only start in an IRL-sanctioned race. When the IRL switched to normally-aspirated engines for 1997, the 265s were no longer permitted in the IRL and the Indy 500, and from that point on raced in the CART series exclusively. F1 debut In 1991 Ilmor entered Formula 1 with a V10 engine as exclusive supplier to the ambitious Leyton House team (formerly March). After some troubles Leyton House returned to racing as March again in 1992, still using Ilmor engines. Ilmor also supplied engines to the Tyrrell team, starting from 1992. Powered by the Ilmor V10, Tyrrell scored 8 points through Andrea de Cesaris and March another 3 through Karl Wendlinger. Sauber Ilmor were gaining a reasonable reputation in F1, and so the Sauber sportscar team and Mercedes-Benz, who were planning their Formula One entry together, signed a deal with Ilmor after scrapping plans for a Mercedes engine. In order to protect their image, Mercedes took on an observational role in the project and the cars had "Concept by Mercedes-Benz" written in the engine cover. After scoring 12 points in 1993, Mercedes entered officially in 1994 using an updated version of the 1993 engine, and now "Powered by Mercedes-Benz" was seen on the Sauber engine-cover. The same year Mercedes-Benz acquired Chevrolet's 25% share of Ilmor. In 1994 Ilmor also supplied the new Pacific GP team of Keith Wiggins with the old 1993 spec customer engines. In 32 attempts, the Pacific cars qualified seven times. After Pacific GP Lotus lost its Ilmor customer supply deal to Ford Zetec in 1995, Ilmor decided to reposition its Formula One involvement. Racing in the United States The 265D V8s ran the entire 1994 Indy Car season badged as "Ilmor Indy V8", with Team Penske headlining the program, which included free engines. In 1994, Ilmor produced the Mercedes-Benz 500I engine for Team Penske (although work on this started long before the Mercedes takeover as a private project between Ilmor and Penske). The 500I exploited a loophole in the engine rules at the Indianapolis 500 (which was run under slightly different rules to other CART races). Originally stock-block engines based on production units, fitted with two pushrod and rocker arm actuated valves per cylinder, were permitted to run at increased cubic capacity (3.43 litres vs 2.65 litres) and significantly greater turbo boost than the pure racing engines. For several years Buick V6 units had been extremely fast