REV-HEADS have broken a Guinness World Record for the largest simultaneous burn-out, with 69 hotted-up cars tearing rubber at Summernats 26 in Canberra on Friday.

The huge record-breaking burn-out lasted a full 30 seconds and spewed burnt rubber and smoke fumes into an estimated 10,000-strong crowd at the street machine festival.

Guinness World Records' Chris Sheedy told reporters the burn-out smashed the previous record of 49 cars.

He said it was a typically Australian world record, and if someone in another country broke it, Australians would be offended.

Summernats 26 will continue throughout the weekend in Canberra.