IMSA Camel GT, GTO, GTU, GTX and GTP. These categories may sound familiar to you if you like American road racing and were around back in the seventies and eighties mainly. Yeah, America did produce some of the most fantastic road racing possible and that was mainly due to the IMSA or International Motor Sport Association and their creator, John and Peggy Bishop as well as Bill France Snr. putting together the championship for 1971.

The initial story was to replicate the European road racing categories but in the USA with the FIA Touring Car categories, Group 1 and Group 2 as well as Grand Touring with Group 3 and Group 4 getting their own playing field there. Of course, it didn’t stay during its whole history as regulations did evolve and also evolution meant adapting the categories to the American market. But all in all, it saw, Touring Car, Grand Touring, Group 5 and then further evolution known by their category names such as GTO and GTU cars as well as IMSA’s own version of Group C racing, the all mighty GTP category.

The initial brief and categories were the following but as said, this was just the beginning of it. The names remained but others were added through the years as well as the whole championship initially running as a whole pack being splitted in order to have a more organized package, the best example being the GTO/GTU cars running aside from the GTP class in the eighties.

• GTO – For over 2500cc engined Grand Touring Cars.
• GTU – For under 2500cc engined Grand Touring Cars.
• TO – For over 2500cc engined Touring Cars.
• TU – For under 2500cc engined Touring Cars.

Back to the championship history, the first champions of the IMSA GT were no other than Peter H. Gregg and Hurley Haywood back in 1971 at the wheel of a Porsche 914-6 ran in the GTU class and Dave Heinz at the wheel of a Chevrolet Corvette. From the beginning, there was interest from teams, drivers but also spectators which therefore attracted sponsors. Camel was signed for the second season as the championship title sponsor and therefore, it became known as the “IMSA Camel GT Challenge Series”. Porsche went on to dominate the next years of the championship and notably with the Porsche 3.0 RSR but other European manufacturer did come and showcase their products there as well with BMW in 1974 being a great example and the lesser known fact that their car wasn’t run to Group 2 specification but to Group 4 spec. in the GTO class is another piece of history.

But as American racing is special, 1974 also saw the introduction of the AAGT or All American Grand Touring category, a special IMSA ruled category which in a way was thought to give an edge to American build cars as the European manufacturers were proving to be a bit above the rest of the domestic competition. It proved a bit of a controversy but everyone had to deal with it and well, that was the only way American cars could prove competitive as the Europeans were much more used to the Group 2 or Group 4 rules. The Chevrolet Dekon Monza was one great example of the category and probably a great answer to Europe and the Porsche dominance in the GTO category.

Next big step in the championship which was by then running strong grids of well over 30 cars was 1977 and the acceptance of turbocharged engine at mid-season as an answer to Porsche protesting the Chevrolet Dekon Monza which had won the two previous championships in the hands of Al Holbert. Rules were adapted by IMSA in order to take turbocharged but also rotary engine into account and all that was balanced with an engine displacement vs. weight formula. In the end, it all became the IMSA GTX class which was more or less IMSA’s own version of the FIA Group 5 rule set. By then, touring cars had vanished from the championship, GTs remained but Group 5 cars were more or less setting the whole picture with the Porsche 935s setting the pace and dominating the series.

IMSA was also nicknamed the “International Marijuana Smugglers Association” back in those days and here are the origins.

1979 saw the GTU class being run aside from the GTO class and it started becoming a sort of feeder series even if both would race together at particular events. 1981 saw the arrival of the GTP cars in the championship with the first one being a Lola T600, GTP was the American version of Group C but without focus on fuel economy. The cars raced altogether with the GTO class at the beginning. From 1982 as the GTP cars were holding a clear advantage over the GTO cars, it produced some of the craziest version of the Porsche 935. John Paul Sr. and Jr. through their JLP Racing team taking the title at the wheel of their twin-turbo engined Porsche 935s “JLP-3” and “JLP-4” with the later being a monocoque construction using all tricks available in the days such as true ground effect. This led to another rule change with twin-turbo engine not being allowed for the coming season and the championship GTP, GTO and GTU classes being splitted in separate races when needed from 1983 due to the growing number of entries and the need to keep the overall win for each distinct classes.

The 1971 Porsche 914/6 driven by Peter H. Gregg and Hurley Haywood IMSA GTU Championship Winning Car.

The 1971 Chevrolet Corvette driven by Dave Heinz IMSA GTO Championship Winning Car.

1975 and the GTO BMW 3.0 CSL at Riverside.

Porsche and the 3.0 RSR proved the dominant force in 1975.

Al Holbert and his All American GT Chevrolet Dekon Monza which stormed to two championship wins in 1976 and 1977.

The JLP Racing Porsche 935 “JLP-3”. A model which proved the most successful car ever in the championship.

And to drive fast, smoking camels was part of the rule !

The 1981 Lola T600 here driven by Brian Redman and which changed the championship by introducing the new GTP category.

Here is the 1982 and FABCAR built Porsche 935 “JLP-4”, the most advanced 935 ever built which led to twin-turbo engine being outlawed.

1981 and the Miller Team Ford Mustang which was nothing else than a re-bodied Group 5 Zakspeed Capri.

1982 and the Group 44 Inc. Jaguar XJR-5 the comeback of Jaguar in sports car racing was achieved in America.

1987, Riverside with Al Holbert leading the GTP and Porsche 962 packed field.

1987 again but here on a street course and the Marshall Pruett at the wheel of the Holbert team Porsche 962.

The 1989 Daytona 24 Hours Miller Highlife winning 962 in GTP trim with Derkel Bell, Bob Wollek and John Andretti.

And it was rather good for selling beers.

The 1989 IMSA GTO Audi 90 which was the first car with all-wheel drive to compete in the championship.

The F40 was also present in IMSA GTO and made its racing debut there in 1989.

Jaguar and TWR were also present in America with the XJR-10 here in 1990.

The Mercury Cougar here in 1990 and which in 1989 took the GTO title.

The GTO grid was more or less the modern Group 5 category and an action packed grid here with the Mazda RX-7, Mercury Cougar and Nissan 300ZX.

1992 Daytona 24 Hours here with the Dan Gurney and AAR built and run Toyota Eagle MkIII which would take the title that year.

1992 and the IMSA GTP version of the WSC Jaguar XJR-14.

The IMSA Camel GT Logo.

As the interest grew bigger for GTP, the cars being spectacular and powerful, it became IMSA’s premier category with a number of drivers from Europe such as Klaus Ludwig, Hans Stuck, Bob Wollek, Derek Bell and even Emerson Fittipaldi to name a few taking part in the championship. Manufacturers were there as well with Porsche establishing the Porsche 962 as the car to beat in the early years and the most reliable competition available before Nissan and Electramotive as well as Toyota and their All American Racer team ran by Dan Gurney dominated. It also saw Lola, March, Ford/Zakspeed, Fabcar, Intrepid, Jaguar and a very long list of either manufacturers or European and American officines designing their own cars for the championship in order to have their own play.

Discover the front-engined Mustang GTP story here.

1984 was a turning point in the GTO and GTU classes with the cars going from a sort of production basis to a full spaceframe construction and more or less, more and more freedom was given through the years to keep manufacturers happy and competition high. Nissan, Audi and Mercury did produce some of the most spectacular cars for the category and again, the championship proved important for the manufacturers to showcase their products. The “Win on Sunday, Sell on Sunday” was still working back then.

Discover the Audi 90 IMSA GTO story here.

As detailed here, interest for the championship and various classes or category grew bigger and bigger from the day it started back in 1971, the racing was excellent and spectacular, drivers proved very good with many Americans finding their way to Europe and world endurance racing through it. It also proved attractive for sponsors with many races being put together on street circuits and therefore bringing the show closer to the spectators as well as the full championship being showcased on TV in the golden eighties. But as competition grew bigger, costs and technology as well and the eighties golden age didn’t go over the nineties with the championship collapsing slowly from 1990 and being declared dead by 1993.

Some said it was related to the original owners, Bishop and France selling IMSA in 1989, others argued it was due to IMSA not controlling the Japanese works manufacturers efforts but well, it was probably just that times had changed. And to me, that’s pretty much where the championship history stopped, even if IMSA did still continue…