Brodie Kostecki claimed a maiden Dunlop Super2 Series victory in a dramatic Sandown opener, with first-across-the-line finisher Garry Jacobson penalised.
Jacobson greeted the chequered flag, but was demoted to 18th by a 15-second penalty incurred early in the race for contact with Kostecki.
Kostecki fell to fifth but regrouped to keep series leader Paul Dumbrell at bay on the run home, while rookie Thomas Randle rounded out the podium.
The race began behind the Safety Car, for two laps, due to the wet weather with the field on slicks.
Jacobson passed ARMOR ALL Polesitter Chris Pither into Turn 1 when racing started, and was then challenged by Kostecki into Turn 12 later in the lap.
Kostecki was forced wide, dropping to fifth as Pither retook the lead from Dumbrell, with Jacobson third but copping a 15-second time penalty.
Dumbrell slipped by Pither and into the lead on lap six, with Pither then spun by Will Brown at Turn 2 on lap eight.
The pair could not escape the wet grass, bringing out a Safety Car period and eventually finishing 16th and 17th.
Kostecki passed Dumbrell into Turn 1 at the restart, but was himself overtaken by Jacobson at the same place on lap 14 of the 20.
Jacobson stayed there but could not get more than 15 seconds clear of the pack to keep the win, Kostecki remaining a close second to take the win while Jacobson dropped to 18th.
Dumbrell crossed the line 0.6628s behind Kostecki and extended his points lead from 136 to 217 over Pither.
Randle was a further two seconds adrift to round out the podium in his Tickford Falcon.
He picked up that spot after a pair of last-lap clashes between Dean Fiore and Kurt Kostecki, as they disputed third on the final lap.
Kostecki fell to 20th, while Fiore crossed the line fifth but was handed a 26s penalty that demoted him to 19th.
Alex Rullo and Macauley Jones came from 12th and 14th on the grid to finish fourth and fifth, ahead of Jake Kostecki.
Jack Smith, Dominic Storey, Matthew Chahda and Bryce Fullwood rounded out the top 10.
Shae Davies spun out of 10th early, had a trip through the gravel at Turn 9 mid-race and then collided with Nathan Morcom at Turn 1 in the closing stages.
He was the last driver classified in 22nd, with Morcom retiring due to damage.
ARMOR ALL Qualifying for Race 2 will take place at 9:15am on Sunday, followed by Race 2 at 12:10pm local time, as part of the RABBLE.club Sandown 500.