There was some acrimony in their split from Cosworth, their former employer claiming that the Ilmor engine was little different from their planned modifications to the DFX.

The Ilmor 265-A, badged initially as the Ilmor-Chevrolet Indy V-8, debuted at the 1986 Indianapolis 500 with Team Penske driver Al Unser.

Mario Andretti, driving for Newman/Haas, won at Long Beach, the engine's first Indy car victory.

Emerson Fittipaldi drove a "Chevy-B" to 4th place in points, but both he and Mears dropped out of that year's Indy 500 due to crashes.

Some backmarker teams continued to utilize the "A" and "B" engines during the 1993 season, but neither the "A" nor the "B" would win another Indy car race.