Forty years ago, an automotive upstart called AMG raced a Mercedes-Benz sedan in the 24 Hours of Spa-Francorchamps. It was an unusual entry for the company’s first race, and few expected much from it. But the big Benz blew the doors off almost everything in its path and finished second, instantly establishing AMG’s credibility as a tuner.

This weekend, Black Falcon racing and AMG pay tribute to that car when they compete at Spa in a Mercedes-Benz SLS AMG GT3 wearing identical livery. To complete the homage, one of the three men driving the car will be Kenneth Heyer, whose father Hans Heyer was at the wheel of that legendary AMG sedan four decades ago.

“Forty years after our class victory and second overall place, I think it is a great idea to enter the Spa-Francorchamps race with the SLS AMG GT3 in the same look as ‘my’ 300 SEL,” Hans Heyer said in a statement. “Naturally I wish the Black Falcon team and my son Kenneth every success – and will be delighted if he wins at least second place!”

The AMG SLS “Gullwing” is a natural for racing, given its monstrous power and sublime handling. That’s why you’ll see seven of them on the grid this weekend. But the luxurious 300 SEL 6.3 was as unusual a candidate for racing as you might imagine, what with its four doors and power steering and air suspension. Hell — it even had carpet on the floors and wood on the dash.

AMG is synonymous with performance nowadays, but the company was just four years old in 1971 and had something to prove. The 300 SEL 6.3 was Germany’s fastest production sedan, and the wizards at AMG put it over the top. They bumped the displacement to 6.8 liters and tweaked the engine to produce 428 horsepower and 448 pound-feet of torque. Aluminum doors helped cut the weight to 3,637 pounds, but that was still a lot of mass for the car’s disc brakes to handle. They strained to bring the car down from its top speed of 164 mph.

“But on the old Spa course the brake discs had plenty of time to cool down, and nobody could catch us on the long straights,” Heyer said.

Heyer and co-driver Clemens Schickentanz surprised almost everyone when they qualified fifth out of 60 cars. The only Mercedes on the grid lined up alongside cars driven by the likes of Peter Hoffman, Niki Lauda and Hans Stuck, and it was in third place by the end of the first lap.

After 24 hours and 308 laps, Heyer crossed the line just behind the Ford Capri driven by Dieter Glemser and Alex Soler-Roig. The big Benz placed first in its class and second overall, a feat that instantly established AMG’s credibility.

“It was certainly a sensation at the time,” AMG founder Hans Werner Aufrecht said.

The car competed in several more endurance races in 1971 and ‘72 but was forced into retirement in 1973. A change in the rules limited displacement to 5.0 liters, making the car obsolete. AMG sold it French conglomerate Matra, which used it for high-speed tests of aircraft tires.

No one knows what became of the car, and the racer shown here is a replica AMG built in 2006.

Photos: Mercedes-Benz

The old, with the new. The AMG SLS Gullwing GT3 wears the same color, number and sponsorship decals as the 300 SEL 6.8 that established the tuner’s reputation.

Kenneth Heyer with the AMG SLS he will race on the same track where his father, Hans Heyer, helped AMG establish its reputation with the 300 SEL.

The Black Falcon racing AMG SLS GT3 is one of seven Gullwings that will line up for the 24 Hours of Spa-Francorchamps this weekend.