Back before the mighty C6 ZR1 rumbled out of Bowling Green with its supercharged 6.2-liter LS9 V-8 making 638 horsepower and 604 pound-feet of torque, there was a previous king-of-the-hill Corvette that bore the same ZR1 name (though it was hyphenated ZR-1). The C4 ZR-1 saw production from 1990 through 1995 and came with a rather unconventional engine design never before seen powering a Corvette.
The ZR-1’s small-block 350 had dual overhead cams and 32 valves.
Sure, DOHC are a commonplace thing found in engines, but this represented uncharted territory for the Chevy small block that had always used a single cam and pushrods to operate the overhead valves. Luckily, General Motors had acquired Lotus in 1986, and soon after the purchase, engineers with Corvette approached Lotus with their plans of building the world’s fastest production car. Together the UK-based automaker and The General went to work combining the classic V-8 with the modern DOHC design. The result was named the LT5.
Displacing a familiar 5.7-liters, (or 350 cubic inches, depending when you were born) the LT5 engine produced 375 horsepower, which helped push the ZR-1 Vette to 60 in 4.5 seconds and had a top speed of over 180 mph. The power rose to 405 horses when Lotus redesigned the heads and valvetrain for 1993. Those were stellar numbers 20 years ago.
General Motors had one problem, however. They couldn’t handle the extra workload of building the specialized engine. So GM contracted the engines to be built by Mercury Marine,, a company normally associated with boat engines (and no relation to Ford’s Mercury division). Only 6,939 C4 Corvette ZR-1s were ever built, but they created a legend only touched years later by the C6 Corvette ZR1.
As part of Mercury’s 75-year anniversary, the company is remembering this mighty engine, an dhas placed an example on display at its headquartersI.
Click past the jump to read more about the 1990 ZR-1 Corvette Powered By Merc LT5 Engine.
1990 ZR-1 Corvette Powered By Merc LT5 Engine in detail
Why It Matters
To help commemorate the unique LT5 DOHC small block, Mercury Marine is displaying a 1990 Corvette ZR-1 in its headquarters in Stillwater, Oklahoma. The LT5 still remains the only DOHC Chevy small block engine ever produced, making it a highly coveted piece of automotive history. The fact such big names in engine engineering came together to build the LT5 is another testament to collaboration and teamwork.
Maybe the best way to prove technical innovation and manufacturing prowess is to be selected to power an American icon. Such was the case in 1988 when Mercury Marine was chosen to manufacture the LT-5 engine for the 1990 ZR-1 Corvette.
Designed by Lotus Engineering for General Motors, the LT-5 was an all-aluminum 5.7 liter small-block V8 featuring radical 32-valve dual overhead cam heads; it generated 375hp and was hand-built by Mercury’s MerCruiser division in Stillwater, Okla. For the 1993 model year, horsepower was bumped to 405 with cam timing and engine porting changes. Further proof of MerCruiser’s production proficiency occurred when the LT-5 was awarded the automaker’s most demanding quality certification — GP3 Level 1 — the first GM engine ever to earn it.
The LT-5 became the most celebrated Corvette engine of all time, accumulating records along the way. In 1991, a slightly modified ZR-1, with a “bone stock” LT-5, broke three world endurance records at the Firestone test track in Fort Stockton, Texas. A team of drivers headed by Tommy Morrison broke the 24-hour endurance mark set in 1940 by almost 15 miles per hour, traveling 4,221.26 miles at an average speed of 175.885 mph. Two years later, a MerCruiser-branded ZR-1 took the checkered flag in the 24-hour World Challenge race in Mosport, Canada, with another ZR-1 finishing second.
As production of the LT-5 wound down in 1994, ZR-1 owners converged on the Sooner State to pay tribute to those who built the legendary power plant. Seventy owners towed, shipped and drove their ‘Vettes to Oklahoma to participate in a two-day event know as “Thunder in Stillwater.” Festivities began with the visitors escorting the homecoming court and cheerleaders to the local football stadium for the big game. Plant tours followed, during which the owners shook hands with the men and women of the LT-5 production line. The cars were then driven to Oklahoma State University and arranged on the football field to spell out LT-5.
It was a bittersweet moment for all, but one they will never forget.