Supercars championship leader Scott McLaughlin will have to start Sunday’s Sandown 500 from the rear of the grid after an engine rule breach at last month’s Bathurst 1000.

Stewards announced on the morning of the 500km endurance race that McLaughlin’s Ford Mustang had run an engine during qualifying and the top 10 shootout at Bathurst which “exceeded the maximum permitted valve lift” under regulations.

As a result McLaughlin and co-driver Alex Premat, who qualified fifth for the Sandown race, will now start alongside Shane Van Gisbergen and Garth Tander at the back of the grid.

DJR Team Penske have also been fined $30,000 for the breach while McLaughlin has been stripped of his pole position and lap record from Mount Panorama.

The New Zealander will however retain his Bathurst victory after DJR Team Penske changed the engine in his Mustang before the 1000km race.

It’s the second fine issued to DJR Team Penske following the controversial Bathurst weekend, with a partially-suspended $250,000 fine and the loss of 300 teams’ championship points being imposed after Fabian Coulthard was directed to hold up the field during a late safety car.

Coulthard was told to exercise “extreme caution” and warned of “debris” in lap 135 of the race, slowing the field enough to allow leading duo McLaughlin and Jamie Whincup to pit without conceding track position.

In a statement DJR Team Penske on Sunday emphasised their belief McLaughlin’s engine was within regulations and it was never their intent to break any rules.

“As the lift now measures a few thousandths of an inch high on a few valves, we can only conclude that either the engine wasn’t measured properly when it was initially assembled or the damage that occurred in the engine contributed to a change to the maximum valve lift in the forward cylinders,” the statement said.

“We apologise to Scott, Alex, our partners and our supporters, and we will continue to focus on winning our second consecutive Virgin Australia Supercars Championship.”

Despite the penalty McLaughlin is still in the box seat to wrap up this year’s title race at Sandown.

The 26-year-old has a 500-point championship lead over Van Gisbergen and needs to be 300 or more points clear after the race to have an unassailable advantage.

If Van Gisbergen wins the race, even a 25th-place finish for McLaughlin would give him enough points to secure back-to-back championships.

Sunday’s race begins at 1.25pm.