Luke Youlden posted a 1:58.670s effort during an entertainment session for the $1.8 million Australian-built supercar around the famous 6.2km circuit.
Youlden's time eclipsed the outright lap record (1:59.2910s), held by factory Audi driver Christopher Mies, by 0.621s.
Mies set the official outright record during the Challenge Bathurst event in November last year.
While the Brabham BT62 lap has beaten that time it will not be classified as a new lap record given it wasn't set in an official competitive session.
However, the feat remains an impressive moment in history as the Brabham becomes the fastest sportscar to lap the circuit.
Youlden admitted it felt ‘pretty cool' to have set the time and believed the Michelin shod car could drop into the 1:56s bracket.
“I'm happy to beat he record but disappointed we didn't smash it,” Youlden told Speedcafe.com.
“I'm peaking but at the same time I'm a little bit disappointed because we had a few little hiccups; I could go faster.
“It will well and truly do a 1:57s and maybe a 56s.
“It feels pretty cool, it almost make the GT3 car feel like a production car as we are going five or six seconds quicker, it's pretty insane.”
Speaking to Speedcafe.com after the moment, he declared the time an incredible achievement.
“It is an incredible achievement. There is slight relief but I'm also excited not just for me but for the whole group who have worked on this project.
“To have Brabham back on a race track where it belongs is a special moment.
“This just validates all the hard work that has been put in.
“I think there is definitely more time in the car. It is something the car can be proud of.”