Where do we begin? 1973 sounds like a good round figure … I suppose … how about October 27, 1973. Where? Riverside International Raceway, Riverside, CA of course! This is the date and location of the first, ever, IROC race. The International Race of Champions is a race comprised of top notch drivers from IRL, NASCAR Winston Cup, NASCAR Busch, World of Outlaws … all sorts of racing … to compete in identical cars and try their driving skills at winning the IROC Championship of the season.

What did they drive? Oddly enough, for the 1974 season (IROC I), the car of choice was the Porsche Carerra RSR. Due to costs of running the Porsche, IROC went to the Chevrolet Camaro for the 1975 season (IROC II). IROC stuck with the Camaro until 1990, when the Camaro was replaced by the Dodge Daytona.

Okay, so where does the Camaro IROC-Z tie into this? 1980 was the last season for IROC until it was “reborn” in 1984. For the 1984 season, up until the 1989 season, IROC chose the “newly” designed Camaro Z/28 as their ride. Chevrolet, in turn, had another idea … make a commemorative Camaro model after the IROC series and to celebrate the “rebirth” of the IROC series.

In 1984, Chevrolet introduced the Camaro IROC-Z/28 for the 1985 model year. The IROC-Z was option B4Z on the option sheet and could only be ordered with the Z/28 option package. This new performance icon boasted skid pad numbers within the range of .90 g. The top offering under the hood was the brand new Tuned Port Injection (TPI) 305 cubic inch V-8, which boasted 215 horsepower and 275 ft/lbs of torque, the most powerful 305 automatic ever offered in an IROC.

The eye appeal was astounding and separated itself from the Z/28 model Camaro. The IROC-Z/28 came with a redesigned front fascia with a more rounded appearance and a deeper chin spoiler with lower ground effects. The new fake hood louvers were introduced on the Z/28 and IROC-Z/28. (To find out more specific highlights and differences of your model year IROC-Z, visit IROCZONE .com’s Spotter’s Guide section).

Food for Thought

The 1990 IROC-Z

If IROC went to the Dodge Daytona for the 1990 IROC Season, why were there Camaro IROC-Z’s still built in 1990? The simple answer: there weren’t. All 1990 IROC-Z’s were built up until the end of 1989 for the 1990 model year. When Dodge took over sponsorship for the IROC series, production of the IROC-Z Camaro ceased. This is why there were so few 1990 IROC-Z’s. All 1990 IROC-Z Camaros were built in 1989, not 1990.

Where’s the Power?

We’ll be straight up and admit, IROC-Z/28 Camaros were definitely not the most powerful muscle car GM ever built. So what happened? How could GM release a 450HP Chevelle in 1970, a 325HP Camaro in 2002, but the best they could do for the top of the line IROC-Z in 1988 was 230HP? Well, GM wasn’t the only automaker faced with this unique dilemma in the 1980′s. The 1980′s was probably the worst era for performance cars. The auto industry as a whole, was facing the music with new buzz words like ‘efficiency’ and ‘fuel economy.’ Technology wasn’t as great back then as it is now so putting together a powerful, yet efficient V-8 power plant was more difficult than we might think. To top it all off, in the late 1970′s, when C.A.F.E. standards were federally mandated, it looked like the V-8 would not survive into the mid-80′s. The struggle is felt even today, but with newer technology and breakthroughs, auto makers keep increasing horsepower, and keeping economy at it’s peak. Don’t get us wrong, the IROC-Z isn’t any old car you can push around. They still produce gobs of torque and some suggest that GM actually “underrated” the horsepower numbers. For those of us IROC-Z owners, let’s be thankful of our power plants, they were the best that could be offered at the time of the mid-80′s “crunch” and still can pack a punch.

  • Year 1988 2002
  • Model Camaro IROC-Z Camaro Z/28
  • Engine 5.7L V-8 5.7L V-8
  • Power 230HP @ 4400RPM 325 @ 5200RPM
  • Economy 16 City/20 Highway 19 City/28 Highway

Simple chart showing the difference in power versus economy in 15 years

Year by year history breakdown of the IROC-Z Camaro.

Source: IROC-Z Homepage


The IROC (International Race Of Champions) began using the Camaro as the official vehicle. To commemorate this, Chevy made an IROC model for the Camaro. The IROC-Z was option B4Z on the option sheet and could only be ordered with the Z28 option package. The ride height was lower than a standard Z28, and featured performance-calibrated front struts and springs, Bilstein rear shocks and 16 inch aluminum wheels with Goodyear Eagle 245/50/16 tires. This new performance icon boasted skidpad numbers within the range of .90 g. The top offering under the hood was the brand new TPI 305 which boasted 215 horsepower and 275 ft/lbs of torque. This was the most powerful 305 automatic ever offered in the IROC. The 190 horsepower HO 4bbl 305 and the standard output 155 horse LG4 were the other available motors.

The IROC also came with a redesigned front fascia with a more rounded appearance and a deeper chin spoiler with lower ground effects. The new fake hood louvers were introduced on the Z28 and IROC. The IROC was available in Yellow, Bright Blue Metallic, Black, Silver Metalic and Red.


In 1986, the IROC received slightly different engine packages. The 86 IROC is the armpit of the entire run. The 305 block in 1986 now had a one piece rear main seal. The TPI 305 was the lucky recipient of the LG4 camshaft, and the result was a drop of 25 horses and almost a half second longer run to 60mph. Chevrolet did allow 50 IROCs out the door with the 220hp L98 350. Beware when somebody sells an 86 as a stock 350. CHECK THE VIN for accuracy. Chevy also let an undisclosed number of these cars out with the T5 five speed transmission as part of the 1LE racing option that also included air conditioning delete, radio delete, as well as the deletion of all power accessories. The 1LE option was not available with T-tops, but did come with specially calibrated springs, shocks and sway bars.

Visually, not too much changed on the 86 IROC. The government mandated 3rd brake light found its way to the top of the rear hatch near the roof line. Curiously, rear window louvers became a factory option this year. Some of the 86 IROCs came with the new 140mph speedometer. 86 was also the first year for the base coat/clear coat paint system as standard equipment.


1987 brought about only minor changes to the IROC. The motors now had the new center bolt style heads and manifolds had a revised bolt hole angle to accommodate the different heads. The motors also made the switch to hydraulic roller camshafts. This gave a 3.5% increase in gas mileage, and an extra 5 horsepower. The TPI 350 was now widely available, but only with the 700R4 automatic.

Visually, the 87 is identical to the 86 model, except that the third brake light moved from up on the rear hatch, to down in the rear spoiler.


1988 brought about some welcome changes in the horsepower department, as well as a somewhat revised exterior scheme. The Z28 was discontinued, and the IROC was now its own model. For the first time in the history of the Camaro, no carbureted Camaros were available. All motors offered fuel injection of some sort. The base IROC motor had the TBI injection that was very similar to what was found on the trucks. A new camshaft finally found its way into the 305 TPI and boosted horsepower to 195 horse in the auto, and a stout 220 horse when backed with the T5. The 350 also got a small horsepower boost to 225 horse. All of the V8s starting in 88 had “guided rocker arms” that featured a stamped-in lip on each side of the pad that contacts the valve stem.

The exterior of the IROCs received a mild update for 88. The most noticeable difference is that the wheels have been slightly changed. Instead of one line through the center of each spoke, there were now two lines, and the center area was a little different. Here’s an interesting tidbit: for the first time, the 16″ wheel was an option on the IROC. The car came standard with a 15″ version. Along with that, the IROC-Z decal was a little smaller and moved to the rear of the door instead of the front. The stripe along the ground effects line now had the black line above the silver. The silver Z-28 badges on the exterior have been replaced with orange IROC-Z logos.


1989 brought about some nice horsepower increases. The TPI 305 5 speed jumped to 230 horse if the dual catalytic converters were ordered, and with dual cats, the L98 350 jumped to 240 horse, with a staggering 345 ft/lbs of torque! The TPI systems changed slightly. For the first time, the 9th cold start injector was no longer used.

Visually, nothing changed from the 1988 model.


This is the first year the 1LE high performance option became widely known. The 1LE featured 4 wheel disk brakes, a 3.42 posi rear end, an aluminum drive shaft, large 12″ front rotors, aluminum calipers, engine oil cooler, larger anti-roll bars and gas tank baffles. There were also numerous spring rates available. The package could only be ordered without air conditioning or fog lamps. 1990 also marked the year the the TPI systems changed from the Mass airflow system to the Speed density system. These differences are explained in the TPI tech section. The Speed density system allowed an extra 5 horsepower from the 350, upping the ante to 245.

Visually, the exterior of the 90 IROCs once again did not change, but looking through the windows will show that they now had a driver side air bag as well as revised instrument cluster.

IROC History

These are some brief history spots we’ve noted through the entire history of IROC. We also added tidbits of the cars they used throughout the years as well. We’ve left out some years and hope to add a bit more later on down the road, but at least it’s a good start. For complete details of the history of IROC Racing, look no further than !
IROC I – 1974 Season

Porsche Carerra RSR

1974 Season begins. First IROC race (IROC I) took place at Riverside International Raceway, Riverside, CA on October 27, 1973. This track is a 2.54 mile road course of which the race consisted of 30 laps and a total of 76.2 miles of total racing. Average speed was 101.3 MPH and the winner was Mark Donohue from Reading, PA, who led all 30 laps in his #1 IROC racer. The car was the Porsche Carerra RSR. The last race of the IROC I (1974) season took place on February 14, 1974, proving Mark Donohue the winner once again. Mark Donohue finished the season #1, winning 3 out of the 4 races. He lost the 2nd race (in the series of 4) due to a problem with the throttle linkage, which sent him out of the race on the 7th lap. Donohue later retired as an active driver, only to return to competition later in 1974. On a sad note, Donohue was killed the following season after a Formula One practice accident.
IROC II – 1975 Season

Chevrolet Camaro

First race of 4 in IROC II took place at Michigan International Speedway, Brooklyn, MI on September 14, 1974. This track is a 2 mile oval track of which the race consisted of 50 laps, totalling 100 miles of total racing. This season marks the first in which the cars were replaced with Chevrolet Camaros. The Chevrolet Camaro was used up until 1990 when the choice was made to replace the Camaros with Dodge Daytonas. Bobby Unser took the season, winning 2 out of the 4 races as well as coming in second on the third race.
IROC III – 1976 Season

Chevrolet Camaro

The third season started out, once again, at Michigan International Speedway on September 13, 1975. A. J. Foyt won his first IROC title without winning a single race in the season. This was the first time the series champion was determined by total points of the four events.
IROC III – 1977 Season

Chevrolet Camaro

Yet, another season starting out at Michigan International Speedway on September 18, 1976. A. J. Foyt won his second consecutive IROC title without winning a single race in the season.
IROC VII – 1980 Season

Chevrolet Camaro

June 16, 1979 started the 7th season of IROC racing. Since the first season, several changes have taken place beginning in the second season where the car was changed to the Chevrolet Camaro. The introduction of the use of oval tracks began in the second season as well, starting with the Michigan International Speedway. In the third season, the concept of total points to declare the champion was born. The 1980 season marked the spot where IROC racing was deamed for history for this was the last season … or at least until 1984.

IROC VIII – 1984 Season

Chevrolet Camaro Z28

IROC Racing was “reborn” on June 16, 1984 at Michigan International Speedway. Ending on August 11, 1984 again, at Michigan International Speedway leaving the NASCAR driver, Cale Yarborough the IROC 8 champion. The third race at Talladega Superspeedway proved an average speed just a hair over 179 MPH, the highest thus far. Average speeds throughout the different years prove to be fairly consistent per track. 1984 marked the first season in which the third generation style Camaro Z28 was used, sparking GM to draft together a commemorative production model for the following year.
IROC IX – 1985 Season

Chevrolet Camaro Z28

For the first time in IROC history, the series champion was determined in a tiebreaker after the last race. Under IROC rules, Harry Grant was declared champion because he finished higher in the final race. Average speed climbed up to just over 182 MPH at the Talladega Superspeedway for the first race that took place on Februrary 15, 1985. This year also marked the first model year of the commemorative production IROC-Z Camaro as an additional model to the existing line.
IROC XIV – 1990 Season

Dodge Daytona

IROC began a new era in its history with the introduction of the Dodge Daytona as the vechile of choice for 1990. With this decision, the IROC-Z production model Camaro was ceased early in the year due to the loss of the licensing for use of the name. On May 5, 1990, a new IROC record was achieved at the Talladega Superspeedway with an average speed of 188.055 MPH in the first race of which Dale Earnhardt took the checkered flag as well as the 1990 IROC season championship.
IROC XVI – 1992 Season

Dodge Daytona

Race 2 of the season hightened the average speed once again at Talladega Superspeedway, boasting a quick 191.722 MPH. Ricky Rudd took the IROC 16 championship with Dale Earnhardt taking second overall. For the 1992 model year, Dodge release it’s own version of the production, front-wheel-drive, IROC Daytona.
IROC XVII – 1993 Season

Dodge Daytona

The last season for the short-lived Dodge Daytona cars. Davey Allison won the series, but unfortunately, he died prior to the last race. Terry Labonte stepped in to replace the late Davey Allison of which Labonte’s points went to Davey Allison’s total for the champtionship. 1993 marks the last year for the even shorter lived production model Dodge Daytona IROC. Perhaps the public wasn’t interested enough to justify further production.
IROC XVIII – 1994 Season

Dodge Avenger

The Dodge Daytona was replaced with a new Dodge Avenger sports coupe. The Dodge Avenger was used only two years, only to be replaced by the Pontiac Firebird Trans Am in 1996. Mark Martin took the IROC 18 championship with Al Unser Jr, Rusty Wallace and Dale Earnhardt coming into a close second, third and forth. All three were tied in points and the placing was determined by their positions in the last race.
IROC XX – 1996 Season

Pontiac Firebird Trans Am

Mark Martin took back the championship once again, coming back from Dale Earnhardt’s defeat the season before. The first year for the Pontiac Firebird Trans Am to be used as the IROC car of choice. There is no discussion or planning that we know of, that Pontiac (GM) will ever release an IROC model of the Firebird Trans Am. Many feel that the IROC name associates well with the Camaro from the 1985 to 1990 era, that there should be no intention of disturbing that with an IROC Firebird.
IROC XXIII – 1999 Season

Pontiac Firebird Trans Am

Mark Martin’s continuous championship winning streak is ended. Winning three consecutive seasons from 1996 to 1998, he has squeezed to second place for season with a margin of 1 point.
IROC XXV – 2001 Season

Pontiac Firebird Trans Am

After Race 1 of the 2001 IROC season, Dale Earnhardt lost his life during the last corner, of the last lap, in the Daytona 500 on February 18th, 2001. Not only did NASCAR loose one of its best drivers … so did the IROC series. The rest of the season played out with the 11 remaining competitors, not replacing Dale Earnhardt’s spot. Bobby Labonte emerged as the 2001 IROC champion, clinching a 1st place finish by .324 seconds over 2nd place finisher, Tony Stewart, in the final IROC race of the season. Bobby Labonte was driving the infamous #1 Black Firebird.

Find out more information and detail about the history of IROC Racing plus current events and much more at the home of IROC Racing, IROCRACING.COM, International Race of Champions