So what was the C4 ZR-1 all About ?

[teamzr1]

In 1987, rumors of an all-new, high performance Corvette built upon the fourth generation platform began circulating among the automotive press.
Dubbed the “King of the Hill,” the secretive supercar was said to be a world-beater, and in March of 1989, GM debuted its impressive Corvette ZR-1 at the Geneva Motor Show.
This year marks the 25th anniversary of the ZR-1’s market debut, and while a mere 6,939 were ever built, the car remains a memorable piece of Corvette history, as well as a bridge from performance Corvettes past to the present.
The 1990 car didn’t originate the ZR1 moniker (though it did originate the hyphenated ZR-1 name). From 1970 to 1972, Chevrolet offered an RPO ZR1 option for the Corvette that included a 350-cu.in., 370-horsepower V-8 mated to a close-ration four-speed transmission; heavy-duty brakes; a transistorized ignition; an aluminum radiator; and a heavy-duty suspension.

Wisely, the configuration was not recommended for street driving, but those opting to exercise their Stingrays in a closed-course environment surely saw the benefits of this package.
When the fourth-generation Corvette made its appearance for the 1984 model year, the car’s handling won near-universal praise.

Its 205-horsepower 350-cu.in. V-8, however, did not, and within a few years of launch the car’s underwhelming performance began to have an impact on sales. GM had been working on an in-house performance engine option of its own, but building one that maintained the civility needed for everyday driving proved challenging.

Enter partner Lotus Group, which GM had acquired in a 1985 deal. Working in conjunction with the Chevrolet, Pontiac, GM Canada (CPC) Division, Lotus developed an aluminum-block 350 V-8 that utilized double overhead camshafts and four valves per cylinder and proved capable of producing 375 horsepower and 370 pound-feet of torque.

It was the testing of this engine (a variant of which would appear in the 1986 Corvette Indy concept) that led to the rumors of a “King of the Hill” Corvette, and in March of 1989, GM was ready to show its hand.
The Geneva debut was hardly accidental, and GM made sure to invite press from around the globe for the car’s European test drive.

Most media outlets wasted no time heaping praise on the car, which proved capable of running from 0-60 MPH in a little over four seconds, on its way to a top speed of 175 MPH. Car and Driver even called it “The Corvette from Hell” for its performance potential, and as if to illustrate that the ZR-1 would not suffer fools behind the wheel, a horsepower-limiting valet lockout was standard equipment.

In addition to the Lotus-designed V-8 beneath the hood, the ZR-1 featured a three-inch wider rear track, necessitated by its oversize 315/35-17 rear tires (which humbled the base Corvette’s 275/40-17 rear skins).

The change required new doors, as well as a new rear fascia that took a convex shape to distinguish it from lesser Corvettes (for the 1990 model year, anyway). Taillamps on ZR-1 models were rectangular in shape, but in profile, the ZR-1 looked very much like a base model Corvette, albeit one with different wheels.

Neither GM nor Lotus had the ability to construct the ZR-1’s LT5 V-8 in sufficient quantities, so production of the hand-built engine was awarded to Mercury Marine in Stillwater, Oklahoma.
Assembly proved costly, as did the significant changes to the Corvette’s body to accommodate the ZR-1 changes, and the car was priced accordingly.
In 1990, a base model Corvette could be purchased for $31,979, yet the cost of the ZR-1 package alone added another $27,015 (or nearly 84.5-percent of sticker price) to the car’s label.
Despite this, and despite dealer markups that reportedly doubled the price, initial demand was respectable

To allay fears that the ZR-1’s aluminum engine lacked durability, a production model was pulled from the assembly line in the spring of 1990 and sent to a proving ground in Fort Stockton, Texas.
There, the Corvette proceeded to set a series of speed and endurance records, covering 5,000 kilometers at an average speed of 175.71 MPH; 5,000 miles at an average speed of 173.29 MPH; and running for 24 hours at an average speed of 175.88 MPH, covering over 4,200 miles in the process.

For the 1990 model year, GM built 3,049 examples, followed by 2,044 in 1991; 502 in 1992; and 448 each year from 1993 to 1995, when ZR-1 production ended.
Even a bump in output to 405-horsepower for the 1993 model year failed to reverse falling sales, but increasing horsepower in other Corvette models was also to blame.

A new LT-1 V-8, introduced for the 1992 model year, made 300 horsepower and 330 pound-feet of torque, making the argument for spending an addition $31,683 (the ZR-1’s package price in 1992) that much harder to justify.

 

[teamzr1]

When Chevy looked to take its fourth-generation Corvette to the next level of performance, it reached out to Lotus, which was at the time under the GM umbrella.
Chevrolet wanted to build a high-powered Corvette with an exotic, world-beating engine, so Lotus took the lead in developing a V-8 unlike any small-block that Chevrolet had ever built.

Around 25 development mules were deployed by Lotus to test this new, "King of the Hill" Corvette and its engine, and only two of them survived in running and driving condition.

One is currently up for auction on Cars & Bids.
It’s part of the Lingenfelter collection and has all the hallmarks of a development prototype.
For example, while it’s equipped with a ZF six-speed manual, it bears the center console of the C4’s Doug Nash 4+3 overdrive transmission and the 315mm-wide rear Goodyear tires have "Not For Sale" molded into the sidewall.

According to the listing, this car was saved from a British scrap heap by a Lotus employee that restored the car to its present condition. Its blue exterior and blue interior are pure late-’80s perfection.

Of course, the crown jewel of this King of the Hill is its DOHC LT5 V-8, found only in the C4 Corvette ZR-1. While it uses the same bore spacing as all Chevy small-blocks before it-and since-at 4.4 inches, that’s where the similarities end. The LT5 has four-valve heads each topped with a pair of camshafts.

So long, pushrods. Its bore and stroke combination, 99mm x 93mm, was also new. The result was a high-revving, free-breathing 5.7-liter V-8 that wasn’t the same old 350.
In its developmental stage, this V-8 produced 380 hp at a time when the contemporary Tuned Port Induction L98 Corvette was only managing 245 hp.
When the 1990 ZR-1 debuted it featured a 375-hp version of the LT5 V-8, built by Mercury Marine, but by 1993 it was churning out 405 hp.

That was more than the 8.0-liter Dodge Viper could manage in its first iteration.
Chevrolet abandoned OHC engines for the Corvette when the ZR-1 ended production in 1995, as the LS1-powered C5 was on the horizon and Chevrolet knew that its new pushrod engine platform would be capable of similar output from a smaller, lighter, easier-to-manufacture package.

Indeed, the C5 Z06 eventually produced 405 hp from a 5.7-liter V-8, but there were some Lotus fingerprints left on Corvette. Both the standard LS1 and the Z06’s high-output LS6 have a 99mm bore-just like the LT5.

This development car marks an important moment in the Corvette’s evolutionary timeline.
The ZR-1 was a technological marvel, a truly special machine that represented the Corvette brand well against some of the best-performing, most prestigious cars of the era.
This example is a bit too historically significant to be wrung out like a proper ZR-1 should, but with any luck it will occupy a place of honor in some Corvette fan’s collection.

 

[teamzr1]

They called the prototype “King of the Hill.” In production, the ZR-1 was the Corvette that Chevrolet built to take on the world, and it was every bit the “super ’Vette” that Corvette chief engineer Dave McLellan had hoped for.

The major component was its LT5 engine, a V-8 born of Chevrolet and Lotus engineering and assembled by Mercury Marine. It shared the same 5.7-liter displacement with the base C4’s L98 pushrod engine, but little else.
The quad-cam, 32-valve, 375-hp LT5 was nothing short of exotic, with trick bits like 16 intake runners that fed hemispherical combustion chambers, and a forged rotating assembly swinging 11:1-compression pistons in Nikasil-coated aluminum bores, all the way to 7200 rpm.
These are top-shelf specs even today, but in 1990? The LT5 was a superstar in a sea of warmed-over, malaise-era crap engines rolling out of Detroit.

A special ZF six-speed transmission and taller 3.33:1 gearing helped the ZR-1 reach supercar terminal velocities. Its adjustable FX3 Bilstein suspension, also created with Lotus, was similar to the system Porsche put in the 959.

The ZR-1’s body was widened to tuck in fat 11-inch rear wheels wearing 315/35-17 tires another “holy smokes” concept in 1990.
The numbers 0 to 60 mph in the four-second range and a 180-mph top speed spoke for themselves.
But this greatness wasn’t cheap. In 1990, the ZR-1 option package cost a staggering $27,016 on top of the $31,979 base price of a standard Corvette.
Additional dealer markup meant that paying $100,000 for a new ZR-1 was not unheard of.

That was Ferrari Testarossa and Lamborghini Countach territory.
By 1991, the ZR-1 package price had grown to over $31,000, where it would remain through 1995, the last year of production. In the end, Chevrolet sold 6922 ZR-1s.
Today, while still highly regarded, the C4 ZR-1 has fallen from grace in the market. In fact, they trade for just a small premium over their L98-powered brethren.

The Hagerty Price Guide and recent sales show that, with similar miles, a #2-condition 1991 L98 Vette sells for about $13,000 to $17,000; a 1991 ZR-1 will sell in the $20,000-to-$25,000 range.
Even the 405-hp 1993–95 ZR-1s hover at roughly a $10,000 premium over the base C4s. Essentially, you can buy a whole car today for less than the cost of the option package.

But why?
Some of what’s holding the ZR-1 back stems from the fear of the LT5’s complexity.
Those who know these cars, however, speak highly of the engine’s durability, and examples with 200,000-plus miles on them are out there. Apprehension over parts availability is another factor. Sure, GM no longer stocks LT5 engine parts, but they are not hard to find in the aftermarket.

There are other intricacies to the ZR-1 market, too, such as the divide over what’s more desirable the pre-face-lift first-year 1990 model, with its chiseled front and rear bumpers, or the more rounded 1991–95 cars. Buyers seem to make the argument both ways. But among serious collectors, the age-old factor of mileage reigns supreme.

Most place a high value on extremely low-mileage cars and heavily discount those that have anything beyond a single-digit odometer.
The sweet spot for me would be about 25,000 miles high enough to know the car doesn’t have shelf rot while also getting a good discount from an “in the wrapper” car, and low enough to be able to add a couple thousand miles a year to enjoy it without getting murdered come resale time.

Today’s C8 Corvette shows how far we’ve come from the C4’s chassis and ergonomics, but that LT5 is still so enjoyable that it makes having to climb over the wide sill and into the cramped, plastic-lined cockpit worthwhile.

Which really begs the question as to why values of America’s supercar have remained so flat for so long.

The answer might lie in the fact that more modern machinery and budget-priced C5 Corvettes offer more performance and amenities for less money.
But like everything else on the rise from the 1980s and 1990s,
I do think C4 ZR-1s will soon escape from the “just a used car” syndrome and come into their own.
After all, these were the top dogs in their day, and everything is cyclical.
Add to that the emerging “Radwood effect” we’re seeing with poster cars of this era, and it sure seems like you could do a lot worse than buy the ultimate 1990s Corvette for half of what a new Silverado will cost you.

 

[teamzr1]

From my files,
In 1987 ZR-1 history Jim Ingles prototype testing

 

[teamzr1]

It was a crazy and exciting time back in the mid 1980s and early 1990s, for me included
GM was in a buying binge then and now had Delco, GMAC, Lotus, Hughes Vsat and electronics and the company I was
working for Electronic Data System (EDS) mid 1980s
I was then split into to working on EDS side and GM projects
As a long time Corvette owner, I was thrilled that GM was doing a prototype of a Europe killer sports car
Owning Lotus, they were give a clean sheet of paper to do a design Lotus wanted and only 2 rules
LT-5 had to fit in and bolt to existing C4 frame rails and the spacing between bores of cylinders

Here is makeup of a prototype ZR-1 in 1987 for Jim Ingles to start testing


Was clear by us within GM and also Lotus that the ZR-1 would show the snobs of Europe that America's sports car could break world records and win races away from the Europe sports cars

In the spring of 1990 n Texas the ZR-1 broke several Europe speed and distance records that ZR-1 (now called King of the Hill)
that it would hold onto for some years



Would not stop there as now wanting to prove the ZR-1 could compete and also win races


Was getting a ton of free press from the auto rags and was insulting to Europe how they looked down their noses of American
cars and were not happy about it

But as the worm turns, those in GM engineering hated Lotus as being jealous as they selected to design the LT-5
As designs for the C5 began, there was a war within GM to kill off the ZR-1 and the LT-5 for a new LSx designed engine and these
dirty engineers came up with a scheme to test both engines and see who the engine winner would be, but they sneaked in tests they know the LS engine would win each time

So only was the ZR-1 killed off, but they instructed that all tools and jigs to build the LT-5 be smashed up and cease all LT-5 parts not be in supply chain
Those of us pro ZR-1 were clearly pissed
1 day by mistake
I parked by 1994 ZR-1 right into one of the main entrances of the corp building in Warren MI, locked the doors and went to my testlab
across the street at the Tech center
I was really pissed off


Team Corvette guys laughed their asses off in my doing that and took this photo and below each signed it




GM wanted the #93 and #94 racer ZR-1s either quickly sold off or smashed up

Even after spending $70,000 for the 1994 ZR-1, I wanted to save one of these racers so had to come up with a way
which I did for the sum of $145,000 and bought and raced the #94