Brad Jones Racing’s Andre Heimgartner is the pace-setter by more than a second after the morning session of the official Supercars test day at Sydney Motorsport Park.

The #8 R&J Batteries Chevrolet Camaro occupies top spot on the timesheet with a 1:29.8268s against it after the opening four-hour session, the first time that all 25 of the initial batch of Gen3 cars have been at a race track together.

In an all-Camaro top three, Erebus Motorsport’s Will Brown sits second on a 1:31.1405s in the #9 Coca-Cola entry, from another BJR driver in Jack Smith, who has set a personal-best 1:31.1607s in the SCT Logistics-backed #4 machine.

Will Davison is first of the Ford contingent with a 1:31.4006s in Dick Johnson Racing’s #17 Shell V-Power Racing Team Mustang.

The picture is somewhat clouded, however, given differences in programmes and tyre banks, with teams having the full slick compound range available to them.

UPDATE: Team owner Brad Jones confirms Heimgartner ran on new super soft tyres during the morning

The track was wet from overnight rain when pit lane opened at 08:30 local time/AEDT, with light falls continuing intermittently over Eastern Creek for the first two hours or so.

Red Bull Ampol Racing’s Shane van Gisbergen wasted little time in moving to the top of the timing screen when drivers began to roll out on wet tyres at the start of the session, holding sway on a 1:42.5942s at the end of the first half-hour in his #97 Camaro.

The 2022 champion improved to a 1:42.4153s late in the first hour and a 1:42.3966s early in the second, before Heimgartner bettered him with a 1:41.8913s.

Heimgartner was in turn knocked off by team-mate Bryce Fullwood (#14 Middy’s Camaro), Tickford Racing’s Cameron Waters (#6 Monster Energy Mustang), and DJR’s Anton De Pasquale (#11 Shell V-Power Mustang).

However, as the field started to switch to slicks, he stripped more than five seconds off his personal-best to pull clear with a 1:33.3653s in the R&J Batteries Camaro.

That lap came just before a red flag period, the reason for which is unclear although it is worth noting James Golding (#31 Nulon Camaro) was last to return to the pits, before cars headed out again just as the fourth hour was about to begin.

Another flurry came then, with Additional Driver Jamie Whincup clocking a 1:33.3346s in the #88 Red Bull Ampol Camaro before Heimgartner hit back with a 1:31.6559s.

Matt Payne then wheeled the #19 Penrite Mustang to a 1:31.6004s, only to be knocked off by Grove Racing team-mate David Reynolds on a 1:31.4801s in the #26 Mustang.

Erebus Motorsport’s Will Brown then shifted the benchmark to a 1:31.1405s, before Heimgartner got all the way down to a 1:29.8268s with just over a dozen minutes to go in the morning session.

Behind the top four of Heimgartner, Brown, Smith, and Davison with the 240-minute hit-out done is Reynolds, Team 18 duo Mark Winterbottom (#18 DeWalt Camaro) and Scott Pye (#20 Hino Camaro), Payne, Macauley Jones (#96 Pizza Hut Camaro), and Brodie Kostecki (#99 Coca-Cola Camaro).

Car #88 sits 12th on a 1:31.9159s although it is unknown if Broc Feeney or Whincup set the time, with Golding 13th on a 1:32.0598s set after the red flag period.

Two of the high-profile entries sit outside the top 20, with the #25 Mobil 1 Optus Mustang of Chaz Mostert in 22nd and the #97 Camaro which van Gisbergen is sharing with Richie Stanaway in 23rd, both at well over three seconds off the pace.

The Mostert car has completed 16 laps so far, well down on the high of 69 racked up by the Fullwood Camaro, but above the 10 notched up so far by Tickford’s #55 Castrol Mustang of Thomas Randle, which is classified 25th with an unrepresentative slick tyre time.

Session 2 starts at 13:00 local time/AEDT and is set to run for another four hours.

Results: Morning

Note: Timesheet only showing a car’s primary driver