The Kiwi took a pair of trophies away from Sydney Motorsport Park as Volvo's pace-setting Valvoline Racing team collapsed in a heap following a new practice lap record for young gun Scott McLaughlin.

Van Gisbergen led fellow Holden drivers Garth Tander and Craig Lowndes home in the first heat before Ford's Chaz Mostert and Holden's championship leader Jamie Whincup chased him to the flag on Saturday afternoon.

"I hate driving in the wet but for some reason I'm all right at it," Van Gisbergen said. "It rained almost every race in Formula Ford back in New Zealand ... sitting in an open-cockpit car, that was the worst."

Whincup reached a career milestone with his 58th pole position in the series, one that took him ahead of the late Peter Brock as the greatest qualifier in Australian touring car history.

"It's a hard one to put into words - certainly I'm quite proud of the achievement," Whincup said. "There's no greater feeling for a racing driver than to put new tyres and new brakes on a well-balanced car and just go out and milk the thing for all it's worth. [But] we can't compare the past to the present - it's certainly a different era."

The Red Bull driver built on his championship defence with fourth and third place results as key title rival Mark Winterbottom struggled in the rain.

Yet Whincup said he was not concerned by who would lift the series trophy in December.

"I'm not thinking about the championship at all," Whincup said. "It was dog eat dog, I was trying to win that race, [but] the best I could do was third. We'll worry about all that stuff later in the year."

Chaz Mostert was the sole source of joy for Ford as Winterbottom, hamstrung by ill and absent race engineer Grant McPherson, struggled outside the top 10.

"It's like there's a bit of a mocker on him at the moment," Mostert said. "He's not getting the results he needs for the championship."

Mostert was awestruck to finish on the podium in his first wet V8 Supercars meeting.

"I was quite surprised to be up that far," he said.  "I couldn't quite get [Van Gisbergen] in the end - he's really quick in the rain.

"It's awesome to follow these guys around and see what they do and pick up little things and try to do it a little bit better."

Volvo Cars Australia boss Matt Braid watched as McLaughlin went from front-row favourite to anonymous also-ran in both races. An engine failure cruelled his chances in the first race while challenging for the lead.

The team worked feverishly to replace his motor in time for the second heat, forgetting to tighten a right rear wheel nut in the rush to ready the car.

Team boss Garry Rogers was not impressed.

"That's the way it goes, unfortunately," Rogers said. "We left the wheel loose. It's unfortunate, but that's what happened. It's a new day tomorrow."

McLaughlin's Swedish teammate Robert Dahlgren finished second-last in the first heat before crashing ignominiously out of the second race.

Volvo's consolation is that the cars are speedy and they have rubber to burn in Sunday's 200 kilometre race. Teams have a limited number of tyres for each meeting, and failing to finish both races could give McLaughlin an edge in the final heat.

That factor escaped Van Gisbergen as he celebrated victory by spinning his wheels with spectacular drifting across the circuit that he later rued.

"I think we only get three sets of wet tyres for the weekend. I probably shouldn't have done skids at the end there," he said. "If it's wet tomorrow it will be exciting. Hopefully it pisses down all day."