IROC stands for International Race of Champions.  This racing series was formed in 1973 and took the best drivers from many other types of auto racing and lined them against each other in identically prepared cars.  In this first year, they raced Porsche Carreras.  They found the Porsche’s very expensive to build, maintain and race so they needed another car to sponsor the series.  In 1974, Chevrolet signed on with IROC to race this series with Camaros and did so until 1980 and then the Camaro series took a break and returned in late 1984 with a newly designed Camaro to sport.   The Camaro was the featured car for the IROC series from 1974-1980 and from 1984 to 1989.  The cost of sponsoring the IROC series was more than what Chevrolet wanted to spend so they opted not to renew their contract at the end of 1989.  Chevrolet’s licensing to use the IROC label expired at the end of 1989 but the 1990 IROC’s were already being produced.  At 12:00 am, January 1^st., 1990, Chevrolet could no longer sell an IROC-Z.  Hence the IROC-Z was no longer produced after 1990.  The 1990 IROC-Z’s that had been produced in late 1989, before the termination of the license agreement, were able to be sold but after 1989, Chevy officially could no longer produce or sell the IROC-Z. 

The IROC-Z surfaced in 1985 as a $659 option package for the Z/28 until 1987.  From 1988 to the end of the IROC-Z production year, the Z/28 was dropped and the IROC became it’s own model.  This option package included specially designed front and rear suspensions which included Delco front struts, newly designed jounce bumpers, Bilstein gas shocks in the rear, a larger 24 millimeter stabilizer bar, a lower ride height and 16 inch aluminum wheels with P245/50VR16 Goodyear Gatorback tires. 

The L69 motor (190 hp) was the standard option for the IROC in 1985.  Chevy was not satisfied with the performance so they listed the LB9 (305 TPI, 215 hp) as an option which was an alternative to the Cross-Fire fuel-injected V-8’s which Chevy did not keep around very long.  The LB9 was only available with the 4-speed automatic in 1985.  At this time, the newly designed TPI (Tuned Port Injection) system was very sophisticated and very efficient which allowed a jump in performance but did not allow fuel economy to suffer (it actually increased slightly!).  The TPI system used electronic port fuel injection, individual curved intake runners, and a mass air flow sensor which produced excellent torque ratings at 275 ft/lbs @ 3200 RPM’s.  The years following from 1986 to 1989, the LB9 was rated at a mere 190 hp, but torque ratings did increase slightly to 295 ft/lbs.  In 1990, the final farewell of the IROC, Chevy put some serious muscle into the LB9 which rated at 230 hp, only 10 hp less than it’s big brother, the L98 5.7L 350 TPI. 

In 1987 the 5.7L was introduced into the IROC line-up and was rated at 225 hp and was only available with the automatic transmission.  The L98 motor was basically the same motor that was currently being used in the Corvette except the IROC motor had a smaller exhaust to fit in the smaller engine bay, and cast heads instead of aluminum.  The new power plant finally launched the IROC-Z into 14 second ET’s.  Muscle Car Review ran the this new Camaro power plant at 14.88 @ 92 mph.   

Many car magazines at the time had noticed that Camaros and Firebirds were ahead of the competition when it came to handling and overall driving experience due to the upgraded performance modifications.  Quoted from Automobile magazine in the May, 1987 issue, “Slide over from the Firebird to the Formula to the IROC-Z;  the Camaro’s 5.0-liter V-8 feels a touch livelier, a shade sharper.  And the 5.7-liter IROC-Z duly feels like a gutsier beast than the GTA.  You know your in the big mother of the bunch in the large-engined IROC.”