Day two of the 26th annual Summernats car festival in Canberra has kicked off with a successful world record attempt.

Dozens of the country's most powerful street machines rewrote the record books with the largest simultaneous burnout.

It was an incredible show of engineering, noise and muscle as 69 cars managed to maintain the burnout for 10 seconds, smothering the crowd with thick, toxic fumes.

Australian representative of Guinness World Records Chris Sheedy said it was and impressive sight.

"This is a fantastic part of my job," he said.

"A lot of it is at a desk, and when I get to come out to these events and see records happen, I'm as excited as anyone else in the crowd."

Mr Sheedy said today's attempt broke the previous record by 19 cars.

"The record that was being attempted today was the largest simultaneous burnout," he said.

"The amount they had to have to break the record was 50 cars and they had 69 cars that started the event.

"They had to all be burning-out for a minimum time of 10 seconds, and they successfully did that for a new record of 69 cars."

The record burnout smothers spectators in smoke and fumes. ( AAP: Lukas Coch )

But Mr Sheedy was not sure if Summernats would make another attempt next year.

"I think they're so burned-out from doing so much work on this event that they're going to have to relax for a few weeks and then make a decision," he said.

Former Summernats owner Chic Henry was today seen taking in the sights and smells of the event he once ran.

He says he supports the family-friendly initiatives introduced to the festival.

"I absolutely support the new owner's vision," he said.

"It's quite right to make it a family-friendly event... I think anything that we can do to attract families here, because it's a sensational event in Canberra."

More than 80,000 people are expected to attend Summernats events before the festival ends on Sunday.