IMSA GTP - The Prototype Golden Era

In Early January, 1977, two cars turned up to the 24 Hours of Daytona, fielded by the Inaltera Motors team. Ford Cosworth V8 power launched the cars to 3rd and 4th on the grid. Although both cars did not finish, in result of an accident and a suspension failure, they caught the attention of the spectators there, and International Motor Sports Association (IMSA) President John Bishop. Bishop was intrigued by the cars unusual design, and felt that if given a class, could intrigue the American public.

The current fastest class in IMSA was the GTX class, which was based off the FIA Group 5 category, and likewise was being dominated by the Porsche 935. The cars hadn’t captured the public attention as it had overseas, and the American public had become bored watching just the 935 dominate. Bishop decided it was time for a new class, one that would be for purpose built race cars and that would be developed alongside the FIA Group C class. With one exception, there were no fuel restrictions, the cars could be as powerful as the manufacturer desired. The Grand Touring Prototypes (GTP) class was born.

For 1981, the GTX class would be abolished, and GTP would be phased in, absorbing all GTX cars, including the Porsche. The early cars were unreliable and couldn’t compete in the endurance events at the beginning of the season, with the Porsche 935 winning the season opening races at the Daytona 24 Hour and Sebring 12 Hour. However, development had began in Late-1980 for a new car, one that would prove to be GTP’s first dominant car.

The Lola T600 started development with driver Brian Redman. The T600, which was based on the T70, was fitted with new bodywork and a 6.0L V8 Chevrolet Engine, developing around 600hp. Lola hired aerodynamicist Max Sardou to work the underbody to harness a new aerodynamic concept, ground effect. Put into practice by Jim Hall and perfected by Collin Chapman, the ground effects on the T600 would set the stage for just what GTP would become.

Although the T600 didn’t debut until the fifth round of the season, a 100-mile race at Laguna Seca Raceway, it still set the pace when it arrived. It won its first race, and after winning races at Lime Rock Park, Mid-Ohio Sports Car Course, Portland International Raceway and Road Atlanta, Lola had sold 12 more T600’s. Cooke-Woods Racing and Redman dominated the season, dethroning Porsche for the fist time since 1977.

Redman and Co-Owner Roy Woods left the Cooke team for 1982, and the team wouldn’t return to dominance, leaving 1982 open to all. J.L.P. Racing and Cord Racing returned to the GTP field in Lola’s for 1982, joined by the Interscope team, with drivers Danny Ongais, Ted Field and Bill Whittington. Interscope’s cars won four races in 1982, but John Paul Jr. won the IMSA Championship, driving both a Porsche 935 and Lola T600 throughout the season, getting one of his seven wins in a Lola. Interscope’s Ted Field finished second in the Championship.

For 1983, teams would start investing more into the GTP class, giving it life. March would offer their 83G, most notably driven in a Red Lobster livery by Kenper Miller and David Cowart. Aston Martin would field two Nimrod NRA/C2’s, with one being driven by Darrell Waltrip and AJ Foyt. Finally, the Group 44 team would field a Jaguar XJR-5, with backing from Jaguar itself. The Lola’s would also make return appearances, with Interscope fielding T600’s with new turbocharged Chevrolet V6’s that provided an extra 100hp over the V8. Sans Bayside Racing, all other Lola’s used the older V8’s. Bayside installed a Porsche 935 turbo engine in their T600 to find extra speed. With that, the mix of engines and chassis would go at it with the still-present Porsche 935 at the 1983 24 Hours of Daytona.

It was all for not though. The Porsche 935 still won both the GTP Class and overall, extending their streak to six wins in a row at Daytona. The Interscope team saw one of their T600’s go up in flames before the race started, and the other saw a turbocharger failure on Lap 47. One Aston grenaded just after the twelve hour mark, while the Foyt/Waltrip Aston Martin saw an engine failure four hours in and the Group 44 Jaguar crashed just nine laps later. Foyt was tapped to drive what would become the winning 935, much to the protest of lead driver Bob Wollek. The highest finishing purpose-built Prototype was a March, finishing six laps behind the Porsche, but it was enough to cement the class.

The 1983 season became one dominated by March, with Al Holbert winning the Championship in a car that started the season powered by a Chevrolet engine, and ended with a Porsche engine. However, the 1983 season saw even more factory investment late in the season, this time from home.

Ford became interested in the GTP class from the beginning, as the Mustang GTX had almost become obsolete. Bob Riley, future builder of Riley Prototypes, was tasked with designing the car. It was unusual to say the least. Rather than the traditional mid-engine setup, the car had a front mounted Cosworth Straight-Four with a body was fitted by Roush Performance. Three cars would be made to finish out the season, with the Mustang’s first race being the Road America 500. The planned 2.1 Liter Four-Cylinder wasn’t going to be ready by then, and they would use a 1.7 Liter Four-Cylinder for the finish of the 1983 Season. Its debut at the rainy Road America 500 was successful to say the least. A team of Tim Coconis and Klaus Ludwig took the overall victory, and a team of Bobby Rahal and Geoff Brabham finishing third. The next nearest GTP car was a T600 fielded by Conte Racing.

The Mustang’s second race wouldn’t fare as well. At Pocono Raceway, Ludwig’s car lasted just eight laps before retiring, and the Brabham car retired after only 49 Laps. Group 44 team propelled their Jaguar to the overall victory. Roush Racing pulled out of the program, as Roush wanted to place a V8 into the massive front end of the Mustang, and Ford wanted to advertise their four-cylinder-turbo engines. Only one Mustang turned up to the final race at Daytona, running under the Zakspeed USA banner with Ludwig and Rahal sharing the car. The Mustang retired after only 53 Laps, finishing in 49th place.

Ford wouldn’t attempt to enter the Daytona 24 Hour, as they attempted to improve reliability in their 2.1L Four-Cylinder. One other manufacturer would debut a new car at Daytona: Porsche. The German manufacturer who had still won races in the 935 had chosen to debut their new Prototype at Daytona. The drivers? Second and third on the American Open Wheel All-Time wins list, Mario and Michael Andretti, with Shell as the sponsor. The Porsche 962 was born.

The 962 would go up against the new March 84G, with Porsche, Chevrolet and even Buick power, more Nimrod Aston Martins, a Mazda powered Argo JM16, more Lola T600’s, a BMW-Sauber C7, a Mazda-powered Lola T616, a Ferrari 512 BB/LM, a factory Mazda GTP and, not to mention, a plethora of Porsche 935’s. The 1984 Daytona 24 Hour became a war. That war had an outcome much the same as what the 1983 season had left off with Kreepy Krauly Racing taking victory in a Porsche-powered March 83G. GTP cars took eight out of the top ten spots in the overall finishing results, much different than previous years in which GTO cars had finished up front. The GTP class was coming into its own.

The debuting 962 did brilliantly, dominating the race until the car retired on Lap 147 with engine and gearbox issues. However, it had proved itself worthy, and the 962 program set dormant until the 6 Hours of Riverside. Before Riverside, however, sat a showdown between two American rivals on the streets of Miami, and an ancient rivalry would add a new chapter. Ford vs. Chevrolet.

Even though Chevrolet had been a engine choice since the inception of the series, GM had not attempted a factory effort in the GTP class. In 1984, they saw their chance to explore the opportunities for their V8 and V6 engines and also to prove themselves against the likes of Jaguar, Porsche, Mazda and, perhaps most importantly, Ford. GM employed a team of engineers to partner with Lola to develop the new “Corvette GTP”. The first car was outfitted with a 3.4 Liter Turbocharged V6, a destroked version of the commonly used 4.3L V6, and would be fielded by the Racing Systems team.

Ford would also bring the Mustang GTP, now fitted with the 2.1L Cosworth engine, it was expected to put up a fight against the Corvette. Still reeling from the Roush departure, only one Mustang GTP and only one driver, Klaus Ludwig, would compete at Miami. Fitting as only one Corvette would compete as well. Ford and Chevrolet battled as engine partners as well, Ford’s influence spread to a Alba/Momo AR3 fielded by the Momo Corse team and a Argo JM16 fielded by Deco Sales. However, Chevrolet spread their influence to a Phoenix JG1 and a Rondeau M382, fielded by the Holly Racing and Walrus Racing teams.

It was set for battle, and when the the flag dropped, GM and Ford went at it. That is, until the now common Ford luck struck. Ludwig developed a puncture early in the race, which led to much more severe suspension damage, sending the Ford home 25th out of 30th, while the Corvette came home 13th. All the action was behind the pair of Group 44 Jaguar XJR-5’s, which took 1-2 overall.

The rest of Ford’s 1984 bid went about as well as the first part, with the team only finishing the Grand Prix of Sonoma and the finale at the Daytona 3 Hour, both in the 5th position. Ford shut down the bid at the end of 1984, with Head of Ford Motorsport Michael Kranefuss going so far as to say that “it was the worst project I’ve ever been involved in.”

The 1984 12 Hours of Sebring saw the end of an era. The dominant Porsche 935 saw its last victory with De Narvaez Enterprises. The bulletproof cars made up four out of the top five in the race, with the only exception being a March 83G fielded by Blue Thunder Racing team. Blue Thunder Racing would later go on to win the 1984 Championship with Randy Lanier. Not to mention, the Porsche 962 saw its first victory at Mid-Ohio Sports Car Course, with Al Holbert and Derek Bell behind the wheel. The 962 then went on a tear, winning five of the last eight races of the 1984 season. It was the start of a new era for Porsche.

1985 became a year of development for most manufacturers, leaving Daytona a wash for Porsche. Porsche took the top five spots, with a team of AJ Foyt, Al Unser Jr. and Bob Wollek winning. The top four were 962’s, and fifth was a 935. Most factory teams didn’t compete in Daytona, with only Porsche, Jaguar and Chevrolet arriving. Jaguar ran the customary XJR-5’s, with both falling out of the race. Chevrolet’s entry was a T711 chassis with a 5.7L V8 that made an estimated 800hp. The Lee Racing entry fell out early with a gearbox failure. Most stayed the same throughout the year. Porsche dominated, only leaving the Road Atlanta 500K for Jaguar to take victory. Porsche won every other race and took the Championship with Al Holbert.

1986 was much the same, with Porsche still dominating in the 962. However, it wasn’t for a lack of trying from the other manufacturers. Midway through 1985, Jaguar dropped their V12 from the World Sportscar Championship into their XJR-5 and called the car the XJR-6. GM, however, had tapped into their NASCAR owners to field a full-factory GTP effort. One bit: Rick Hendrick. Although Porsche won the first three races at Daytona, Miami and Sebring, Hendrick and GM bit back at Road Atlanta, winning with Doc Bundy and Sarel van der Merwe. The GM effort nearly lapped the nearest Porsche of Holbert. However, Holbert still grabbed the Championship. Lee Racing had abandoned the Corvette GTP program by Road Atlanta, but Hendrick continued on. Hendrick’s team would win again at Palm Beach, by the slimmest of margins, four tenths of a second over a BF Goodrich Porsche 962. Problems with Jaguar’s V12 secured Corvette second to Porsche in the manufacturer’s standings, but no one could dethrone the mighty 962.

Another manufacturer had also attempted entry into the season. BMW attempted a factory GTP effort, based on a March 86G chassis. The M12/14 Straight Four had a massive turbocharger strapped to it, allowing for an estimated 1,400hp in qualifying boost. The top speed was 220mph, limited by gearing. As with most hastily prepared factory cars, it was a failure to say the least. It was planned to debut at the 24 Hours of Daytona, but the only car they had caught fire at a Road Atlanta test, meaning the car was to debut at Miami. This would allow two cars, one driven by Davy Jones and John Andretti and another driven by John Watson and David Hobbs, to debut instead of just one.

The Jones/Andretti effort ended up in a wall only 41 Laps into the race, while the Hobbs/Watson effort ended up ninth overall. For the 12 Hours of Sebring, BMW attempted a third car, but after drive Bobby Rahal ended up in a major accident in practice. At Road Atlanta, only one car was to be entered, and John Watson retired it after only a single lap. It took until Watkins Glen to record a victory, but the rest of the season then became one that was forgettable in BMW’s racing history. The car retired race after race, and BMW eventually pulled out of IMSA at the end of the 1986 season.

1986 also saw the entry of Nissan into the GTP class. Nissan skipped both the 24 Hours of Daytona and 12 Hours of Sebring to develop their car, which fielded by Electramotive and named the GTP ZX-Turbo. The quite forgettable season climaxed in a third place at Portland, but was plagued by mechanical failures for most other races.

For 1987, much stayed the same at the top of the Championship. Porsche won again with the great 962, but it was a fight from there on back. After skipping the 24 Hours of Daytona, and allowing Porsche to take the top six spots, Nissan arrived with an improved ZX-Turbo (ZX-T) to Miami. They beat the nearest Porsche of Bobby Rahal and Jochen Mass by eleven seconds and lapped everyone else. However, the Nissan suffered issues at Road Atlanta, Riverside and Mid-Ohio. Although they bounced back, leading to a victory at the end of the year at Del Mar, the season plagued by mechanical troubles led Nissan to take fifth in the constructors championship.

Jaguar ran their improved XJR-7, winning at the Riverside 500 Kilometers. However, they struggled with mechanical issues for most of the season, leaving the slow but reliable Corvette GTP to take second in the constructors championship. Roush returned with Ford in a rebranded version of their Probe GTP, called the Mustang Maxum GTP, with a best finish of second at Lime Rock Park. The field seemed set in stone, Porsche first, everyone else racing for second. That is, until 1988 rolled around.

When Daytona rolled around, every team seemed like they had something new and better than the previous year. Jaguar rolled out their new XJR-9, which featured a 7.0L V12 and a low downforce package, complete with wheel skirts and all. Pontiac arrived with a Firebird GTP that ran with factory support. Ford arrived with their familiar Roush GTP, with drivers like Bruce Jenner, Arie Luyendyk and Scott Goodyear. Buick arrived with their engine stuffed in the back of several March 86G chassis. Not to mention Porsche arriving with the 962 and Chevrolet with the Corvette GTP.

For the first time in several years, Porsche would not be in victory lane at Daytona. The Jaguar XJR-9’s Castrol Factory team took overall victory by a lap over the next 962, and the other Castrol car in third. The next non-962 was the #09 factory Pontiac Firebird GTP, which finished 8th. Nissan? They didn’t show up, citing development needs on the newest version of their ZX-T and the ability to enter two of them into the Grand Prix of Miami, but the race ended in a disappointing eighth. The Dyson Racing Porsche took the overall victory over the Castrol Jaguar team and three other Porsche 962’s on the lead lap.

At Road Atlanta, Nissan took a bite, taking victory by a mere four seconds over the #60 Castrol Jaguar. The Rick Hendrick Corvette team also finished their first race of the season, with eighth place at the Braselton, Georgia road course. Porsche rounded out the podium with the Holbert Racing team finishing in third.

Nissan then took more and more bites. First at Palm Beach, then Lime Rock Park, then Mid-Ohio, then Watkins Glen, and finally Road America. Nissan had found something in their turbocharger. The technology that was developed allowed for the turbo to have boost pressure at most operating rev’s, allowing for a considerable advantage over most cars, which the boost came on hard in lower gears. Nissan finally entered their second car at Portland, and it assisted in a dominant performance, allowing for a 1-2 finish. Then the Geoff Brabham car took victory again at Sears Point, California, the final in an eight race win streak. The lone car that entered the next event suffered electrical issues and retired, leaving the door open for the Dyson Racing 962 to take victory over the #60 XJR-9.

The Nissan returned at Columbus, winning the race, but only to be defeated in the final race at Del Mar by the #60 Jaguar. Even though Nissan won nine of the fourteen races of the season, their decision to skip Daytona and Sebring allowed Porsche to take their fourth manufacturer title in a row. Geoff Brabham, however, won the Driver’s Championship by a truly amazing margin. Porsche looked to strike back, but tragedy struck at a turbulent time.

Taking note of the outdated 962’s performance compared to the newer Jaguar and Nissan, Al Holbert began to assist in development of a new car. The car would have an open cockpit and would intend to be a car for both factory and private teams to develop. However, after leaving the Columbus 500 on September 30th, 1988, Holbert’s Piper PA-60 aircraft crashed shortly after takeoff. IMSA lost one of its biggest names and arguably the most successful driver in the GTP era and the leader of Porsche’s investment into American Motorsport had passed on.

Porsche had also started to lose interest in IMSA. After attempting to build their own chassis to compete in CART for the end of 1987, they decided to go the route many had in IMSA. They bought a March chassis and developed from there. The project struggled, and Porsche put more of their focus on it to help it succeed. Little would they know, it would be to no avail.

The outdated car and passed star driver wouldn’t stop the Porsche 962 from continuing to win races throughout 1989. A Miller-High Life team car took overall victory over a Jaguar at the 1989 24 Hours of Daytona. Porsche also denied Mazda a podium with their rotary-powered 767B, which took fifth overall. However, Nissan took victory at the next race in Miami, with the highest finishing 962 sixth overall, behind a Jaguar in second, a Pontiac in third and a Toyota 88C in fourth.

Toyota entered IMSA with legendary car designer and team owner Dan Gurney and his All American Racers (AAR) crew. The 88C was powered by a turbo inline-four that produced an estimated 600hp. It made its debut at Daytona, but retired early with cooling issues. Although Gurney and Toyota designed a differing Eagle HF89, the team concentrated 1989 on the 88C, developing it throughout the season. The development paid off, and with a best of second place at San Antonio and two pole positions at Mid-Ohio and Road Atlanta, the Toyota AAR team started what would become a legacy.

In January of 1989, John Bishop, the brainchild of GTP, began to rethink his priorities after a successful heart surgery in 1987. He was soon approached by the owners of the Tampa Bay Circuit, Mike Cone and Jeff Parker. Bishop quickly sold the series and IMSA’s headquarters were relocated from Connecticut to Tampa Bay. Bishop also stood down as President of IMSA, giving the authority to Mark Raffauf, the Automobile Competition Committee for the United States (ACCUS) representative for IMSA, shaking IMSA up at a time of less than great TV ratings.

Nissan again dominated 1989. At Sebring, the normally short-lived engine propelled Chip Robinson, Geoff Brabham, and Arie Luyendyk to a win by two laps over the second place Jaguar. The Nissan was only denied at Palm Beach, where a Porsche 962 took victory, Portland, where Jaguar’s new XJR-10 took victory by a second and a half over Brabham, Tampa, where an XJR-9 took victory, and Del Mar, where Jaguar capped off the season with a win.

However the ZX-T was becoming dated, and it was time for a replacement. Development work began for a replacement, the NPT-90, but it wasn’t ready by the beginning of the season, forcing Nissan to use the ZX-T until Topeka. Jaguar took victory in the 1990 24 Hours of Daytona, and Nissan once again had issues in the race, but they struck back at Miami, taking their third straight win at the South Florida Street Circuit. They also finished first and second at Sebring, and won next at Road Atlanta and Palm Beach. Toyota, however, had developed the HF89 enough to take victory at Topeka, with the NPT-90 taking eighth, behind two ZX-T’s.

Although Jaguar took victory at Lime Rock Park, it would be the next race at Mid-Ohio that the NPT-90 took its first win by twenty-five seconds over a ZX-T. The Nissan team would then take the NPT back to victory lane at Watkins Glen, before Toyota bit back at Sears Point. Jaguar took another win with their second in a row at Portland, while Nissan would take their final win of the year at Road America. Toyota would win at San Antonio and Del Mar, and Porsche taking a sole win at Tampa with Dyson Racing. Nissan locked up yet another Constructor’s Title and Geoff Brabham another Driver’s Championship, however Toyota and Jaguar became more competitive, and 1991 would signal war.

Over the offseason, Nissan decided that they would try to contend for the race the eluded them for years, the 24 Hours of Daytona. They decided it would be time to bring over the R90CK that they fielded in Group C competition. The Twin-Turbo V8 powered car was more suited to Daytona’s long, banked corners comparative to the developed NPT-90. It was not to be however, as two of the cars failed to finish, and the highest R90CK was placed in only second, eighteen laps behind a Joest Racing Porsche 962C. The NPT-90 would again lose out at Palm Beach, giving the victory to Davy Jones in a Jaguar XJR-10. Wayne Taylor, yes, that Wayne Taylor, would finish second in a privateer Intrepid RM-1 Chevrolet, and Brabham would finish third in a NPT-90.

The NPT-90 had its greatest race at Sebring. It dominated. The Nissan took one and two by a lap over the nearest Porsche, with two 962’s finishing third and fourth. Jaguar, however, had become much better at shorter races, and Raul Boesel took victory in a XJR-10 at the track Nissan had dominated at, Miami. Nissan debuted their NPT-91 at Road Atlanta, but it still was overwhelmed by Jaguar’s car that they debuted, their XJR-16. The NPT-91 took back victory at Topeka and Lime Rock, but the XJR-16 again proved superior in the shorter races, winning at Mid-Ohio with two Intrepids behind it. The privateer Intrepid then took an upset win at the New Orleans 2 Hour race, with Brabham following in second. Toyota and Jaguar took the rest of the victories for the rest of the season, however the Toyota HF90 and XJR-16 were both extremely inconsistent. Nissan took their final Constructor’s Championship and Geoff Brabham his final Driver’s Championship.

Overseas, however, issues were starting to arise with Japan’s economy. After years of economic growth, a bubble had formed. It was only a matter of time before it popped, and it did, massively. Japan’s economy stagnated in Late-1991, and the leading manufacturers in IMSA became drastically effected. Nissan and Toyota immediately pulled back support of the series, leaving development stalled on the NPT-91 and only All American Racers developing, at the least, a beast.

In 1992, Nissan, even after stepping back their support, took victory at the Daytona 24 Hour and the Miami 3 Hour. However, AAR had developed a beast. The Eagle MkIII was born in Late 1991, leading most of its debut race at Laguna Seca Raceway, and winning at Portland and Del Mar. In 1992, it was even better. While Jaguar won at Road Atlanta and Mid-Ohio, Toyota and AAR won the rest of the races, the Constructor’s Championship and the Driver’s Championship. It would be a blessing and a curse.

The Nissan factory team had struggled through 1992. After winning two of the first four races, they lost three chassis at Road Atlanta due to violent tire failures, sending the #84 flipping during practice, the #84T flipping first during the race, followed quickly by the #83. The rest of the year was a struggle. The drivers lost their edge and the chassis weren’t as quick, and with Toyota and Eagle dominating the series, Nissan pulled out all factory support from the IMSA GTP Series.

Mazda, effected heavily by slow sales and a struggling Japanese economy, had to cut costs. Those costs came from the GTP program. Midway through 1992, Mazda pulled out their failing Prototype program. Jaguar soon also saw the writing on the wall, and with Bernie Ecclestone’s strangling of the Group C category, they pulled out of IMSA for 1993. In Late-1992, IMSA announced that the GTP category would be abandoned after 1993. It was the end of an era.

Toyota and AAR went uncontested in 1993, with privateers having pulled out in the era dominated by factory teams, Juan Manuel Fangio II and P.J. Jones took seven and three wins respectively. The last race that included the GTP category took place at Phoenix International Raceway on October 2nd, 1993. GTP was dead, and the greatest era of Prototype racing in the United States had come and gone.