Few Corvettes in history were as anticipated as the ZR-1. It was no secret that GM needed more horses for its Corvette if it was to be competitive in an increasingly powerful marketplace. The standard 350 engine had been starved down to 165 hp in 1975 and had only been improved to 240 hp by 1989. The future of the marque was dependent upon adding performance or it would surely die. Luckily, GM decided to save the Corvette. It may not have anticipated the difficulty of this task at inception, but the finished product brought pride back to the Corvette name.
Concept and development
The initial thoughts for the new powerplant were to keep the internal camshaft and two valves per cylinder and turbocharge for added ponies. These configurations didn’t work out, and project engineers decided to use overhead camshafts and multiple valves, much like the European competition. GM’s Lotus plant in Hethel, England, had expertise in this type of engine development, so they were tapped to develop the new “King of the Hill” engine for the Corvette.
Designing the new overhead cam heads and intake proved to be just the beginning of this task. The normal assembly line procedure was to place the engine into the Corvette from the bottom. But with the stock engine block and the new dual overhead cam heads bolted on, the engine was too wide to fit in the car from the bottom. The possible solutions were all expensive and complicated, so GM decided to build a completely new engine. It needed to have the reliability of the cast iron block, but be as light as possible. The answer was a block casting made of a new lightweight aluminum alloy that was narrow enough to be inserted from the bottom between the frame rails of the car. The new Corvette needed to have the performance and handling of an exotic car such as the Countach, without the scoops and wings. It also needed to be more reliable, civilized, and much less expensive.
The ZR-1’s new engine was to be manufactured by Mercury Marine, at Stillwater, Oklahoma. The production schedule called for about 18 engines per day, and the company had good quality control history.
DOHC and four valves per cylinder
The new engine was designated the LT5 and featured four overhead camshafts and four valves per cylinder, with multi-port fuel injection. The compression ratio was 11:1 with an initial 375 horsepower on tap.
The ZR-1 was available in coupe form only, and while it did not stand out from the standard Corvette at first glance, the changes were more than skin deep. The new Corvette had a bulging rear fascia and square taillights as opposed to the concave rear and round lights on the stock Corvette. A small ZR-1 emblem was affixed below the right taillight. To accommodate the new horsepower, the wheels were upgraded to eleven inches wide with Z-rated 17-inch rubber. To fit the tires, the rear of the car was widened by three inches. This meant special panels for the rear clip, rocker panels, and doors.
The ZR-1 was only available with the 6-speed transmission. A unique feature was the “Valet Key,” which enabled the driver to switch between power mode and normal mode. Normal mode disabled the secondary intake ports and limited the horsepower to around 200. Each time the ignition was switched off the “normal” mode was automatically selected. When manually switched to power mode, the full 375 horses were unleashed.
Double the price of a Corvette?
In 1990 the base price of a Corvette coupe was $31,979, and the ZR1 option added $27,016 to that price. To be fair, the ZR1 package also included power leather seats, selective ride and handling, Bose stereo with CD changer, and a low-tire-pressure indicator that would have added up to $4,829 on a base model. So let’s rationalize the ZR1 option to be only an additional $22,187.
With a few options, it was easy to exceed $60,000 for a Corvette. Despite this, there was no sticker shock dissuading the first buyers. When the ZR-1 was introduced in 1990, some buyers wrote checks for six figures to be among the first to own the new ZR-1. Dealer price gouging was the norm.
From 1991 to 1993, the ZR1 option increased to $31,683, though in 1994–95, it dropped to $31,258. The only change was an increase to 405 hp from 1993 to 1995, accomplished by intake and valve changes.
There were 3,049 ZR-1s built in 1990, 2,044 in 1991, 502 for 1992, and 448 in each of the remaining three years, for a total of 6,939. The reasons for the declining demand are numerous, but the price became a major factor.
Coupled with that was the fact that the standard Corvette LT1 engine offered 300 hp in 1992 and the power gap between LT1 and ZR-1 was closing, which made the dollars-per-horsepower curve less desirable.
Also, the square taillights and convex rear fascia were extended to the total Corvette line, which completely devalued the ZR-1’s signature and left it visually different only by its high center-mounted brake light and small emblems.
Step on the gas and wipe that tear away
There is no doubt that, when first introduced, the ZR-1 option gave this Corvette a major performance advantage over other production cars on the road. Numerous magazine road tests were conducted over the five-year span of production and I was able to find a quarter-mile time in the high 12s to low 13s at speeds from 105 mph to 113 mph. Zero to 60 mph came in the 4-second range. That’s significant bang for the buck.
What’s the future for the ZR-1 market?
A fair number of ZR-1s were purchased and then immediately thrashed and raced to death by those who could afford them and had the need for speed. We also know that quite a number of these cars were simply put away for speculation and in the hopes of reaping a windfall profit. There are several problems with this approach.
Let’s say approximately half of all ZR-1s were put away and kept in pristine, low-mileage condition. That means there are over 3,000 cars to choose from, which means there are just too many out there for the values to go up significantly. In short, the long-term odds on ZR-1s being anything more than desirable used cars are very slim.
The market bears this out on a daily basis. Numerous ZR-1s with under 10,000 miles on them sell in the $30,000-range. We see a few selling for a bit more and some for a lot less, but those are either exceptional or thrashed.
I don’t see prices dropping much in the future, although anything is possible with new Corvettes promising 600 hp and better ergonomics and technology than the ZR-1. Interesting as it is, the ZR-1 is getting dated by today’s standards and it’s just not stylish enough to compete with a ’67 Sting Ray in the eye candy department.
Damn. Should I just buy one anyway?
That depends on that age-old question. Why do you want a ZR-1? What will you do with it? What’s its mission?
1. Do you want to just drive a lot and enjoy it?
If you can put up with some difficulty in the entry-exit contortions and you aren’t averse to rattles and shakes in the dashboard and other places, then this is the car for you. It’s fast, more reliable than anything else in its class and era, and the price is not likely to drop much lower, so the cost of enjoying it should be minimal.
2. Do you want everyone to watch you drive by and say “Wow!”?
Sorry, they won’t. The ZR-1 looks too much like any other used Corvette to draw much attention. That was a big part of its problem. People who spend almost double the price of the base model do not want it to look like the base model.
3. Do you want it to put it away without driving it, as an investment?
Forget it. You will have to keep it at least 20 years, and by then you will need that money for the kid’s college fund. The chance of bettering returns in most other investment areas is slim. Also, if you don’t drive it, the seals and gaskets will wear out and you will have to recondition it prior to using it anyway.
ZR-1 problems and recalls (there were some)
There were a few recalls and numerous service bulletins on the ZR-1. But there were no more than any other car in this category, and most of the fixes weren’t terribly expensive. The windshields tended to show distortion and delamination. The ZR-1 windshield was special to the model and it may be difficult to find an original. There are rumors of oil leaks and brake master cylinders going bad, but again, these generally aren’t too costly. Parts will undoubtedly become more difficult to come across as time goes by, and I believe GM sold most after ten years.
OK, I want one, what do I watch out for?
As I said, there aren’t many things specific to the ZR-1 that are unusually problematic. The usual areas of paint and prior accident damage should always be of concern and can present some very expensive problems. Look as you would at any other Corvette or even another used car. Most ZR-1s have been well cared-for, and abused ones should stand out and be avoided no matter how cheap. Make sure the VIN shows the car to be a true ZR-1. The ZR1 option will have a “Z” as the fifth digit where a standard model will have a “Y”. I have seen standard Corvettes with the LS5 engines installed.
Call the ZR-1 a moral victory, at least
With the amount of research and development needed to bring this car to market and a strict cost vs. profit analysis, I’d say the ZR-1 project was not a rousing success. Sales dropped significantly after the initial impact and the option only lasted five years. Initially, the engine recalls were shipped back to Mercury Marine, but after that contract ran out, local dealerships must have had nightmares dealing with this engine, which was unlike anything else in their inventory. Body and powertrain parts were specific to this model and stocking inventory had to eat into any profit quickly.
Success isn’t always just dollars, though. The ZR-1 gave General Motors excitement, an enthusiasm that ran across its entire product line. It provided immeasurable free publicity in print and video and gave them a badly needed new halo car.
Most enthusiasts who stopped in at their dealer would not purchase a ZR-1, but they might buy a standard Corvette, Malibu, or Caprice. Getting them into the store is what selling is all about, and it costs money to do that. The ZR-1 offered excitement and enthusiasm when Corvette sales were otherwise marginal, and that makes it a success in my book, even if it might not have been a favorite among the GM bean counters.