1990 Chevrolet Corvette ZR-1 - King Again

415 Cubes And 610 Horses Make This'90 ZR-1 A Royal Rush

Chris Endres Mar 1, 2009 0 Comment(s)
Vemp_0903_01_z 1990_chevrolet_corvette_ZR1 Front_view 1/10

Long-suffering Corvette performance enthusiasts had their loyalty tested for most of the '70s and the first half of the '80s. Ever since Big Brother stepped in and pulled the plug on the performance party in Detroit, practically nothing of real interest had rolled off the assembly line. Finally, in 1985, the L98 Tuned Port Injection engine became available. Though not exactly a return to the halcyon days of such fire-breathing mills such as the big-block LS6 454 or the high-revving, solid-lifter LT1 small-block, the TPI proved a capable performer, and when paired with the nimble C4 chassis, it was a giant first step back in the direction of performance.

In the spring of 1988, rumors started swirling about a return to true high performance in the Corvette camp. The car in question was to be called the ZR-1, and it would benefit from an unprecedented engineering effort aimed at elevating the Vette to the status of genuine world-class performer. Though still a high-school student at the time, Houston radiation oncologist Sanjay Mehta knew he wanted a ZR-1 from the moment he saw the first spy photos of the new model. "I sat in study hall, reading car magazines, dreaming of the day I would own one," he says. Word of an engineering collaboration with Lotus certainly piqued his interest, as it did for even the most casual of Corvette observers. As it turned out, the fruits of this project were to be unlike any engine previously installed beneath the car's long composite hood.

Vemp_0903_02_z 1990_chevrolet_corvette_ZR1 LT5_engine 2/10

No turbo, no blower, no joke-this engine makes its power the old-fashioned way: lots of cubes and lots of revs. The big 415 regularly sees 7,500 rpm.

The new engine, dubbed the LT5, shared the same displacement as the familiar small-block 350, but that's where the similarities ended. Based on an aluminum block and cylinder heads, the engine featured four valves per cylinder and four overhead camshafts. The advanced combustion-chamber design allowed an unheard of (for the time) compression ratio of 11:1. The LT5 was so smooth, it was claimed a nickel could be stood on edge on the intake manifold and remain standing while the engine was started.

One of the more ballyhooed features of the new ZR-1 was the "valet key." A separate key inside the cockpit could be switched between normal and performance modes. The idea was to limit unauthorized joy rides in the new super-Vette. The LT5 intake manifold featured separate runners and injectors for each of the sixteen intake valves, two per cylinder. This system was only active during spirited driving, and disabling it with the valet key substantially reduced peak power production.

Vemp_0903_03_z 1990_chevrolet_corvette_ZR1 Wheel 3/10

Sanjay Mehta selected a timeless set of Fikse FM/5 wheels, wrapping them in sticky Nitto rubber.

With all the runners active, though, look out! The LT5 churned out 375 hp at 5,800 rpm and 370 lb-ft of torque at 4,800 rpm. This was enough to hurl the portly (3,520 pounds) ZR-1 through the quarter-mile in 13.4 seconds at 109 mph. All LT5 engines were hand-assembled at the Stillwater, Oklahoma, plant of Mercury Marine before being trucked to Bowling Green for installation in the ZR-1 chassis.

While the engine got the majority of the attention, the ZR-1 chassis was no slouch, either. Featuring the cockpit-adjustable FX3 suspension, it had three settings to allow the driver to maximize the car's performance under different driving conditions.

The car was soon dubbed "King of the Hill" by GM insiders, and the press was quick to adopt the sobriquet. Had Chevy gotten it wrong, this unofficial title could easily have blown up in the company's face. Thankfully, this wasn't the case. Not that many nonenthusiasts noticed. Despite its brawny performance, the ZR-1 wasn't exactly a head-turner.

Vemp_0903_07_z 1990_chevrolet_corvette_ZR1 Rear_view 7/10

The rear fenders are stretched to cover the massive 17x11 wheels and 315/35 tires originally installed by General Motors. A B&B exhaust system ensures the sound is just right.

Besides price tag, this was perhaps the single item most to blame for the ZR-1's lack of showroom success. Though true enthusiasts could pick out the King easily enough, the rest of the world easily missed the subtly widened rear fenders cloaking enormous 315/35-17 Gatorbacks, and the convex rear bumper cover with its rectangular taillights. These visual tip-offs were further diminished for the '91 model year, when the base car received a minor facelift featuring--you guessed it--a convex rear bumper cover and rectangular taillights.

While the ZR-1's unique appearance was quickly diluted by the lesser model, its performance remained unmatched by its less costly sibling up until its demise in 1995. More trouble was on the horizon, however, as the C5 was just around the corner, and with it the promise of more power; less weight; a completely new suspension; an advanced, hydroformed chassis; and slippery new aerodynamics. The ZR-1 remained an impressive package, but its kingdom was quickly becoming a fiefdom, courtesy of the relentless advance of technology.

What Mehta couldn't have imagined all those years ago was just how over-the-top his own ZR-1 would end up being. While a stocker is obviously a very stout performer, even a mildly modified C5 can give it a run for its money. Deciding that only the best would do, Mehta planted a Lingenfelter Performance Engineering stroker under the hood. Sporting a resleeved block, a fully forged rotating assembly, intricately ported cylinder heads, and four more-aggressive camshafts, the LT5 now bristles with 610 hp and 520 lb-ft of torque from a displacement of 415 ci.

Vemp_0903_08_z 1990_chevrolet_corvette_ZR1 Roll_cage 8/10

The rollcage was installed as a safety measure prior to tackling the Texas Mile, where Mehta laid down an impressive 184.55 mph in the standing mile.

Though the original ZF six-speed gearbox remains, a Spec Stage 3 clutch provides rock-solid coupling while keeping the pedal effort reasonable. The remainder of the drivetrain remains stock and has held up admirably to the brute force it is asked to transmit.

Moraca-valved Bilstein coilover shocks retain the adjustability of the FX3 suspension while improving damping. "When performance mode is selected, the car corners perfectly flat," Mehta says. "But in touring mode, the car is very comfortable and has great weight transfer for dragstrip launches. It's really the best of both worlds."

Another area that needed attention due to the increase in power was braking. Mehta selected a set of Wilwood four-piston calipers with 13-inch rotors for the front, but he deemed the stockers sufficient for the rear. Of course, tires are the most vital aspect of grip, whether accelerating, decelerating, or turning. To this end, a distinctive set of Fikse FM/5 wheels were fitted with Nitto rubber, the rears being NT555R Extreme Drags for their extra grip. "The drag radials actually made First and Second gears useful," Mehta quips.

Vemp_0903_09_z 1990_chevrolet_corvette_ZR1 Rear_view 9/10

One could be forgiven for overlooking the subtly flared rear fenders and discreet ZR-1 badge. But if you miss the license plate, you deserve what's coming to you.

Besides the obvious addition of the Fikse wheels and shiny B&B Tri-Flo exhaust tips, most would be hard pressed to distinguish this from just another nice C4. The car still sports its original Dark Red Metallic paint, having been one of just 181 ZR-1s blessed with this color in 1990.

Most cars that look this good seldom leave the garage, but not Mehta's. He has wrung his Vette out in nearly every discipline imaginable. It's seen countless laps at the road course during open-track events. It's been hammered down the quarter-mile to the tune of 11.1 at 129 mph (on street tires, no less). It's even won its class at the Texas Mile, where it posted an amazing 184.55 mph.

Though Mehta doesn't get to drive the ZR-1 as often as he might like these days, it never fails to put a smile on his face. "The interior is like a cocoon, and when you run the tach up to 7,500 rpm in Second gear, there's nothing else like it. No other Corvette can match that feeling."

Yes, it's good to be king.

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