1985-87 Chevrolet Camaro Iroc-Z

Nineteen-eighty-two marked the transformation for Chevrolet's four-seat performance car. Jerry Palmer was the chief stylist for the third-generation Camaro and still calls the third generation a fabulous car. The entire design and engineering team worked together to bring about what was the best handling GM car to date. At the outset, the engineers gave the new car a 101-inch wheelbase, 187.8-inch overall length, 72-inch width and 49.8-inch height. "Chuck (Jordan) had several requirements for us when we set out to do this car: He wanted a 62-degree sloped windshield, which at the time was the steepest we'd ever done, and he wanted a one-piece side glass. Chuck would not tolerate a warmed-over second-generation car," says Palmer, now 62 and retired from his duties at GM. "He drove us to reach out and really design a new and exciting car. It was a simple statement and had a great stance. Just parked, it looked like it was ready to launch, a real street fighter."

Fred Schaafsma worked with Palmer on the third-generation car and remembers that it was the most intense project he ever worked on while at GM, before retiring three years ago. "Our focus was on handling. Not just cornering, but response and getting the body structure right. We did not just want great cornering but make the car responsive as well. We did a lot of work on the steering. Remember, we did not have rack-and-pinion steering yet and did a lot of work on the rotary valve inside the recirculating ball steering and control response tests, which were very important," he said. Schaafsma paid particular attention to the strut design, measuring hydraulic curves and stiffness, the strength of brake knuckles and spent many hours with Goodyear engineers for tire development. "Most of this work went toward the Z28, but we also wanted crisp handling on the other Camaros, such as the Berlinetta." Schaafsma also notes that many hours were devoted to ergonomics, such as shifter placement, how would it feel to the driver.

Engine compartment busy in 1987; this one remains factory correct.

That crisp handling and emphasis on ergonomics carried all the way through to 1985, when Chevrolet debuted the IROC-Z. The same year, Chevrolet had introduced its new Tuned Port Injection, an alternative method of injection, replacing the basic Throttle Body Injection.

It probably goes without saying that "IROC" is an acronym for the International Race of Champions, a series of annual events in which drivers from all forms of motorsports compete against one another in identically prepared cars. IROC drivers had driven race-prepared Camaros since 1974. The IROC-Z was not a separate model, but was an option on the Z28, code B4Z with a cost of $695. In essence, it was a suspension package built around the 16 x 8-inch wheels and massive Goodyear tires. The IROC-Z also had louvered inserts, bolder ground effects and spoilers than a base Z28.

A true handler, the IROC-Z came with special front struts, springs and jounce bumpers, Delco-Bilstein rear shocks, special rear springs, anti-roll bar, higher effort steering, increased caster wheel alignment, front frame rail reinforcement, 16 x 8-inch aluminum wheels, Goodyear Eagle P245/50VR16 tires and special graphics. The entire package resulted in a Camaro that could pull 0.92 Gs on the skid pad and seven second 0-to-60 mph times in stock trim.

On the surface, the IROC may have looked unchanged throughout its entire run, but significant changes were taking place under the skin. Therefore, our Buyer's Guide will concentrate on the 1985 to 1987 models.

ENGINES

In 1985, the IROC's first year, the Z28's base 190hp L69 305 V-8 could still be ordered with the IROC-Z package, but was only available with a five-speed manual transmission. The 190hp engine had a bore and stroke of 3.74 inches x 3.48 inches, compression ratio of 9.5:1 and 240-lbs.ft. of torque. It breathed with a Rochester E4ME four-barrel carburetor and carried a G engine code.

Camaro engineers raided the Corvette parts bin and swiped the new Tuned Port Injection for the IROC's 305-cu.in. V-8, which made 215hp that first year. The optional TPI 305-cu.in. engine had 275-lbs.ft. of torque, with the same compression ratio as the carbureted 305. An "F" in the VIN denotes this engine. The TPI 305 could only be ordered with a four-speed automatic transmission.

In 1986, emissions regulations and a resulting revised camshaft profile resulted in a net loss of 25hp from the TPI engine. The L69 still could be ordered, but GM quietly killed that very early in the model.

The big news came in 1987, when the Camaro finally got the 350-cu.in. TPI V-8, even though records show some very late IROCs had this engine. This brute offered 220hp. However, while the new B2L engine looked identical to the Corvette's L98, it lacked the four-bolt main bearing caps and further cost cutting eliminated the Corvette's aluminum heads.

GM was prevented from designing more efficient air filtration and exhaust systems without costly emission recertification tests, so the B2L breathed through the LB9's intake and exhaust systems. Despite this, the B2L lost only 15hp to the Corvette, but set a buyer back $1,045, making it the most costly engine for a Camaro since the ZL-1's $4,000 price in 1969.

TRANSMISSIONS

There were two transmissions available for the IROC: A T-5 five-speed manual and a four-speed automatic, with the five-speed manual being standard on all 305-cu.in.-engined IROC-Zs. The four-speed overdrive automatic, a 700R4, was beefed up in late 1986 to address breakage and became an exceptional transmission. The improved 700R4 had changes to the main and auxiliary valve bodies and other components were stronger.

Additionally, the newer version had an accumulator to regulate the engagement of the forward clutch, so the shift into "D" would be smoother. Engineers also smoothed out the reverse clutch engagement so it would be stronger in "abusive" situations. The newer 700R4 also had larger splines on the input and output shafts from 27 to 30 and a 10-vane pump replaced the 7-vane pump, which resulted in more pressure, leading to firmer, quicker shifts and longer life.

The 350 V-8 required the 700R4 as the T-5 manual could not handle this engine's torque.

DIFFERENTIALS

Third-generation Camaros had some rear-end noise problems, which were cured when Chevrolet revised the torque-assembly specifications. But growling from a limited-slip differential can also be attributed to poor maintenance. Limited-slip units should have their fluid changed, including new GM additive, about every 15,000 miles. Fortunately, if the owner neglected the posi unit, a fluid change with additive normally takes care of the howling.

The mid-1980s saw a 7.68-inch 10-bolt unit installed; an Australian-built 9-bolt rear end was also available. The Aussie version was considered marginally stronger than the 10-bolt version, but has been known to break and was quite expensive to repair, so many have swapped in a 10-bolt unit. The Australian-built rear end debuted in 1987, and could be ordered with the IROC when the 350 V-8 was ordered.

SUSPENSION & BRAKES

While the TPI 350 was the big news, the IROC-Z really proved its mettle in the handling department, regardless of which engine the buyer ultimately selected. When the IROC-Z burst onto the scene in 1985 it was advertised as "the Camaro that thinks it's a Corvette." The idea behind the IROC centered around ways to take a plain Z28 and transform it into a true high-performance/handling Camaro that anyone could own without having to hold an SCCA license.

The upgrades to the suspension system made an IROC sit a half-inch lower than a standard Z28 and gave it skid pad numbers in the .90g range. The front used a modified MacPherson strut, meaning the coils did not wrap around the struts, but rather stood between a single lower A-arm and the crossmember. These gas-charged strut cartridges were made by Bilstein and were specific to the IROC. Additionally, there were lower ball joints and a front anti-roll bar. The Z28 had recirculating-ball power steering with a 12.7:1 ratio, plus limited boost to give the driver more road feel.

With all the handling improvements, the IROC-Z still soldiered on with a live rear axle. But the rear suspension had a new torque arm on the rear axle and transmission, which saved space and weight. The balance of the IROC-Z package included stiffer coil springs, gas-charged tubular hydraulic shocks, a lateral diagonal track bar and rear anti-roll bar. The brake setup on IROCs consisted of front and rear disc brakes because when ordering J65 four-wheel discs, one must have ordered the IROC option. To further complicate things, when ordering the J65 brake package, one also had to check off the G92 performance axle or 350 TPI engine. The rotors used on this system in these three years of production were 10.5 inches front and rear.

WHEELS & TIRES

The IROC-Z is one of the first American cars to wear 16-inch wheels as standard equipment. The 16 x 8-inch aluminum wheels were wrapped in massive Goodyear Eagle GT P245/50VR16 blackwall tires. The numbers don't sound big today when you can purchase a Dodge Ram pickup truck with 20-inch wheels, but they were huge in the mid-1980s.

The Goodyear Eagles tend to wear on the edges if not rotated at prescribed intervals, and even more importantly, if they aren't inflated to proper pressure. These tires are costly if you can find originals, but an exact replacement is no longer available. The correct size is available from Goodyear in a GS-C style. When looking at a third-generation Camaro, check the tires carefully. One thing to check is the front and rear wheels on a IROC, because they have different offsets, and the rear wheels are different than the fronts, so tires cannot be rotated front-to-back. In 1987, this was the last year GM used the "single indented" 16-inch wheel.

CHASSIS

All IROC-Zs, like their lesser brethren, use a front K-member or cradle bolted to a unibody. When IROC-Zs were on the assembly line, the engines were loaded into the car from underneath. Engineer Dan Beane was directly responsible for the front bolt-on crossmember.

The final design included long, tubular spacers inside the crossmember and six long bolts instead of four short ones. The inner fender area and core support are integrated with the car's body itself. A caveat of this construction is you cannot unbolt the front end and replace sheet metal if the under structure is crunched.

The chassis is susceptible to rust, but GM used some of the best anti-corrosion methods available at the time like zincrometal, which is sheet steel, which had four coatings of zinc-rich primer baked onto its surface. Rust often starts on the inside and works its way out. This process guarded against that. Third-generation cars also had extensive use of galvanized steel.

BODY

Rust in the toeboards, which was a disastrous problem in second-generation Camaros, was put on hold with extra paint and special sealers like Plastisol and hot aluminized waxes. Outer body panels used chip resistant Plastisol. Previous T-top equipped cars had water leaks, but engineers developed a new sealing material in March 1984, and it has proven to be an effective fix. Most times when water did leak in through the roof, it ran down the side glass and into the door itself, then out the drain holes, if they weren't clogged.

Paint on these cars is better if your car came from the Norwood, Ohio, factory rather than the Van Nuys, California, plant for one big reason: more strict California air pollution laws. Specifically, Van Nuys workers had to use water-based enamels in contrast to solvent-based paints in Ohio. In 1987, the year Norwood closed, the workers were putting out some of the highest quality paint jobs in the world with a new Turbo Bell paint system, which electrically charged paint to the car bodies with virtually no overspray. Norwood cars have an "N" as the 11th digit of the VIN; a Van Nuys-built Camaro has an "L" instead.

While not the first frameless glass on an American car, it was the first ever to feature a "reverse bend" rear glass meaning it was curved and had an "S" curve and was both positive and negative in the crown of the glass. "It was a major deal and I remember LOF and PPG duking it out for the contract. I think LOF won out, but PPG came along later and did some of those windows for us," Jerry Palmer notes.

INTERIOR

The interior was designed by engineers George R. Angersbach and William D. Scott. They wanted a "driver-oriented" interior, paying attention to steering and shifter position. They also wanted all instruments at the driver's fingertips, where they could be seen at all times. The new interior made rear seat passengers more comfortable than previous Camaros, where they found their knees into their chest. In the rear, the new car had two more inches of shoulder room and more knee room.

The new seats, frames made by Lear-Siegler, were comfortable, due in part to thigh support, lateral bolster adjustment, lumbar adjustment, adjustable headrests and seatback angle. Due to availability, an optional Conteur driver's seat came one per Z28. Drivers more than 6 feet 4 inches tall report the cars are quite comfortable, even on long trips. A console came standard in all Camaros and housed the shifter, power window and rear hatch controls, parking brake lever, quartz clock and rear-seat ashtray. Door panels were soft-padded vinyl and could be ordered with optional carpeted cloth on the lower half.

REPRODUCTION PARTS

Although these cars are now 20 years old, the reproduction market is lacking, says third-generation Z28 expert Mike Maciolek. Most available parts are coming from GM, but many have been discontinued. Hopefully, the reproduction aftermarket will kick in and produce needed components.

PERFORMANCE PARTS

While first- and second-generation Camaros enjoy a clogged aftermarket, IROC-Zs are coming into their own with everything available from high-performance air cleaners to ring and pinion sets.

Even though these are among the best handling and braking cars built in the mid-1980s, there are upgrades available from high-performance slotted brake rotor kits, aluminum calipers with huge pistons and high-performance brake pads. However, unlike old carbureted versions, any fuel-injected car must be modified with care. Maciolek recommends understanding the TPI or TBI units before you jump headfirst into them. The weak T-5 can be replaced with a T-56 transmission, and the rear axles are weak. If you are going to race the car, you can buy a pre-made Ford 9-inch, which is very stout or Chevrolet 12-bolt rear for a third-generation car. Expensive, but they won't break.

CHASSIS UPGRADES

Maciolek says the durability of an IROC chassis is marginal when more power is introduced. But there are many parts made today by companies such as Global West and Performance Suspension Technology, which can improve the handling of your IROC-Z.

Experts note that the single biggest improvement one can do to these cars is add sub-frame connectors. You'll want to buy the type that are welded in rather than bolted in, because there is tremendous stress that can cause the bolt holes to become larger, rendering the sub-frame connectors less effective over time. Global West makes some stronger pieces for this upgrade. The downside is they weigh about 20 pounds.

Another worthwhile upgrade are strut tower braces. Weighing just six pounds, these reduce flex. Add to that aftermarket tie-rod sleeves at $40 and you'll have stronger, adjustable pieces.

Global West also makes a steering brace, which mounts under the front anti-roll bar, yet retains stock bushing bolts and will lock the bottom of the front K cradle and keep it from moving side to side.