wright Motorsports Porsche 911 GT3R and Lawson Aschenbach in the Riley Motorsports Mercedes AMG GT3.
The #30 Audi R8 of Hardpoint Racing, driven by Rob Ferriol and Spencer Pumpelly, did not take part in the session due to a technical problem.
Tomorrow’s practice session begins at 10.55am local (Eastern) time, with qualifying not being held until Sunday (raceday) morning.