Race Weekend Central

Charlie Kemp’s Roush-Powered 212-MPH IMSA Mustang II

In the mid-1970s, Bill France’s International Motor Sports Association (IMSA) had a problem. Though the organization sanctioned the United States’ greatest sports car races, the cars themselves were a lot less American than the tracks they raced on. 

After the big American automakers slashed their racing budgets during the oil crisis of 1973-74, the series was utterly dominated by Porsche. Twenty-one of the 51 entries in the 1975 24 Hours of Daytona were 911s, a race where the German marque locked out 13 of the top 15 positions. As legends Hurley Haywood and Peter Gregg took the checkered flag in a Brumos 911, the highest-placed American car was an AMC Gremlin in 17th.

To give the fans some home-grown, high-displacement heroes to cheer for, IMSA introduced the All-American GT class midway through 1975, its ruleset catered to privateers like John Greenwood, who tackled the high banks of Daytona with a series of scary-fast-but-unreliable Corvettes. It was the DeKon-prepared Chevy Monzas, little coupés fitted with box flares, big wings, and fuel-injected GM V8s that eventually dethroned Porsche in the series championship in 1976 and ‘77, but it was Ford’s answer – or technically, Charlie Kemp’s Ford-flavored independent answer, that most pushed the boundaries of what was possible under the rules of AAGT.

Kemp was a former dirt oval and drag racing champion who, based on an uber-successful stint in Sports Car Club of America (SCCA) racing in a secondhand Shelby GT350 (pictured), converted his skill behind the wheel into a successful stint in Can-Am with Porsche. 

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Kemp was initially tapped by Mark Donohue to join a new Monza-based IMSA program in ‘76, but after Donohue’s death in an F1 practice crash in mid-’75, he went his own way. After signing with Dobbs Ford (a dealership in Memphis, Tenn.) Kemp got to work on what would soon be called the Kemp Cobra II. 

“Soon” is the operative word. Kemp and Jimmy Dobbs began designing the Cobra II in November of 1975, with less than two months before its scheduled debut at the 24 Hours of Daytona.

Dobbs donated a stock Mustang II, and Kemp used its bodywork to shape the molds for the custom fiberglass panels of the racecar. They sourced a 351 Cleveland V8 modified by then drag-racing specialist Jack Roush – the very beginning of Roush’s long career in sports cars – and a four-speed Toploader transmission from a Winston Cup car. As required by the rules of AAGT, the suspension design – A-arms up front, live-axle out back – was based on the stock Mustang II, but the 12.2-inch ventilated disc brakes were at the cutting edge of racing technology.

All-in, Kemp’s Mustang II racer was 4 inches shorter, 4.3 inches wider, and 7 inches lower than the car Dobbs had donated. The name and the paint job were an homage to the Shelby in which Kemp had made his name. 

Despite IMSA officials overseeing the build, when Kemp and co-driver Sam Posey showed up for scrutineering, they were told the Cobra II couldn’t race. But Bill France, wanting to show fans “Chevrolet vs. Ford vs. those foreign cars,” created the Le Mans GTX – for “Grand Touring Experimental” class on the spot.   

Experimental was the right word, because although the Roush 351 could power the Cobra II to over 212 mph on the high banks of Daytona, the 535-horsepower monster had a bad habit of blowing itself up. While the Kemp Cobra II won its class by default in 1976, it placed 70th overall. The Gremlin was 42nd.  

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In its six starts (from 15 races) in 1976, the Cobra II earned three top 10s and two top fives, including a runner-up finish in the season finale at Daytona. Remarkably, that was the only race in which the car was scored as running at the finish – even in its fifth-place result at Ontario, the car didn’t make it to the checkered flag.

Kemp campaigned the car sporadically over the next three years, never scoring better than seventh and more often than not finishing the day in the garage – even after switching to the more reliable Australian variant of the 351.

Kemp called it quits on the Cobra after breaking a gearbox in qualifying for the 1981 Daytona 24. By that point, the Mustang II had been out of production for three years, condemned to the scrap heap of history as an automotive punchline. 

From our modern age of spec hybrid systems and Balance of Performance, the Kemp Cobra II is a reminder of a different time in sports car racing, the years when a couple ingenious independents could transform an economy car into a boundary-pushing racing machine. Yet it’s also a reminder that we tend to view racing’s past through rose-colored glasses. After all, the Kemp Cobra II failed to finish in all but two of its IMSA starts, and never won a race. 

Yes, the story of the Kemp Cobra II reminds us to appreciate what we had then, but it also assures us that the IMSA we have now is pretty darn good. 

Coverage of the 2023 Rolex 24 Hours of Daytona begins Saturday, January 28th at 1:30 p.m. ET, on NBC, Peacock, and IMSA TV.

About the author


Jack Swansey primarily covers open-wheel racing for Frontstretch and co-hosts The Pit Straight Podcast,but you can also catch him writing about NASCAR, sports cars, and anything else with four wheels and a motor. Originally from North Carolina and now residing in Los Angeles, he joined the site as Sunday news writer midway through 2022 and is an avid collector (some would say hoarder) of die-cast cars.

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