The '57 fuelie: great car, but not a benchmark.

       Muscle Car era "Big-Blocks". Their engines were obscenely powerful, but a three-link rear suspension and their weight left them lacking in handling. No world standard there, either.

       Chevrolet told us the 1984 Corvette benchmarked world-class sports cars. Admittedly, it was a huge improvement over the previous platform, in production since 1963, but with only 205hp; Chevy's claim rang a bit hollow.

The Stuff of Benchmarks
 

       Executives at Ferrari, Lamborghini, Porsche, Jaguar and other manufacturers of high-performance automobiles awoke to find hell had frozen. At Geneva, Switzerland's International Automobile Show that morning, upon their first look at an almost painfully bright, Competition Yellow ZR-1; people were aghast. Exclamations in a score of foreign tongues asked, "The Americans...they have done this?!"

       Their amazement was well-taken.

       Here was a production car with a top speed of 180 mph, a standard few automobiles can meet, today, much less in 1989. The ZR-1 did the quarter in the low 13s or, under ideal conditions, even high-12s, another performance tough for any production car of that period to equal. It was a car with outstanding handling and braking. It was a car with a 375 horsepower engine having a 7000 rpm rev limit and a specific output of 1.07. This engine got outstanding fuel economy, idled smoothly as those in the finest luxury sedans and met U.S. exhaust emissions standards for not only 1990, but 1991 and 1992, as well. Say, "Benchmark." in five languages and you've got the ambiance.

       Geneva showgoers learned that technology abounded in the ZR-1. Not only was its engine an all-aluminum, dual-overhead-camshaft, 32-valve, electronically fuel-injected V8, but the car had an electronic ride control system, a six-speed transmission and huge 315/35ZR17 Goodyears at the rear.

       All this from Chevrolet, a company Europeans vaguely understood to make hulking pickup trucks driven by cowboys and gas-guzzling Caprices driven by cops on American TV. Indeed, you needed snow shoes in hell that day.

       When the car went on-sale in the fall of 1989, its cost took-off like a Patriot missile. In spite of prices as high as $120,000 that fall and winter, 3049 ZR-1's were sold in model year 1990. The ZR-1 was in production for six years with 2044 '91s, 502 '92s and 448 each for '93, '94 and '95 being built. All ZR-1's have unique vehicle ID numbers. By the end, in May of 1995, the base Corvette price had gone up $4806 and the ZR-1 option had gone up $4242. The 448 Corvetters lucky enough to buy a '95 ZR-1 paid $68,643.00 for the privilege.
 

Power Makes Royalty
       ZR-1 began with an engine. Corvettes have always been about what's under the hood and this case was no different.

       The Wayback Machine, again. Set it for winter '83/'84.

       At Chevrolet, life was good. It made history the previous spring with the all-new, '84 Corvette. Twelve months later, GM's Bowling Green Assembly Plant was still running wide-open to meet demand.

       Back in Warren, Michigan, Corvette Engineering Director, David R. McLellan, and other GM executives were anxious about the future. The idea of other cars booting Corvette, ass-over-teakettle, off the top of the "hill" in the late-'80s was alarming.

       They knew a good defense would be a strong offense, so Corvette needed more power-lots more. To get benchmark performance, McLellan needed about double what the Vette had at the time. Such an engine, also, must have outstanding drivability, good fuel economy, meet quality/reliability/durability (QRD) targets and satisfy Federal emissions standards. All this was science fiction in the winter of '83/'84.

       Early concepts were turbocharged V6s and V8s. The V6 turbos had undesirable noise and vibration characteristics. The turbo V8s, were perceived as "low-tech". Next, GM looked at dual-overhead-camshaft (DOHC) heads for the existing, Small-Block V8. At the time, engineering resources for a low-volume, DOHC Corvette head were unavailable inside GM. Outside help came in the form of England's Lotus Engineering. Lotus decided there was no way a DOHC Small-Block could fit through the Corvette's frame, a requirement of the car's "bottom-loaded" assembly process. In a meeting at Detroit on April 3, 1985, Lotus told GM if it wanted 400 horses, a new engine was required. Six weeks later, GM approved the "LT5", its first new V8 in over 20 years.

       The rest of the four-year development by Lotus and GM should be a separate, future article here on the ZR-1 Net web site. In short: the two companies broke new ground in production high-performance engine design, performance and QRD.

 The result was a magnificent powerplant.

       In a press conference on the afternoon of the car's introduction at Geneva, McLellan said the goals of the LT5 development were to "....1) create a car that is second to none in acceleration-nothing less than the fastest production car in the world, 2) Achieve that kind of performance without sacrificing drivability-not only at the high end where you expect fast cars to drive well, but at the low end, too, 3) Package all this leading-edge performance and drivability into an engine that could still deliver good fuel economy, and 4) design this engine to fit between the rails of the existing Corvette's engine compartment-a brand-new engine, but not one that would require a totally new car."

Inside LT5
 

       The cylinder heads are cast aluminum. Each has 16 intake ports, four-valves per cylinder, cloverleaf combustion chambers, centrally-located spark plugs and 16 exhaust ports, siamesed at the port exits. The valves are flash-chromed steel and the exhausts have stellite faces. All are fitted with dual valve springs.

       Each head has two chilled, cast iron camshafts. The intake cams have two profiles, the secondary profiles being more aggressive than the primaries making for good drivability in light load operation but plenty of air flow at wide-open-throttle (WOT). The cams work bucket-type, hydraulic lifters. A "half-speed-idler" gear, located where a camshaft sprocket would be on a pushrod engine, is chain-driven off the crankshaft. Duplex, roller cam chains drive each pair of cams from the half-speed-idler. Hydraulic cam chain tensioners eliminate chain slack.

       Each head is fitted with a die-cast "injector housing" which holds eight primary and eight secondary fuel injectors and has throttle plates in the secondary intake ports. Under light load, the "Secondary Port Throttles" are closed to raise air velocity in the primaries which enhances drivability, torque output and fuel economy. Under heavy load, the port throttles open, making all 16 intake ports available for air flow. The port throttles and secondary injectors are computer-controlled and work together. On the exhaust side, the heads are fitted with fabricated stainless steel exhaust manifolds with integral, close-coupled, catalytic converters.

       LT5 was the first application of sequential electronic fuel injection (SEFI) to a GM V8 engine. SEFI pulses injectors according to the engine firing order offering better drivability, fuel economy and exhaust emissions compared to previous, "batch-fire" systems. Typical of modern cars, LT5's fuel, ignition and emissions systems were operated the engine computer or "electronic control module" (ECM) located, under the hood, at the base of the driver-side A-pillar.
 

       If ZR-1 was simply a '90 Vette with a high-tech, 375hp engine, the car would have been a King. Heck, it wouldn't even have been a princess. Other features contributed to its benchmark status.

Selective Ride

       Next to the LT5, this The King of the Hill Corvette's most intriguing feature is "Selective Ride Control" (SRC). Developed and manufactured by Bilstein, the German maker of ride control products, "FX3", as some call it because of its RPO code, was a technical milestone for a high-volume car in the early-'90s.

       Bilstein's original SRC work was done for the $230,000, limited-production 1987 Porsche 959. Chevrolet and Bilstein repackaged the hardware, recalibrated the controller software, then introduced it as an option on 1989 Corvettes. A year later, ZR-1 got it as standard equipment.
 

       Selective Ride was not just marketing-driven gadgetry. It has a wide bandwidth of damping making a ZR-1 ride nicer in normal driving situations but handle better when driven hard. While SRC was replaced in 1996 with a more marketing-driven ride control system called "Real-Time Damping", it wasn't until the late C5 era and "Magnetic Selective Ride Control" introduced for 2003, did any Corvette have a ride control system that contributed as much to both at-limit handling and ride as did SRC.

Six-Speed Stick
       The only ZR-1 transmission is the ZF, S6-40, six-speed manual. Imagine it as a wide-ratio, four-speed with two overdrives. Its low first gear, combined with a 3.45 axle ratio, makes a first gear drive line ratio of 9.27:1. That's ideal for the ZR-1's traction and power-to-weight ratio and insures great performance and drivability at launch. Intermediate ratios were chosen to use the LT5's torque curve for maximum acceleration. Fifth is your go-fast gear in which the car reaches its 180-mph, top speed a little after the LT5 hits peak power.

       Sixth is a gas mileage gear. In sixth, at freeway speeds, the engine runs about 1300 rpm. Even at that, the LT5 generates more than enough torque to drive the car. ZR-1's get great fuel economy, in-part due to the tall sixth gear but, also, because of some electronic magic, computer-aided gear selection (CAGS). During certain low-speed, light throttle operation, when the driver shifts out of first, a solenoid on the side of the S6-40 forces a shift to fourth. This does not "lug" the engine and contributes to fuel economy such that a ZR-1 was EPA-rated at 25 mpg/highway and owners paid no "Gas Guzzler" tax. Few ZR-1 competitors were capable of that benchmark efficiency.

       Everything about a ZF is big. Its case is massive. The main- and countershafts look like they belong in a truck transmission and the gears, machined out of high-quality steel forgings, are beefy.

       For all its size, you'd think the S6-40 shifts like a truck transmission, but it doesn't. A precision, internal rail-shift mechanism eliminated adjustments, decreased shift effort and refined shift feel. Composite (sintered-bronze/stainless-steel/steel) synchronizer rings reduce shift effort and improve durability. Dual-cone synchros were used in first and second for additional improvement in shift quality. All gears ride on needle bearings and shafts are on roller bearings. The oil in a ZF six-speed is a low-viscosity, multi-weight, gear lubricant formulated for optimum lubrication, synchronizer action and shift feel.
 

Wide-Body, Fat Tires
 

       Goodyear had been OE on Corvettes since 1978 (it still is, today) and was the obvious choice when GM needed special ZR-1 rear tires to supply extra traction to get the LT5's torque down during hard cornering and acceleration.

       To cover these big Goodyears, initially GM considered fender flares but the result was unattractive. GM Design Staff then came-up with better-looking, wider, rear bodywork. The new doors, rear fenders and rear fascia were responsible for nearly a quarter of the tooling cost of the entire program but gave the ZR-1 its unique appearance.

       There were other features, the design and engineering of which were driven by the King-of-the Hill project, but were introduced in earlier years. Examples are: larger front brakes and revised suspension geometry in 1988 and a innovative, low tire pressure warning system in 1989.
 

Our Quest for an Original ZR-1

       To better understand, we went looking for the King of the Hill. Our quest led 55 miles west of Los Angeles to Camarillo, California and Doug Minnis, owner of the Dark Red Metallic, 1990 ZR-1 you see in these images.

       Minnis' car was built in the final 2/3rds of model year 1990 production on April 20, 1990. It has weathered the past 14 years in excellent shape. Its only upgrade has been a set Goodyear Eagle GS-C tires, supplied by Goodyear prior our testing for this article to replace the car's original but worn-out, Eagle ZR50s. Otherwise, Minnis' car is original, right down to its special, LT5 spark plug wires.

       "Major component replacements? None really." Doug told us. "Only routine maintenance items...brakes, coolant flush, fluid changes, and that sort of thing have been done. Paint is original. While this car has relatively high mileage (51,502) for a ZR 1, it has never given me an ounce of trouble. I just plain drive it!"

       Start an LT5 and right away you note the engine's refinement. I've driven many ZR-1s, but its smooth idle always pleases me. Back when the car was introduced, a stunt performed by GM folks to illustrate the engine's smoothness was to stand several nickels on edge, atop an idling LT5's intake plenum.
 

What's it Like Out There?
       It was time to understood one reason why hell froze in the automotive world back in 1990. The only restrictions Doug put upon us for this driving impression were: no drag strip launches and no powershifting.

       I got the car rolling about five mph., then floored it. Doug's ZR-1 took off like a rocketship. As the engine neared peak torque, the rear tires broke loose a little. Amazing! Tires 11-inches wide and the car was spinning them. Ok-we lacked drag strip traction and, on a cold day, the engine was making a ton of power, so maybe those Goodyears broke loose a little easier.

       I pedaled it. After the tires hooked, I buried the gas, again. LT5s, peak around 6000 rpm., so for best acceleration, shift about 6500. Lift-clutch-shift and we're in second, pulling hard. Things happen slower in second so it may be the first time ZR-1 "newbes" notice the characteristic "howl" a 32-valve V8 makes above 4500 rpm. It's music to our ears.

       Grab third and we're really hauling. As the motor goes by five-grand, again, the LT5 sings some more. We're nearing 100 mph so wind and tire noise to add to the intensity of the moment.

       About 115, I tag the rev limiter, then lift. The way a ZR-1 is geared, you go though drag strip traps at the top of third so, what we've just done is a quarter-mile pass, less a hard launch and powershifts.
 

       "That's the first time I've ridden over here in a ZR-1 running that hard." Doug commented. "It's not quite as fun as driving, but still, these are pretty amazing cars, aren't they?"

       "'Benchmark', indeed," I quipped, "especially when you consider this car was built 15 years ago and conceived 20 years ago. What do you say we hop on the freeway and see how nice your car cruises, then maybe catch a late lunch?"

       U.S. 101 is the major highway through the area and, like some California freeways, in places it suffers the dreaded, "tilt slab" condition. Over time, individual concrete slabs tilt, developing a 1/8-in. or so drop-off. At certain speeds, this gets some cars into a pitch oscillation. GM engineers have a name for this ride motion: "L.A. Freeway Hop." Compared to Corvettes without it, Selective Ride Control, in the "Tour" mode, makes an improvement in ride quality. Freeway Hop is great for feeling SRC's other modes work, too. Go to "Sport", harshness increases. Go to "Perf", the ride really stiffens-up.

       Any car this old will have low-level squeaks and rattles and Doug's is no different. Otherwise, interior noise level is acceptable. The engine, loafing at 1600 rpm, is smooth and virtually silent. The one ZR-1 creature comfort not to my liking is the "Delco-Bose" sound system. I've never been a fan of its lack of a balance control. Bottom line: highway cruising in a ZR-1 is quite pleasant. This refinement is another reason why ZR-1 benchmarked sports cars of the early-'90s.

       I end my first day with a '90 ZR-1 doing lunch with Doug at one of nearby Oxnard's culinary treasures: "Killer Burger". Want a tasty hamburger on a home-baked bun and some lip-smackin' good fries? You'll find them there.

Ride and Handling
       Three weeks later, I meet Doug Minnis a second time for a handling "test". We picked a route north out of Camarillo, towards the mountain resort of Ojai, then west towards the coastal town of Carpinteria. We stopped at a 76 station for some 91-oct. unleaded, set the ZR-1's Goodyear GS-Cs at 35 psi. then headed for the hills.

       North on State Route 33, we have the windows up, the automatic air set for 70 and the stereo on. I'm having fun: up-and-down the ZF's lower gears, feeling the rack-and-pinion steering's crisp response and noting the car's powerful brakes. SRC is in "Sport", damping just right for how we're driving. We're cornering fast but not hard enough to tax the car's handling. The big Goodyears don't even squeal-at least, not yet.

       Cruising along in third, to gauge the LT5's flexibility, rather than shifting, I simply floored-it. Ah, yes...nothing like American V8 torque. At wide-open-throttle and 1500 rpm there's no stumble, no misfire; the engine just begins to pull. 3000 rpm and it's pulling harder. By 4500, the LT5's howling once more. The digital speedometer counts triple digits.

       About 6700, I shift to fourth. With half-a-mile or so of good road ahead, I'm still hard on it. At 135, the ZR-1 is rock solid on the road and...still accelerating. At 6500, I shift to fifth. Adrenaline is pumping. A moderate left-hander is coming up quick. I glance down at the IP: 153 mph. Ok. That's enough on a two-lane public highway.

       I lift, downshift, smoothly apply the brakes and watch the IP display slide backwards...140...125. I heel-and-toe another downshift...105...maybe a little brake fade due to stock pads are a bit old...95, then 80. I ease-off the brakes a bit, steer into the turn, then release the brakes and hold my speed.

       Exiting the turn I roll-on the power. I'm WOT for a short time. I brake for another turn. It's like this for several miles. Handling is very good-a trace of understeer right at the limit, but the Goodyears are predictable and let you know where the limit is. If you don't overdrive the car, the understeer is minor. Selective Ride Control provides good control of the low-frequency body motion and high-frequency wheel movement one gets on roads like this.

 
       Near the end of our thrill-ride over SR150 towards the coast, there's some tight turns. You're in third gear and sometimes second. Here is where unskilled drivers may find one of the ZR-1's handling quirks. Due to marginal, low-velocity, rebound shock valving at the rear, if you enter a turn, lift quick then brake hard, the car gets loose and can even come around on you. Avoid this by not going into a turn too hot and avoiding abrupt transitions between throttle and brake. Other than this, ZR-1s are pretty forgiving cars.

Benchmark...Indeed
       Just outside Carpinteria, I zap across a bridge, nail the brakes, downshift to first and make a tight, left turn onto U.S. 101. I accelerate hard though second then granny shift to sixth. I set the cruise control at 65 as I merged into eastbound lanes, headed back to Camarillo then put the windows up, the air back on and turn on the radio.

       Now you know why the ZR-1 was a world benchmark for sports cars of the early-'90s. It's a car that you could drive hard for sustained periods or blissfully cruise the highway with the air and stereo blasting. In either case, the powertrain and chassis deliver performance and refinement that was virtually unparalleled in sports cars of the period and is still considered quite good, today.

       Addressing media on the crisp day back in March of 1989, Dave McLellan, apparently a master of understatement, summarized the car in a widely-quoted sound byte, "The ZR-1 is Corvette...only more so."

       We agree.

Owner's View
       I have been a Corvette fanatic for as long as I can remember. As a twelve-year-old, I spent countless hours in my neighbor's garage sitting in his new maroon-on-black, '62, two-top car, shifting gears and dreaming of the day I could drive. I have owned Corvettes all of my life and, up until the ZR 1, thought the only Corvettes worth having were old ones, that is, pre-1972.
 

       The car is a marvel of engineering. The team work that developed, designed, and built the car is a fabulous story. The ZR-1 was ahead of its time was an amazing feat given the culture of a company like General Motors which is not typically given to projects of this nature.

       But nothing can prepare a person for what it is like to drive this kind of car. It is nothing short of awesome. I get excited every time I drive it. The power is incredible. The handling is fantastic. With the adjustable ride it behaves like a "normal" car when needed. It has it all: raw power, awesome engine sound, great cornering, climate control, cruise, Bose sound system and it looks great too, especially from the back with the wide 315's.

       I also own a (1996) Grand Sport which I purchased after the ZR-1. I was so impressed with that car, too. I absolutely love them both. While I'm sure there are lots of "Super Cars" built since these, for the money, all things considered; this car was and is a great value. I purposely bought a car with enough miles on it so putting additional miles on it would not be an issue, and I'm glad I did, I drive it all the time. After all, it's never too late to have a happy childhood.
--by Doug Minis
 

Specifications (as tested)

Original price: $31979.00, base Corvette coupe

Standard equipment: 245hp V8 with 4-speed automatic, four-wheel power-assisted disc brakes w. ABS, aluminum wheels, lift-off roof, air conditioning, remote heated mirrors, power windows, power locks, tilt steering column, cruise control, rear window defogger and fog lights.
Optional Equipment: $27.016.00, (ZR-1) Special Performance Package. Incl. 6-way power driver (AC1) and passenger seats (AC3), leather sport seats (AQ9), Electronic Air Conditioning (C68) Selective Ride Control (FX3), 375hp 5.7L SEFI DOHC V8 (LT5), six-speed manual transmission (MN6), Delco-Bose stereo w. CD and cassette (U1F) and low tire pressure warning system (UJ6). Also incl. "Solar Ray" windshield, special bodywork and 315/35ZR17 tires.

Engine
Type: 90° all-aluminum V8
Bore x stroke: 99x93mm (3.90x3.66 in)
Displacement: 5727cc (349.77 cubic inches)
Compression ratio: 11.0:1
Horsepower: 375hp@5800rpm
Torque: 370 lbs/ft@4800rpm

Valve gear: chain-driven, dual overhead camshafts, direct-acting hydraulic lifters, dual valve springs, four valves per cylinder.
Induction system: Computer-controlled, sequential electronic port fuel injection w. 16 injectors.
Lubrication system: full pressure with crankshaft-driven gerotor oil pump, full-flow oil filter and thermostatically-controlled engine oil cooler.
Exhaust system: stainless steel manifolds, dual 3-way catalytic converters, dual exhaust and dual mufflers.
Electrical system: 12-volt w 120-amp alternator and 690 CCA battery

Transmission
Type: ZF S6-40 six-speed manual.

Rear axle
Type: Hypoid gear-set in chassis-mounted aluminum housing
Ratio: 3.45:1
Differential type: clutch-type, limited slip
 

Steering
Type: Power-assisted rack-and-pinion
Ratio: 15.6:1
Turns, lock/lock: 2.25
Turning circle: 40 ft.
 

Brakes
Type: four-wheel, hydraulic disc brakes with power-assist and antilock braking system Disc diameter: front 12.8-in., rear: 11.9-in
Swept area: 111.91 sqin., front'; 91.295 sqin., rear

Chassis and body
Chassis type: Welded steel uniframe
Body material: Glass reinforced plastic or sheet molded compound
Body type: 2-door, 2-seat coupe
Layout: Front-engine, rear-drive
 

Suspension
Front: Independent short arm/long arm (SLA) with aluminum control arms; aluminum steering knuckle; transverse, glass-epoxy composite, mono-leaf spring, 30mm stabilizer bar and computer-controlled, adjustable, mono-tube dampers
Rear: Independent five-link with 2 aluminum trailing arms; 1 alum. lower control arm; 1 alum. axle shaft; 1 steel camber control rod; aluminum knuckle; glass-epoxy composite, mono-leaf spring; 24mm stabilizer bar and computer-controlled, adjustable, mono-tube dampers. Wheels: front: 9.5x17-in aluminum, rear: 11x17-in.
Tires: Goodyear Eagle ZR50, front: 275/40ZR17, rear: 315/35ZR17

Weights/Measures
Wheelbase: 96.2-in.
Length: 177.4-in.
Width: 74.0-in.
Height:: 46.7-in.
Front track: 59.6-in.
Rear track: 61.9-in.
Curb weight: 3479 lbs.

Capacities
Crankcase: 7.6-qt.
Cooling system: 16.7-qt.
Fuel tank: 20-gal

Performance (typical)
0-60: 4.3-4.6 sec.
1/4-mile: 12.8-13.1 sec. at 109-112 mph
Top speed: 180 mph
Braking 60-0: 125-135 ft
EPA fuel mileage: 16 mpg city/25 highway

Production
3049 for 13% of total 1990 Corvette production

About the Author:
While some credit the June 1987 Car and Driver for the first publication of details of the ZR-1, it actually was Hib Halverson who broke the ZR-1 story several months before. Working for a long-defunct and largely forgotten magazine, Corvette Illustrated, Halverson was the first to publish accurate details of the ZR-1 and the LT5 engine in the April 1987 issue of that magazine.