The IROC-Z replaced the Camaro Z28 from 1985 through 1990. RPO B4Z. Visual signature: deep-cut front fascia with fog lamps, lower body-side ground effects, IROC-Z badging on the doors and rear panel, gold cross-lace 16-inch wheels (or the 'salad shooter' five-spoke). Mechanical: LB9 305 TPI standard, L98 350 TPI optional from 1987, T-5 manual or 700-R4 automatic.
Designer — IROC-Z is a 1985 mid-cycle restyle of Jerry Palmer's third-generation Camaro body. Ground effects, the lower fascia, and the IROC-specific wheels are addenda to Palmer's original Chevrolet Studio shape rather than a separate body design. The Trans Am side of the F-body received its own restyle over the same period under Pontiac No. 2 studio chief John Schinella.
Chevrolet ended the IROC partnership at end of 1990 model year and reverted to the Z28 designation for 1991–92. Build dates and SPID option-block content disambiguate IROC-Z from Z28 in transition cars.