One of four Interscope chassis built for the first Porsche Indycar Project! The sole surviving Porsche “940” Indycar! Original chassis, original engine, original gearbox! Completely restored to running condition – finished in 2020!
By 1979 the Porsche Motorsport Team had already been very successful in the Sportscar World Championship for 20 years after they had first won the Targa Florio in a Porsche 718 RSK in 1959. Numerous victories at the 24h of Le Mans, 24h of Daytona, 12h of Sebring and other major racing events followed. At that point the management of Porsche decided to increase their racing activities in North America by trying to win the most important racing event in the US – the 500 miles of Indianapolis.
With three victories at Le Mans in works entered Porsche 936s in 1976 and 1977 and a Kremer Racing entered Porsche 935 in 1979, Porsche had a sufficiently powerful and reliable engine for the project. Instead of the dual turbocharged layout of the 935, the USAC regulations for Indianapolis however only allowed a single turbocharger unit and demanded that the engines had to be run with pure Methanol.
Main personnel to be tasked with the project were Manfred Jantke as project leader and Valentin Schäffer as leading drivetrain engineer. While Jantke had been Head of Porsche Sports and PR since 1972 and already been responsible for all three Le Mans victories, Valentin Schäffer worked for Porsche’s race engine department already since 1955 and was the executing engineer of all Porsche race engine projects designed by Hans Mezger.
Manfred Jantke introduced the Indianapolis project to the public for the first time at the Hilton Hotel in Stuttgart in December 1979 together with their chosen driver – Hawaiian Danny Ongais. The work on the project had already begun in January of the same year with a first visit of Valentin Schäffer at the designated project partner and chassis manufacturer Interscope.
Interscope Racing was a successful team in the USAC series since the mid 1970s and even competed in a couple of Formula 1 World Championship races in 1977. At the presentation in Stuttgart Porsche still showed a development and marketing car based on an outdated Parnelli Indycar chassis, since the development of a completely new ground-effect car, designed by Roman Slobodinski, was ongoing at the Interscope workshop in Santa Ana, California. Slobodinski had already been head of design for the Dan Guerney AAR Eagle racecars.
By July 1979 the team had managed to mate the adapted engine to the newly developed Interscope aluminium-monocoque, which needed a subframe to support the non-self-supporting engine unit. To further comply with the USAC regulations the displacement of the engine was reduced in size to 2,649.5 cc, the car received a Porsche four-speed gearbox with dog engagement and the boost pressure was set at 54 inches of mercury, which was in between the allowed boost pressures of four- and eight-cylinder engines of the 1979 USAC regulations.
The first successful test of the new car was held on the Ontario Motorspeedway in mid-October 1979. Subsequently the management of the Porsche AG decided to strengthen the cooperation with Interscope Racing and participate at the Indianapolis 500 and the USAC series in the newly developed Interscope Porsche IP-1 at the earliest possible date.
Although Porsche’s assumption that the boost pressure for six-cylinder engines would be set in between the boost pressure of four- and eight-cylinder engines in the official regulations, the USAC struggled to finally make a decision. Rumours spread amongst the well-established Indycar teams that Porsche’s new Indianapolis contender was two seconds quicker at the Ontario Speedway than anyone before. When the team conducted further tests on the track, the Porsche engineers reported that at least one helicopter was watching and supposedly stopping lap times.
Nowadays the opinion has taken root that this caused the USAC to decide on setting the boost pressure at only 48 inches of mercury for six-cylinder engines – the same as for eight-cylinder engines. This in turn meant, that the 935/72 Porsche engine in current stage of development would have produced a nominal power that would have left the Porsche team hopelessly uncompetitive. A completely revised short-stroke engine design was necessary.
Although Interscope Racing obtained an official approval by the Porsche team during the 1980 24h of Le Mans to continue the development on the car and the new engine, the management of the Porsche AG cancelled all further work in September 1980 on Porsche’s first attempt to compete at the Indianapolis 500. At least two of the newly constructed chassis were reused running for the Interscope team with Cosworth engines the following years.
The car KW is offering was found at Tom McBurnie’s workshop in Santee, California in 2008 by the current owner. The car was in need of a full restoration, did not have an original engine but was still in the Porsche-spec-state and obviously not one of the cars, that was reused by Interscope in 1981. It took several years until the owner found a possibility to acquire one of the ten original Porsche 935/72 Indycar engines and start the full rebuild.
Since official documents and build sheets were unobtainable, the work took another few years to bring the car back to as-close-as-original specifications and fully running order. The restoration was just recently finished and the car should have been shown at one of the great events like the Goodwood Festival of Speed if not for the current special situation. This Interscope Porsche Indycar is an important part of Porsche’s North American racing history and very likely the only car to have survived in original spec.