IROC and I Roll Over 5.0 Mustangs
Steve Magnante – Photography by the Author
Does anyone remember the ’80s? This writer sure does. It was a time of awakening. A time of rebirth. The dreaded “Smog ’70s” were a thing of the past. Chevrolet launched two blinding stars into the automotive firmament: the C4 Corvette in 1984 and the Third-Generation Camaro in 1982.
Chevrolet didn’t scream and shout when it gave an IROC-Z the heart of a Corvette. The Tuned Port Injection LB9 305 and B2L 350 were extra cost on the IROC-Z and shared the same stickers below the rocker panel emblems except B2L cars gained the discreet 5.7 prefix. Street rats knew the score.
Though the brutal big-blocks of the Supercar ’60s never returned, a new emphasis on braking and handling crutched the fact that horsepower levels above the 200 mark were an extreme rarity.
Virtually identical in appearance to the TPI 305, the 350’s 4.00-inch bore is 0.26-inch larger. Both share the same 3.48-inch stroke. Camaro-bound 5.7s lacked the Corvette-spec L98 5.7’s aluminum cylinder heads and exhaled through iron log-style manifolds versus Corvette’s stainless headers. This accounted for the Corvette’s superior 240 hp and 345 lb-ft.
As good as the ’82 Camaro was (and is), the real fun began in 1987 with the availability of the then-massive Corvette L98 350 as an alternative to the 305. Sold as RPO B2L, for an extra $1,045 top-tier IROC-Z buyers had 225 hp and a yummy 330 lb-ft of torque under foot.
Often overlooked, this slender cowl-to-strut tower brace is only seen on IROC-Z and Z28 applications. The C60 air conditioning system was an extra $745 and was installed on 104,642 of the 110,739 Camaros built in 1989. IROC-Zs ordered with the G92 performance axle package (1,426 built) but no air conditioning became eligible for the 1LE Special Performance Components Package, which included an oil cooler, upsized four-wheel disc brakes, 145-mph speedometers, aluminum driveshaft, fuel tank baffles, and other goodies. Just 111 1LEs were built in 1989.
Life was good except for the fact this 5.7L torque-maker wasn’t offered aboard lesser (non-IROC) Z28 Camaros, where the 190hp LB9 Tuned Port 305, with 285 lb-ft, was king for an extra $745. The sleepy 165hp LG4 throttle body 5.0 V-8 was the base Z28 engine.
In 1989, IROC-Zs were available in bright blue, bright red, dark red, black, and white. Though available on other Camaros, light blue and medium gray were not offered on the IROC-Z in 1989. Street rats knew to look for deleted halogen foglamps astride the front license plate pad, a sign of 1LE hero status.
This month let’s pay our respects to an ’89 IROC-Z with the subtle-yet-earth-shaking “5.7L” prefix displayed ahead of the Tuned Port Injection stickers on the rocker panel extensions and rear bumper.
Contrary to myth, IROC-Zs and Z28s shared the same trunk spoiler and rear bumper cap. The stick-on plastic engine emblem on the driver side reads Tuned Port Injection on LB9 305 cars and 5.7 Tuned Port Injection on this B2L 350 car. Aside from the “5.7” logo (which is molded as one with the rest of the emblem) the emblems share the same font and colors. Very subtle stuff.
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Like the ’74-81 Pontiac Trans Am’s “faker shaker” hood, the ’85-90 Z28 and IROC-Z louvered hood was strictly for show. Shaped like a NACA duct, the only functional units appeared in 1982 and 1983 on LU5 Cross Fire Injection 305s, which utilized solenoid-activated rectangular flapper doors to admit cool air into the sealed air cleaner lid. Often forgotten is that ’82-83 Z28 hoods were fiberglass.
Love ’em or don’t, CC1 T-tops were popular among IROC-Z buyers. Priced at $866, they make sunny days more fun but are shunned by road racers for their negative impact on body (and thus chassis) stiffness.
The IROC-Z was the first Camaro with 16-inch rolling stock. The factory issued 245/50-VR16 Goodyear Eagle GT tires were unidirectional and could deliver 0.92 g’s on the skidpad. The 16×8 rims and tires were standard on IROC-Z until 1988 when they became option N96 for $468, as seen here.
Unfortunately, the L98 350 was only offered with an automatic. GM knew the Monza-based 7.62-inch ring gear wasn’t up to its 330 lb-ft behind a stick. While V-6 and throttle body 305s got 115-mph speedometers, IROC-Zs with either TPI engine got the 145-mph speedometer seen here. Before 1988, speedometers used the absurd split-screen 85-mph English/140-kph Metric unit first seen in 1982.
Continuing the Corvette tradition of the ’60s, where the optional engines got higher tachometer redlines, 350 tachometers go red at 5,400 rpm, 400 rpm higher than all 305 units. The aftermarket Grant padded steering wheel is a typical period accessory.
Crusted in typical New England rust, the unique torque-arm rear suspension was first seen under the ’75 and ’76 Cosworth Vega and ’75-up Chevy Monza. The amazing thing is how Chevrolet stuck with its minuscule 7.5- and 7.62-inch ring gear all the way through 2004 beneath the mighty LS1-powered fourth-generation Camaro. GM engineers relied on tire spin to save the small differential from harm.
Oddly, sibling division Pontiac recognized the Camaro axle’s inherent weakness and put Australian sourced BorgWarner axles under top-tier Firebird performers like this ’89 Formula 350 (which uses the same TPI 350 as the IROC-Z). Chevrolet did offer a Dana 45 “crate axle” for F-bodies in the mid ’80s but it was strictly an over-the-counter item. Factory installation would have added greatly to the 350 IROC-Z legacy.