"Dare to dream, and wow, here we are," he said, sipping at a celebratory beer as a crowd gathered around his title-winning Chevrolet Impala.

Mr Sorensen, from Peak Crossing just outside Ipswich, has somewhat of an advantage over some of his rivals in that he runs a custom car workshop and was able to build and prepare the Impala using those resources.

He has owned the left-hand drive coupe for around 10 years but this was only its second Summernats appearance.

"Last year we just missed out on the top 10 in the elite [category]," he said.

"And the only time I had driven it was down the road after the show."

In order to win what is described as the "holy grail" of Australia's custom car awards, the winning car must be both judged as elite in quality and perform strongly in the on-track driving events as proof of its engineering.

Mr Sorensen's street-registered V8 Impala carried the number plate "tribute" to acknowledge his uncle, Bruce Sorensen, who died of melanoma two years ago.

"Before he passed, uncle Bruce gave me his hot rod which I'm going to start work on now and hope to bring to Summernats next year," he said.

Two Canberra cars finished among the Summernats award winners.

Tomi Vatavuk's 1974 XB Falcon sedan won the top engine bay award in the street cars category, while Harvey Miles' extraordinary 1963 EH Holden Premier won "top authentic".

Mr Vatavuk, an IT contractor from Watson, said his Falcon was built to be a street cruiser in which he could take his family.

The car, sold from new by the now-defunct Gregory's Ford dealership in Braddon, has been a methodical 10-year build in which Mr Vatavuk has acquired specialist skills along the way.

"I wanted to have a particular strut top design so I taught myself how to use computer-aided design and then had each of the tops milled from a single billet of aluminium," he said.

Mr Miles' hot pink EH Holden has a remarkable history. When he first bought the car he though the paint colour was some previous owner's idea of a joke respray choice.

But when he delved into the car's history, he was surprised to find it was a one-of-a-kind factory colour.

"Holden ordered the paint, which was a special Cadillac colour, out of USA as a surprise for the new general manager who was brought out to run the car factory in South Australia," he said.

"The car was nicknamed 'Blondie' by the assembly line staff, and it stuck."

The car was restored almost entirely within Mr Miles' garage in Kambah.

Summernats was shrouded in smoke and controversy as it wound up with one of the smallest Sunday crowds in many years. Hundreds of campers at Exhibition Park packed up and went home early as the choking, hazardous smoke from the NSW bushfires descended on the event.

However, entrant numbers were reported as 2200, which is the second-highest total seen at the event. Over 100,000 people came through the gates over the four days.

On Friday, a combination of predicted record-breaking heat and public anxiety about the event's burnout competition under such conditions opened a rift between Summernats and ACT Chief Minister Andrew Barr.

Mr Barr had requested Summernats to suspend or cancel the Saturday burnouts which Summernats co-owner Andy Lopez said "completely blindsided us [the organisers]".

"I got a phone call mid-morning to say I would get an email from the deputy Chief Minister asking us to consider re-scheduling the burnouts," he said.

"I said that was impossible and wanted the know the basis on which it should be shut down. The reasons weren't clear. Was it smoke? Was it fire? Was it public anxiety?

"We were incredibly well-prepared to manage a safe burnout event."

The competition proceeded and at times it was difficult to distinguish between bushfire haze and tyre smoke, particularly during the finals on a cooler, smokier Sunday afternoon.

Just over the border in Sutton, an ugly Friday night incident saw thousands of people, some wearing Summerants wristbands, gathering to watch drivers doing burnouts on the street.

Vision posted to social media showed people in thongs walking alongside and even holding a car as its spun and smoked its tyres.

Police described the activity as "incredibly dangerous".

However, when police attended and attempted to disperse the crowd, they were pelted with rocks and bottles.

Mr Lopez roundly condemned the behaviour, describing it as "mind-bogglingly stupid".