IROC Camaro Z28 (A champ in its own right)

JT  Mar 12 2007 - 2:41pm   



IROC Camaro Z28 (A champ in its own right)


Car and Driver October 1984



Everyone likes a good commemoration.  When Neil Armstrong first walked on the moon, the government issued postage stamps to celebrate the occasion.   Last summer, coin collectors got their shot at an edition of Olympic gold and silver pieces.  And half the t-shirts in America honor the memory of one thing or another.


It's the same in the car business.  Whenever a manufacturer paces the race at Indy, it's a sure bet that pace-car replicas will appear in the dealerships.  Special anniversary models are also minted at regular intervals.


It is therefore no surprise to find that there's an IROC Camaro Z28 for 1985.  This model commemorates the recently revived International Race of Champions, which is contested exclusively in-you guessed it-Z28 Camaros.


This new Camaro takes its name, at least, from a truly important event in motorsports.  The IROC series, which was inaugurated in 1973, pits several of the world's top international racing stars against one another on road courses and oval tracks.  Truth to be known, a garden-variety Z28 has about as much in common with a tube-frame IROC race car as it does with a cruise missle.  The similarities stop with the bodywork, which would naturally lead you to assume that the civilian model is just one more dealer-inspired paint-and-stripes sales hype.


Nothing, however, could be farther from the truth.  The 1985 IROC Camaro Z28 isn't just a simple commemorative model; its a champ in its own right.   After a couple of days in the saddle of two pre-production IROC-Z prototypes, we're prepared to say that this latest Camaro promises to be something special indeed.


Part of the reason the IROC-Z is a genuine step forward is that it's one of those rare models conceived deep within the engineering department rather than at the executive level.  The IROC-Z is the product of some determined tinkering by a handful of Camaro development engineers.  Although they had already improved the 1984 model sinificantly, this same group took it upon themselves to go further.   "This is really the culmination of the Z28-what we would have liked it to be from the beginnning," says Camaro engineer Phil Leistra.


Unfortunately, some indecisiveness on the part of the product planners makes actually buying the engineers' ultimate Z28 more difficult than it need be.   Basically, you must take it upon yourself to make all the right moves on the order form.  it's up to you to specify the right engine, gearbox, and options-or to be careful that the IROC-Z the dealer is trying to sell you off his lot has all the proper stuff.


What the IROC-Z package does contain is everything needed to elevate the standard Z28's road manners to a much higher plane.  The most obvious and important change is better rubber.  The standard Z28's P215/65R-15 Goodyear Eagle GT tires and seven-by-fifteen-inch alloy wheels-nothing less than stellar to begin with-have been upgraded to broad-shouldered P245-50VR-16 Eagle VR50 tires on eight-by-sixteen wheels.  These tires have the same unidirectional "gatorback" tread pattern as those pioneered on the Corvette, and they are nearly as wide.


You'll also notice that the IROC-Z squats more than a half-inch lower than a standard Z28.  And the new front wheels position the front tires another quarter inch outward for better steering geometry.  The IROC-Z rear wheels, on the other hand, pull the fat tires in by about an eighth of an inch to clear the bodywork.   (The front and rear wheels are no
longer interchangable.)


A number of other important revisions are part of the deal, too.   The front structure is reinforced with a new crossmember, that the engineers call the "wonderbar"; bolted in place just below the front anti-sway bar, it stiffens the car's front structure during high-g cornering.  The suspension's caster angle is up from three degrees to four for better straight ahead highway stability with the wider rubber.  About twenty percent more steering effort has been dialed in.  The 1984 Z28's spring rates were deemed optimum, so they remain unchanged, but Bilstein gas-pressure shocks are now in place at the rear to improve ride quality and control over chatter bumps.  Front shock-absorber valving has been revised as well.


The IROC-Z also looks a little bit different-and even handsomer, we think-than Camaros of yore.  All 1985 Z28s will recieve a new, more rounded nosepiece, a deeper front air dam, and lower rocker-panel skirts.  (The new contouring does not improve the Z28's 0.34 drag coeffient however.)  IROC-Z s are distinguished by a pair of nostril-mounted driving lights and by a one-color paint treatment; standard Z28s will have a lower band of contrasting color, as before.


Once you've opted for the primo chassis pieces by ordering the IROC-Z package, you've still got to choose a power team.  Chevrolet allows you to fill an IROC-Z's engine bay with any of three five-liter V-8's.  You'll want to pass on the 165-bhp LG4 base engine, of course.  Once you do, your decision becomes easier.  If you want a five-speed manual gearbox, it comes bolted only to the carbureted 190-hp L69 V-8, which is carried over from last year.  If you'd rather be shiftless, you get a four speed autmatic and Chevy's newest motor, the LB9, with electronic port fuel injection.


This is an engine worth saying something about.  Originally planned for the Corvette, it became a Camaro/Firebird exclusive when Chevrolet decided their sports car needed a full 5.7 liters of displacement.  (The 1985 Vette V-8, however, shares the same intake plenum, long tuned intake runners, mass airflow sensor, and other hardware.)  In IROC-Z tune, the LB9 is a sweetheart, thumping out 215hp at 4400rpm.  The only problem with all this power, according to well-placed sources, is that it exceeds the torque capacity of the Borg-Warner T5 five-speed manual gearbox used elsewhere in the line.  That's the reason no manual transmission is ordered is offered with the fuelie engine and probably won't be until 1986.


Once the drivetrain decisions are sorted out, you can option the IROC-Z just like any other Z28.  In terms of interior appointments, little is changed from last year.  Our pair of factory pre-production prototypes were fitted with a full load of extras, including Lear Siegler's latest attempt at a multiadjustable driver's bucket.


What rolls off the assembly line when you've checked all the right boxes should be a very happy GT car.  Gone are all traces of crudeness.  The IROC-Z's way with the road is now admirably supple and smooth.  It keeps all four paws firmly planted, even over bombed-out pavement-and it does so with impressive ease.   The steering is delightfully accurate, and the fat tires seem to stick as if they has been dipped in glue.  No doubt about it, you can make graceful moves in this car now; no matter how hard you push, it doesn't get ruffled.  Even the Lear driver's seat finally feels right.


And this car ever go.  The L69-and-five-speed combination blasts to 60 mph in 7.5 seconds and doesn't quit until it's hit 138 mph.  We likes this powertrain the best because it gives you a slick manual gearbox to play with.


Those of you who opt for the automatic and the fuel-injected engine won't exactly be deprived, however.  The new motor, quite simply, is a gem.   When you snap your throttle foot down, the exhaust barks and you get shoved in the back as if you were in a barroom brawl.  Sixty miles per hour rushes at you in seven seconds flat, there's smooth power everywhere in the rev range, and an honest 140 mph would show on the single-pointer speedo if the numbers didn't meekly come to a halt at 85.


Unfortunately, the automatic gets all confused around town, trying to serve your needs while providing the best fuel economy.  Its constant cycling is nothing short of annoying.  What's more, the shift linkage thwarts any attenpt to override the gearbox manually.  The automatic's subpar performance and the standard-for-Z28 brake pedal mushiness are only over-the-road problems left to be rectified.


Clearly, we're talking well-rounded performance here.   Chevrolet has also been working on the squeaks, rattles, and other mechanical maladies that made such a disaster of our 1982 long-term test car, so there's hope on the reliability front as well.


While it's too early for proclamations, we have to admit that hyperbole is reverberating around the edges of our collective editorial mind.   Without a doubt, the IROC-Z is the best all-around Camaro ever.  It will probably turn out to be one of the season's juiciest high-performance values, able to hold its head high among some of the world's best GT machines.  All of which leaves the IROC-Z in a unique position in the automotive cosmos.  Not only does it commemorate; it's worthy of commemoration.

Acceleration

Manual

Automatic

30 mph

2.3

2.4

40 mph

3.8

3.8

50 mph

5.3

5.2

60 mph

7.5

7.0

70 mph

9.8

9.4

80 mph

12.4

12.2

90 mph

15.4

15.0

100 mph

20.5

19.8

110 mph

28.8

26.1

120 mph

41.7

35.5

130 mph

 

51.4


 

Standing quarter-mile

Automatic: 15.2 sec @ 91 mph

Manual: 15.4 sec @ 90 mph

 

Top speed

Automatic: 140 mph @ 4550 rpm

Manual: 138 mph @ 4400 rpm



 
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