Karam, driving the No. 8 Schmidt Peterson with Curb-Agajanian car, posted the fastest lap of the lone practice session on the 1.683-mile, 10-turn MD Anderson Cancer Center Speedway at 1 minute, 09.3931 seconds on his last of 29 laps.
Karam enters the 50-lap Grand Prix of Houston with a two-point lead over Carlos Munoz. Gabby Chaves is four points back and Jack Hawksworth is 11 points arrears. All were within a second of Karam's fast lap with a few seconds remaining in the session.
A 45-minute qualifying session at 8:45 a.m. (ET) will be followed three hours later by the 50-lap race. NBC Sports Network will broadcast the race of the season at 4 p.m. (ET) Oct. 6, following the IZOD IndyCar Series race.