Talladega speed record - The 917's most outrageous feat

It would be one of his final acts and was overshadowed by his death. Just 10 days after Mark Donohue had set a famous record, a tyre failed on his Penske-run March 751 during practice for Formula 1's 1975 Austrian Grand Prix and sent 'Captain Nice' into and over the catch fencing at the Hella-Licht Kurve.

He initially seemed to have escaped but, after complaining of headaches, was admitted to hospital, lapsed into a coma from a cerebral haemorrhage, and died two days later.

But before that tragic turn of events, Donohue had set what at the time was the fastest lap ever recorded on a circuit, storming around the Talladega tri-oval at a staggering 221.120mph aboard the Porsche 917/30 in which he had dominated Can-Am in 1973.

Those figures become all the more daunting when you consider the tumultuous journey that car had undergone, pushing Donohue to the edges of his patience and testing every inch of his famous technical knowledge.

Vanity record hunts tend to fall on deaf ears, but that one still resonates today. So much so that, when Porsche canned its World Endurance Championship LMP1 programme, the Talladega run wasn't far from the minds of the decision-makers, and the manufacturer's media and marketing team suggested a fitting farewell for a 919 Hybrid that managed three drivers' titles, three manufacturers' crowns and a trio of Le Mans 24 Hours successes.

Porsche's then-LMP1 boss Andreas Seidl explained: "One of the ideas was a record attempt, comparing it to stuff done in the 1970s by Penske. I was a bit sceptical at the beginning, as there is a risk in these records.

"But the idea was so convincing that we said, 'OK, if we can find the budget, let's go for it.'"

Soon after, it claimed a Formula 1-beating 1m41.770s record with Neel Jani at Spa in 2018, while in June of that year Timo Bernhard went around the Nurburgring Nordschleife quicker than anyone, ever: 5m19.546s.

It's unlikely that Porsche would ever have committed to such a programme if it wasn't for Donohue's - and Penske's - work to turn Porsche's 1970s turbo programme from a troublesome, nightmarish one into Can-Am domination that played a role in bringing an end to the innovative and exhilarating series.

Can-Am was (temporarily) gone by the time Donohue arrived at Talladega in 1975, and the rumour was that the run was all because of a bet.

In one run the car caught fire at the rear. It simply hadn't been designed for such flat-out running

The Penske team had been fined $10,000 for an infringement in a NASCAR race and team owner Roger Penske was allegedly keen to win back his cash from long-time friend Burge Hulett.

The bet itself was for the 917/30 to beat AJ Foyt's world record speed for a closed course, set at Talladega at 217.854mph in his Coyote-Ford USAC machine. Putting aside any flutters, this was a target Penske was convinced could be beaten, and he reckoned that the 917/30 had more to accomplish than its Can-Am dominance of two years earlier.

He convinced Donohue, Weissach head of research Dr Helmut Flegl, engine specialist Hans Mezger and turbo expert Valentin Schaffer to try for the record at Talladega.

Donohue had been coaxed out of his role as general manager of Penske Racing to have another go at F1 from late 1974, and the Talladega bid came during a run of European races in the summer of 1975, falling between the German and Austrian GPs.

When he was at Talladega, he was far from happy. Donohue had shown annoyance that the 917/30 had kept blowing engines in testing - which had begun in January - and in one run the car caught fire at the rear. It simply hadn't been designed for such prolonged flat-out running and its 5.4-litre turbo got extremely hot.

Porsche developed some special intercoolers, but even then the engineers were allegedly not quite brave enough to keep the engine at full power on the dyno for the required two minutes...

"The g-forces are strange at that speed. It gives you the tendency to fall asleep, to forget who you are and where you are" Mark Donohue

The video of the attempt - worth digging out on YouTube - is a scary watch. Donohue describes being unable to keep his foot planted throughout the lap and reports the steering being "fragile" and "very light". Penske remarks that, to beat Foyt's record, Donohue must find two tenths on a 2.66-mile circuit.

And do it while coping with a gust of wind at Turn 2 that would attempt to push the car around.

"Going into the first turn is an eerie feeling," Donohue told reporters at Talladega. "I was a little chicken and got what we call 'balloon foot'.

"The g-forces are strange at that speed. It gives you the tendency to fall asleep, to forget who you are and where you are."

And yet, weird sensations and all, he did it. Donohue lapped at a stunning average speed of 221.120mph.

"I don't think this is an ultimate speed here as far as the track is concerned, but there is a limit for technology," said Donohue. "This type of car was not built for high banks. It was set up for 200mph on the Can-Am circuit."

Cue catcalling from Indycar and NASCAR. Foyt reckoned he could take his Indycar, make a few adjustments, and beat the record, while noises from NASCAR suggested some radical engineering tricks on a stock car could smash Donohue's record.

Donohue was ready for such efforts: "If someone beats my record, I'd love to come back and try again. But I can assure you, it will be in a completely different looking car built to set a record here."

No car has ever gone faster around Talladega, but the record was later beaten elsewhere. By then, Donohue was no longer around to respond, and the 917/30 had earned its retirement.

This week's Autosport magazine is dedicated to a special celebration of the Porsche 917, the car that launched Porsche as a Le Mans force and killed Can-Am