C4 CORVETTE ZR-1 : TOO GOOD TO SUCCEED

The C4 generation marks a very important turning point in the Corvette’s life. After the C3 fended for itself for 15 years, the C4 was really the first clean sheet Corvette since the C2 in 1963. There was a new chassis with all-aluminum suspension components, and the steepest windshield rake ever seen on a production car. Unfortunately, under the hood still lay the same 5.7L Gen I Chevy Small Block V8 that had more or less been around for 20 years. It wasn’t until the C4 Corvette ZR-1 showed up in 1990 that the Corvette really began to flourish into the world-beater we know today.

According to Hagerty, during the development phase, one of the design mandates was to make the car more invisible to radar. Because the Corvette’s body is made of fiberglass the first thing that gets pinged is the radiator. That’s why the C4’s rad sits at an angle, it halved the distance a radar gun could see the car, from 3,000 feet to just 1,500.

Fantastic.

Prior to the C4 Corvette ZR-1, the team was playing around with 400 hp twin-turbo versions of the Corvette’s L98. Aside from perpetually breaking transmissions, the final nail in the prototype’s coffin came when a General Motors executive spun one of the development mules off into the bush.

How history repeats itself.

Anyway. Because the Gen I Small Block was running out of breath by this point, Chevy started to look elsewhere for an engine that could compete with top-shelf supercars at the time. Thankfully, in ’86 GM had acquired a majority stake in famed UK engineering and performance car firm, Lotus.

Lotus Engineering began work on an all-new engine that would fit within roughly the same footprint as the 350 already under the hood of the C4. The result was the aluminum 5.7L DOHC LT5 V8. It shared nothing with the L98 save for the bore center measurement, and instead of the typical two-valve cam-in-block setup, there were now four overhead camshafts and four valves per cylinder.

It had a forged crankshaft, lightweight pistons and connecting rods, and a compression ratio of 11:1. When it debuted, the result was a dazzling 375 hp at 6,000 rpm and 370 lb. ft of torque at 4,800 rpm. Before the car was retired those figures would jump to 405 hp and 385 lb.ft.

The engine was so unique GM had to commission Mercury Marine’s MerCruiser division to build the engine due to the company’s experience working with aluminum boat motors. MerCruiser chunked out a special section of their Stillwater, Oklahoma facility where the LT5 was hand-built in clean-room conditions.

As you can imagine all of this added cost.

Eventually dubbed “King of the Hill” the C4 Corvette ZR1 was a 180 mph rocket that could take down the 964 911 Turbo in all the categories that matter. Unfortunately, equipping the C4 Corvette with the ZR-1 package almost doubled its sticker price, equivalent to $127,600 in today’s dollars. Advancements made with the Gen II LT1 small-block and the Grand Sport’s LT4 V8, combined with the ZR-1’s slow sales conspired to end the LT5’s reign atop the GM performance hierarchy.