1984 -1996 Chevrolet Corvette C4 - Generation-Four Spotter's Guide

1990
What You See:
This was the first year for the ZR-1. The special ZR-1 LT5 engine was designed by Lotus and built by Mercury Marine. The exotic four overhead cam engine burst on the Corvette scene, producing 385 hp. A hybrid digital/analog dash was installed in the '90 Corvettes, featuring a digital speedometer with an analog tach and secondary gauges.

1991
What You See:
The big news for '91 was the updating of the front and rear (non-ZR-1) fascias. The more rounded front featured wrap-around lights, and the body side molding was painted the body color.
What You Don't See:
FX3 and Z51 were combined to make a new RPO Z07 featuring selective ride control with the performance-handling package. RPO Z07 was designed for aggressive driving or competition, and adjusted the ride from firm to very firm. Also, an oil-pan float was installed to alert the driver of a low oil condition. This was also the first time that delayed power was installed in a Corvette, allowing the occupants to listen to the radio or operate windows after the key was turned off. This was also the last year that Callaway B2K Corvettes were available.

1992
What You See:
The big news for Corvette in 1992 was the introduction of the second-generation small-block, dubbed the LT1. This new offering was under the direction of Anil Kulkarni and focused on cooling issues as well as improved fuel/air control.
What You Don't See:
The LT1 produced 20 percent more power, had better fuel mileage, and met emissions standards better than the L98 (Tuned Port engines). Along with the new engine, synthetic oils were introduced which eliminated a need for any oil coolers. Automatic Slip Regulation made its way into Corvette in '92 as a standard feature. The one-millionth Corvette was built as a '92 model.

1994
What You See:
The National Corvette Museum opened in 1994. Two new colors were added-Admiral Blue and Copper Metallic-with only 116 Copper Metallic Corvettes produced before the color was discontinued. ZR-1s went to a non-directional wheel unique to ZR-1 Corvettes.
What You Don't See:
A new sequential fuel-injection system was introduced that injected fuel to only the cylinder that needed it instead of firing an entire bank of cylinders in a batch. The transmission also received electronic upgrades. Instead of relying on a throttle-valve cable to regulate fluid pressures inside the transmission, electronic solenoids were used which gave more control to the operation of the shifting characteristics of the trans. Corvette owners would be required to step on the brake before shifting out of Park.

1993
What You See:
Corvette was back celebrating anniversaries on even numbers again, and this year was its 40th. A special Ruby Red Anniversary Edition was available in all models, and all leather seats installed in Corvettes for '93 had "40th Anniversary" embroidered into the headrests. The '93 Corvette was the first auto sold by GM to utilize a passive keyless entry (PKE) system.
What You Don't See:
The LT1's engine noise was made quieter by changing to a composite valve cover instead of the earlier metal covers and insulating it better from the rest of the engine. Also, the exhaust-valve closing velocity was reduced through camshaft lobe modification. Horsepower remained at 300, but torque increased another 10 lb-ft as a result of cam reconfiguration.

Mandatory Reading For C4s
The C4 Corvette Sourcebook, by John LoughmillerThe Heart Of The Beast, by Anthony YoungHow To Understand, Service and Modify Corvette Fuel Injection & Electric Engine Management, by Charles O. ProbstCorvette From The Inside, by Dave McLellan

1996
What You See:
GM wanted to protect the last year of C4 production numbers so it offered several different editions to help grab customers who might wait until the next year's C5 was offered. Grand Sports and Collector Editions, as well as the other models, were available with the updated LT engine: the LT4. With redesigned heads, camshaft, intake, and roller rockers, this engine was capable of cranking out 330 hp instead of the LT1's 300. The LT4 was only available with a standard transmission, and all Grand Sports came equipped with the LT4.
What You Don't See:
Electronic control took on a larger role for the '96 production year. The suspension RPO FX3 was dropped and replaced with F45. The difference between the two suspensions was that FX3 adjusted all four shocks simultaneously, whereas F45 adjusted each shock individually every 10-15 milliseconds, which equates to approximately every foot of road surface at 60 mph. Also, due to the computer's increased role in engine/transmission/suspension management, the number of identification codes to identify a problem increased from 60 to 140. Once again, Corvette regained the top spot in AutoWeek's annual subscriber survey of American cars (July 1, '96) in which readers had the most pride. It pushed Viper into second place.
In a short 12 years, Corvette has progressed from a great-performing sports car, reeling in accolades using only the most basic of electronic computer technology, to a refined canyon carver, producing historic amounts of horsepower and performance using technology that dwarfs its predecessor by light-years. Horsepower was back and it was clear that GM wasn't going to be deterred from installing as much as possible in every Corvette. Of course, it had to be emissions-friendly as well a great performer, which it grew into. The forward thinking that went into the C4 improved the current Corvette, but also laid a foundation, the benefits of which would be reaped well into the next generation.So the next time a C5 owner tells you how great their car is, just say "You're welcome."

1995
What You See:
Corvette was pacing the Indy 500 again and GM offered a dark purple and white Pace Car to commemorate the occasion.
What You Don't See:
This would be the last year for the ZR-1. The dash in '95 Corvettes was improved by providing better mounting of the CD player to prevent skipping. Several Velcro(r) strips were included under the dash assembly to eliminate squeaks and rattles. All '95 Corvettes received the upgraded antilock/traction-control system as well as the larger brakes previously installed only on ZR-1s.