It’s difficult to overstate the significance of the C4 ZR-1 upon its introduction. In the years leading up to it, rumors swirled and grainy spy phots of a royally dubbed “King of the Hill” high-performance variant captured the imagination of countless enthusiasts. At a time when any new vehicle with more than 250 horsepower was virtually guaranteed the cover of an automotive magazine, this first-ever Corvette supercar promised to be a game changer.
When its extra-wide 315/35ZR17 Goodyear Eagle ZR rear tires finally lit up the pavement in 1990, the ZR-1’s exotic LT5 DOHC V-8 was hailed as a marvel of mechanical achievement, and its 375-horsepower output equaled that of the Ferrari Testarossa’s V-12. The engine was famously developed in a joint venture between Chevrolet and Lotus, and assembled by marine-engine manufacturer MerCruiser.
Chevrolet indeed made a statement that its flagship performer could run with the world’s best. Everyone agreed. Unfortunately, they didn’t exactly acknowledge it with their wallets. Despite an initial stampede for the first few cars off the line, demand for the roughly $30,000 ZR-1 option—applied on top of the $32-$37K tab (depending on model year) for a base C4 coupe—quickly waned.
Sales peaked in the first year at 3,049 and dropped by a third the following year, when all Corvettes received a convex rear fascia that had previously been exclusive to the ZR-1. The loss of a unique visual identity further suppressed sales, as many came to view the ZR-1 as nothing more than a very expensive engine option. Sales dropped to 502 in 1992 and were metered by Chevrolet thereafter, with 448 built in each of the car’s three remaining model years. It was a lamentable end to a project with the grandest ambitions.
During the ZR-1’s production run, the horsepower rating was increased from 375 to 405 hp, thanks mostly to camshaft, cylinder-head and valvetrain revisions. That’s no secret. But what most enthusiasts don’t know is that there were plans for another updated LT5 waiting when the decision was made to discontinue the ZR-1—one targeted at 475 naturally aspirated horses and originally scheduled for the 1995 model year.
Graham Behan was an engineer who joined Lotus a couple years after the LT5 project began secretly in the mid-1980s. He was eventually charged with overseeing the enhancements for the 405-hp “Gen II” LT5 used in the 1993-’95 cars. Along with head and cam improvements, the blocks of those engines were also strengthened, in part through the use of four-bolt main-bearing caps. Such continual improvement pushed Lotus into the development of the Gen III LT5, again with Behan at the helm, but Chevrolet pulled out the rug before the first prototype could be assembled.
“It was disappointing when the end came, because there was so much potential in the basic design,” says Behan. “We had a team of young, eager and dedicated individuals who gave the maximum effort to bring the LT5 to life—and we felt there was more to do with it.”