A classic Ford GT40 race car once owned by Hollywood's "King of Speed" Steve McQueen has become the most expensive American car ever after fetching US$11 million (NZ$13.58m) at auction.

The 1968 classic sports car, which won its 1967 racing debut at Spa in the hands of Jacky Ickx and Dick Thompson, was bought by McQueen as a camera car for his 1971 racing classic, Le Mans.

McQueen, who had become famous for his live-action action chase scene in Bullitt through the streets of San Francisco in a brand new 1968 Ford Mustang, had the GT40's roof removed and the doors hacked up to fit cameras and other gear.

The result was not easy to handle at nearly 250 kilometres per hour and described one driver as "diabolical" but it was used in that state for about five months until Le Mans filming was complete.

The chopped up car - chassis P/1074 - was later restored from 1972 onwards and with March 2013 marking 50 years since Ford instituted the GT40 program, one buyer has had no problem parting with NZ$13.5m for the classic.

It was sold fitted with an original, period correct GT40 Ford 289 cubic inch V8 with Gurney-Weslake cylinder heads and four Weber twin-choke carburetors.

Auctioneers, RM Auctions, described the purposeful mid-engine GT40 sports coupe as "the finest Anglo-American supercar of the last century, with four straight victories at the Le Mans 24 Hour endurance race between 1966 and ’69.

"In 1966 alone, it finished 1-2-3 against Ferrari, in one of the most memorable photo finishes in the race’s distinguished history, cementing the car’s place in motorsports history and on the postered walls of teenaged bedrooms the world over."

RM Auctions racked up more than US$90 million in other rare and collectable vehicles at the auction including a 1962 Ferrari 250 GT SWB California Spyder (US$8.58m); a 1955 Ferrari 410 S (US$8.25m); a 1956 Ferrari 250 GT LWB Berlinetta ''Tour de France'' (US$6.71m); a 1938 Horch 853A Special Roadster (US$5.17m) and a 955 Aston Martin DB3S that reached US$3.69 million.

As staggering that total is, it was beaten by another US motoring auction house over the weekend. Gooding and Company's total for a two-day sale was put at US$133m, while the top seller was a Mercedes 540K Special Roadster featured on this website last week. It went for US$11.7m, while a rare 1957 Ferrari California LWB Prototype Spyder went in a single-bid purchase for US$6.6m.

Gooding also sold another Spyder, a 1960 250 GT California LWB Competizone for an eyepopping US$11.2m. The weekend's other top sales included a 1955 Ferrari 410 S Berlinetta for US$8.2m, and 1956 Ferrari 250GT TdF Coupe for US$6.7m, a 1955 Ferrari 857 Sport for US$6.27m, a 1928 Bentley Le Mans for US$6m and a 1972 Porsche 917/10 Spyder for US$5.8m.

Overall, the weekend's US motoring auctions are said to have produced a dizzing total of around US$230m with 754 of 1217 lots sold at an average price of US$345,272.

- © Fairfax NZ News