Despite the economic prosperity of the fifties and the early sixties, there had been a great many who believed that the sustainability of such financial growth was impossible and that more challenging financial times lay ahead within the United States, and even globally. The arrival of the 1968 Corvette occurred at a time when the world, much like the Corvette itself, was struggling to find an identity of its own amidst political, social and financial turbulence.
For its own part, General Motors had recognized that skyrocketing gas prices and performance-car insurance premiums coupled with spiraling inflation made purchasing and owning a Corvette increasingly expensive for future consumers.
It was from these beliefs that GM had settled on redesigning only the exterior of their extremely popular sports car, utilizing the structural and mechanical aspects of the second-generation Corvette in lieu of allowing engineers to fully re-envision it from the ground up. After all, GM had spent a fortune developing the Sting Ray, and yet it had been doomed to a short life – an indirect (though intentional) result of the even earlier first-generation C1’s decade-long production run.
Still, the Sting Ray’s development had cost GM a fortune, and there was no way that they were going to repeat that expensive process just four years into the production run of the C2. Instead, the management at General Motors had hoped that Duntov, Mitchell, and the team behind Corvette could develop a new design that would top (literally) the current Sting Ray.
Further, given the lagging sales numbers of the C2, Chevrolet had hoped that a sexy new exterior that showcased the high-performance engines and drivetrains of the C2 Corvette would be enough to keep the sales numbers of the car on an upward climb.
As much as General Motors tried to keep the new design of the 1968 Corvette a secret, the unveiling of the new body style would actually take place a few weeks before the car was officially unveiled to the public.
Just before the 1968 Corvette was to be introduced, toy manufacturer Mattel™ had released its new line of Hot Wheels™ and, much to the surprise of General Motors Executives, introduced an unauthorized version of a car called the ‘Custom Corvette’ which closely resembled the (as-yet) unveiled Corvette.
The irony behind the 1968 Corvette’s unveiling is that the third-generation Corvette was actually supposed to have been introduced a full year earlier – in 1967.
The reasoning behind delaying its introduction had been as much a financial decision as anything, though critics would actually use the delay as a further opportunity to lash out at the car when it did finally arrive. The reality, however, is that sales of the 1967 model had dipped considerably – from 27,720 Corvettes in 1966 to a disappointing 22,940 in 1967. It had been believed (and hoped) that delaying the Corvette’s release would increase the anticipation of the new model’s arrival for potential customers.
Beyond the lagging sales numbers of the 1967 C2 Corvette, the C3 had also suffered developmental problems which had prevented the possibility of an earlier unveiling. Prototypes of the new car had showed an alarming tendency to lift under acceleration.
This item was resolved by cutting vents in the front fenders and by increasing the spring rates. Also, due to the “wasp-waisted” (so named for the narrowing of the body between the front and rear axles) body design, the passenger compartment was narrow and cramped. Additionally, the low roofline restricted both driver and passenger headroom.
Despite all of these items, the manufacturing challenges (and the subsequent delays they caused) was not entirely a bad thing. The Federal government had issued the first ever safety and emissions standards, with the implementation of these standards to begin with the 1968 model year.
Chevrolet would have seen to it that their next generation Corvette was built to these standards, but by delaying the introduction of the new Corvette until 1968, Chevrolet’s engineers were instead able to focus some of their attention on the five other higher-selling model lines in the 1967-68 Chevrolet fleet.
The new Corvette did feature many aspects of the beloved second-generation Corvette, including engine and powertrains that were retained from the previous year.
The Turbo Hydra-Matic, which replaced the optional two-speed Powerglide Transmission, was a far superior option to what had been available to consumers just the year before.
In addition to its factory default option, the 1968 Corvette offered no less than six optional engines to consumers. The output of these engines ranged from the standard, factory installed, somewhat conservative 300 horsepower, 327 cubic inch small block (which was mated to a three-speed manual gearbox,) to the earth-shaking, high output 435 horsepower, 427 cubic inch, big-block L71 V8 engine.
In between these two extremes, the lineup included the L79 327 cubic inch small block which was rated at 350 horsepower. Next came the 427 big blocks: the 390 horsepower L36 engine, and its triple-carbureted stablemates, the 400 horsepower L68 (and the aforementioned L71 engine.)
Topping things off were the L88 and the L89 aluminum-head packages for the L71. While some critics claimed that the later of these engines was “too brutish a beast”, the small-block V8’s did offer consumers enough power to satisfy most appetites for high-end speed and quick, off-the-line acceleration. All-in-all, the new 1968 Corvette received high marks for its straight-line performance. Of course, these “new” engines (and the corresponding factory drivetrain that came standard with them) were carryovers from the previous year.
All of the 427 cubic inch engines (with the exception of the L88) were fitted with new low-rise intake manifolds that had been designed to allow the carburetor (or carburetors) adequate clearance beneath the third-generation Corvette’s low-sitting hood.
Efficient intake flow was ensured and protected by sinking the manifold’s underside into the big block’s lifter valley. For its own part, the 1968 L88 427 engine included the addition of smog controls, which included a PCV valve and Chevrolet’s air injection reaction (AIR) system.
Similarly, both the Muncie four-speed manual transmission and the aforementioned Turbo Hydra-Matic also received praise from critics and enthusiasts alike. However, there was still some criticism about how the power transfer to the rear wheels affected the drivability of the car.
When it came to handling, the critics noted that while they liked the skidpad and slalom numbers that the new Corvette was produced, they did not like the way the car felt when generating them. The new Corvette had a harsher ride than its predecessor, a fact that did not go unnoticed by the automotive press.
The car had a tendency to understeer, (a regrettably recognizable trait of the early-generation Corvettes,) which was a direct result of installing stiffer rear springs to reduce front end lift during acceleration. The rear roll center was also lowered, which, when coupled with the suspension tuning, further added to the understeering issue.
Still, when combined with the decision to fit the 1968 Corvette with wider (7 inch) wheels and low-profile F70 x15 tires, it served to increase the car’s cornering limit from 0.75g to 0.84g, allowing the Corvette to hug the pavement even better than the Sting Ray had. These modifications to the suspension were so well conceived that even Road & Track’s staunchest critics reported favorably about it: “No question about it, the Corvette is one of the best-handling,front-engine production cars in the world.”
Elsewhere on the car, changes had been made to further help distribute weight more evenly or to improve on drivability.
The C3’s battery was relocated behind the seats which also provided additional room under the hood. The second-generation Corvette’s side vent windows were eliminated in favor of a new fresh-air “Astro Ventilation” system. The Astro Ventilation system routed fresh moving air in through the front cowl, around the interior airspace, and out through grilles located in the rear deck right behind the back window.
For maximum ventilation, the rear window could also be removed. Shoulder belts were introduced in 1968 as a “no-cost” option for all Corvette coupes (although the option remained an additional expense on convertible models.) Additional new features for the 1968 model year included an electric rear-window defroster, speed warning indicator, AM/FM stereo radio, and a high-tech, futuristic fiber-optic light monitoring system.
The 1968 Corvette sat lower than its predecessor had. It was also longer, wider, and heavier. The overall length of the new Corvette increased from 175 inches to 182 inches, and most of this was the direct result of the greatly increased overhanging nose assembly at the front of the car. In fact, the wheelbase remained unaltered from the Sting Ray’s 98 inches. The track width increased at both the front and rear of the car, from 56.5 inches to 58.7 inches in the front and from 57.0 inches to 59.4 inches in the rear. Its weight had increased by nearly 200 pounds over the 1967 Sting Ray, so that the new Corvette now weighed approximately 3,400 pounds.
The interior of the car also received a fair amount of scrutiny and criticism. While the car’s body was physically larger than its predecessor, the cockpit had less room in it. This had been the direct result of a decrease in the 1968 Corvette’s overall height from the 1967 model – a reduction from 49.6 inches to 47.8 inches.
Because of this height reduction, it had been necessary to tilt both the driver and passenger seats back, increasing their fixed angle from 25 to 33 degrees. This was done intentionally to account for the car’s low roofline. Unfortunately, adjusting the seat angles had an adverse effect on the Corvette’s occupants: it not only caused discomfort for both the driver and the passenger, but it also meant that both were continually sliding forward during vehicle operation.
Beyond the general aesthetics of the car, the critics also felt that the Corvette’s fit and finish was sorely lacking. They gave the car low marks on a number of items: it lacked luggage space, its ride was harsh, it was awkward to get into and out of, the vehicle’s interior ventilation system was sorely lacking, the concealed windshield wipers worked intermittently, the cockpit was noisy, and the dashboard instrument panel was poorly laid out. Even the newly introduced T-tops, which incorporated a central brace in an attempt to reduce body shake, were prone to leaking during wet driving conditions. Overall, the car’s overall build quality was generally judged as “abysmal.” Car & Driver Magazine returned their initial test car to Chevrolet, saying that the 1968 Corvette was “unfit to road test.”
Despite the critics many negative comments, the 1968 Corvette received much acclaim from Corvette owners and enthusiasts. The poor reviews did not bother the masses, and why should they? Despite its flaws, the new Corvette was still an exhilarating car, giving owners a thrilling driving experience that was every bit as impressive as any Corvette that had come before it. The car produced plenty of power regardless of engine choice, and its all-independent suspension afforded drivers better than expected handling. Even acknowledging that the third-generation Corvette was not “state of the art”, it was generally accepted by enthusiasts as being more than satisfactory.
While testing a 350-bhp 327 roadster with the four-speed transmission and a 3.70:1 final drive, Road & Track Magazine reported that the new Corvette achieved a top speed of 128 miles per hour, a standing quarter-mile of 15.6 seconds at 92 miles per hour, and a 0-60mph time of 7.7 seconds. By contrast, Car & Driver Magazine tested a 400-bhp 427 coupe, which achieved a 0-60 mph time of just 5.7 seconds and a 14.1-second quarter mile at a speed of 102 miles per hour. Naturally, fuel economy suffered as drivers selected larger engines, with the big-block Corvettes getting a mere 11-15 miles per gallon which, when utilizing the standard 20-gallon fuel tank, gave the new Corvette a total range of just 220-300 miles per tank.
Yet, despite the poor reviews and the laundry list of mechanical and structural issues surrounding the new car, more people purchased a Corvette in 1968 than ever before.
In fact, model year sales set a new record at 28,566 units, which was up approximately 5,000 units from the final Sting Ray. Part of the Corvette’s renewed popularity likely had something to do with the highly competitive pricing that GM implemented – a mere $4,320 for a convertible and $4,663 for the coupe.
Ultimately though, the comments written in the May, 1968 edition of Car and Driver perhaps best summed up what made the new third-generation Corvette desirable to consumers: “The Corvette is not a copy of anything. It produces a whole new set of emotions in its beholders. It’s American and no other description begins to capture it. It’s big and why not? America has always demanded big cars — we’ve got plenty of space. Mechanically it feels unbreakable and it delivers a full measure of performance that its competitors can’t match at double the price. Handling is impeccable, limited only by street tires, and the Corvette’s pitch and float-free ride is ideally suited to high speed touring on American highways.”
Type and Description: Independent, SLA type, coil springs with center mounted shock absorbers, spherical joint steering knuckle pivots.
Front Coil Springs
Make & Type
Right-hand Helix Variable rate
Spring Rate (lb. per in.)
Rate at Wheel (lb. per in.)
Design Load at Spring
9.99 in. @ 1395 lbs. (9.99 in. @ 1540 lbs.
Front Stabilizer Bar
Hot rolled steel
.750 with 327ci engine, .9375 with 427ci engine
Suspension – Back
Type and Description: Full Independent rear suspension with frame-anchored differential unit. Position of each wheel established by three links: tubular axle drive shafts, transverse strut rods, torque control arms. Vertical suspension loads taken by transverse leaf springs. Built-in camber adjustment at strut rod inner ends.
Rear Leaf Springs
Number of Leaves
Chrome carbon steel
Length, width, height
46.36 x 2.25 x 2.121
Rear Shock Absorbers:
Direct, double-acting, hydraulic
Caliper Disk – 4 Wheel Hydraulic
Delco-Moraine Vacuum Assisted Powered Brakes
Drum diameter, front (in.):
11.75 x 1.25
Drum diameter, rear (in.):
11.75 x 1.25
Swept Drum Area Effective area:
Wheels & Tires
Wheels & Tires Specs
Short spoke spider, welded steel
Ribbed integral casting, aluminum, quick take-off
15″ x 7.00
F70 x 15 — 4 PR. 2-Ply Tubeless Rayon
F70 x 15 — 4 PR, 2-Ply Red Stripe Nylon
F70 x 15 — 4 PR, 2-Ply White Stripe Nylon
Semi-reversible, recirculating ball and nut steering gear with three-inch axial column adjustment; two-location steering arm-tie rod connection for street and fast ratio. Telescoping shaft steering available optionally.
Location: All engines are stamped on the top front of the right-hand bank of cylinder and case.
F – Engine build location. F – Flint Michigan.
1210 – Date Code. Month and Day. 1210 – December 10.
HE – Type Designation. HE – Regular engine, 3 or 4 speed, 4-bbl. carb.
(Refer to the Engine Suffix section of the 1968 Corvette Specification Page for a list of all Type Designations.)
All engines are stamped on the top front of the right-hand bank of cylinder and case.
1968 Corvette Transmission Identification
Manual Transmission – Stamped on right-hand side of case in the upper forward corner.
Turbo Hydra-matic Automatic – Name plate tag on right-hand side of case.
RJ – Type Designation. RJ – 3-Speed.
S – Source Designation.
S – Saginaw.
R – Saginaw
P – Muncie
CC – Ypsilanti
8 – Model Year. 8 – 1968
EO1D – Production Month and Date.
E – Designates Month
A – Jan.B – Feb.C – Mar.D – Apr.E – MayH – JuneK – JulyM – Aug.P – Sep. R – Oct. S – Nov.T – Dec.
O1 – Designates Day of the month.
D – D or N after the date code designates day or night shift.
1968 Corvette Axle Identification
Location: Bottom left or right of axis tube adjacent to carrier housing. Example: AK0212W
AK – Type Designation. AK -3.36 axle ratio, 3-Speed or 4-speed transmission.
(Refer to the Axle Identification section of the 1968 Corvette Specification Page for a list of all Type Designations.)
0212 – Date Code. Month and Day. 0212 – February 12.
W – Source Designation.
G – Gear and Axle
B – Buffalo
W – Warren
1968 Corvette Factory Options
Base Corvette Sport Coupe
Base Corvette Convertible
Genuine Leather Seats
Soft Ray Tinted Glass, All Windows
Soft Ray Tinted Glass, Windshield
Custom Shoulder Belts (std. with coupes)
Auxiliary Hardtop (for convertibles)
Vinyl Covering (for auxiliary hardtop)
Rear Window Defroster
Special Front and Rear Suspension
Positraction Rear Axle, all ratios
Special Heavy Duty Brakes
Transistor Ignition System
427 Cubic Inches, 390 Horsepower Engine
427 Cubic Inches, 400 Horsepower Engine
427 Cubic Inches, 435 Horsepower Engine
327 Cubic Inches, 250 Horsepower Engine
427 Cubic Inches, 430 Horsepower Engine
Aluminum Cylinder Heads with L71
4-Speed Manual Transmission
4-Speed Manual Transmission, close ratio
4-Speed Manual Transmission, close ratio, heavy-duty
Turbo Hydra-Matic Automatic Transmission
Off Road Exhaust System
Telescopic Steering Column
Bright Metal Wheel Cover
Red Stripe Tires, F70x15, nylon
White Stripe Tires, F70x15, nylon
Speed Warning Indicator
AM-FM Radio, stereo
Base Corvette Sport Coupe (19437)
The base price of the 1968 Chevrolet Corvette Coupe without any optional equipment.
A 327 cubic inch, 300 horsepower engine, a 3-speed manual transmission, and vinyl interior trim was included in the base price.
The 1968 Corvette wheelbase remained the same as the 1967 Corvette, and much of the former car’s chassis carried over, but the interior and exteriors were extensively redesigned. Coupes featured removable roof T-tops and removable rear window.
Hidden headlights were operated by vacuum and raised/lowered into position, rather than being rotated electrically as they had been with the 1963-1967 models.
A light monitoring system was standard and utilized fiber optics to display functioning lamps on a central console display.
The 1968’s door opening mechanism, a spring-loaded finger plate and separate release button, was unique to the year.
Base Corvette Convertible (19467)
The base price of the 1968 Corvette Convertible without any optional equipment.
A 327 cubic inch, 300 horsepower engine, a 3-speed manual transmission, vinyl interior trim, and a convertible soft top was included in the base price.
The 1968 Corvette wheelbase remained the same as the 1967 Corvette, and much of the former car’s chassis carried over, but the interior and exteriors were extensively redesigned.
Hidden headlights were operated by vacuum and raised/lowered into position, rather than being rotated electrically as they had been with the 1963-1967 models.
A light monitoring system was standard and utilized fiber optics to display functioning lamps on a central console display.
The 1968’s door opening mechanism, a spring-loaded finger plate and separate release button, was unique to the year.
Genuine Leather Seats
Optional leather upgrade to replace the standard vinyl seats on the 1968 Corvette.
Soft Ray Tinted Glass, All Windows (A01)
Window tint applied to the upper portion of the windshield and all other windows.
Soft Ray Tinted Glass, Windshield (A02)
Factory window tint applied to the windshield only.
Power Windows (A31)
Factory installed power driver and passenger windows.
A head restraint attached to the top of the seat for both safety and comfort.
Custom Shoulder Belts (std with coupe) (A85)
An addition to the standard lap safety belt that crosses over the shoulder for added safety.
The shoulder belts option were included with all Corvette coupes at no additional charge. The option was also available on the Corvette convertible, but at an additional cost.
Auxiliary Hardtop (for convertibles) (C07)
An optional hard-top that could be installed in lieu of the convertible top.
Vinyl Covering (for Auxiliary Hardtop) (C08)
This option provided an external vinyl liner application to the auxiliary hardtop.
The vinyl covering provided a faux convertible top appearance even when the hardtop was mounted on the car.
Rear Window Defroster (C50)
Deletion of the factory installed heater and defroster.
Air Conditioning (C60)
Factory installed air-conditioning.
Heater integrated, manually controlled by knobs on instrument control panel that operate bowden cables to activate various doors/ducts and switches to operate system.
System includes evaporator, blower, condenser, receiver-dehydrator, refrigerant (freon) tank, air intake assembly and duct assembly for both systems.
Special Front and Rear Suspension (F41)
An optional suspension with upgraded springs, shock absorbers, & stabilizer bar.
Consisted of special heavy-duty coil springs on the front end, with heavy duty shocks on both the front an rear on the car, and a heavy duty 7-leaf rear spring. This suspension package allowed Corvettes fitted with this option to sit slightly lower than the factory suspension.
Positraction Rear Axle, all ratios (G81)
The factory optioned rear axles available for the 1968 Corvette.
The available axle ratios included: 3.08:1, 3.36:1, 3.55:1, 3.70:1, 4.11:1, 4.56:1.
Power Brakes (J50)
Vacuum power assisted brakes; includes dual circuit master cylinder.
Special Heavy Duty Brakes (J56)
Heavy-duty braking system for improved stopping performance.
Consisted of a special proportioning valve which placed the maximum braking effect at the front wheels (in order to compensate for weight transfer under heavy braking conditions), and brake shoes with increased structural rigidity and retention.
Transistor Ignition System (K66)
Deltronic ignition system by Delco -Remy
This was the standard transistorized ignition that was used on the L71 and L89 equipped Corvettes.
This system yields higher spark plug voltage, and operates at extremely high speeds without losing ignition performance.
An added benefit is that the transistor ignition system is essentially maintenance free.
427ci, 390hp Engine (L36)
Alternate engine with improved 390 horsepower output.
427ci, 400hp Engine (L68)
Alternate engine with improved 400 horsepower output.
427ci, 435hp Engine (L71)
Alternate engine with improved 435 horsepower output.
327ci, 350hp Engine (L79)
Alternate engine with improved 350 horsepower output.
427ci, 430hp Engine (L88)
Alternate engine with improved 430 horsepower output.
The L88 engines came equipped with closed chamber aluminum heads that operated at a 12.5:1 compression ratio.
The 1968 L88 engine came equipped with emission equipment.
An identifying characteristic of the 1968 and 1968 L88 engines, the aluminum heads were left bare and the valve covers were chromed. By comparison, the 1967 valve covers, heads and engine block were all painted Chevy Orange.
Aluminum Cylinder Heads with L71 (L89)
Aluminum Cylinder Heads for L71 Engine.
4-Speed Manual Transmission (M20)
An optional Muncie 4-speed manual transmission.
The gear ratios for the RPO M20 4-Speed Manual Transmission are: 1st Gear – 2.52:1, 2nd Gear – 1.88:1, 3rd Gear – 1.46:1, 4th Gear – 1.0:1 (Direct).
4-Speed Manual Transmission, Close Ratio (M21)
A close ratio version of the M20 Muncie 4-speed manual transmission.
The gear ratios for the RPO M21 Close Ratio 4-Speed Manual Transmission are: 1st Gear – 2.20:1, 2nd Gear – 1.64:1, 3rd Gear – 1.28:1, 4th Gear – 1.0:1 (Direct).
4-Speed Manual Trans, Close Ratio, Heavy Duty (M22)
A heavy-duty version of the Close Ratio Manual Transmission.
This heavy duty transmission came equipped with a fine spline input shaft, a larger diameter output shaft and gear teeth that utilized reduced helix angles. It was equipped with the following gear ratios: 1st Gear – 2.20:1, 2nd Gear – 1.64:1, 3rd Gear – 1.27:1, and 4th Gear – 1.00:1.
Turbo Hydra-Matic Automatic Transmission (M40)
An optional, three-speed automatic transmission.
The Turbo Hydra-Matic Automatic Transmission consisted of a 3-element hydraulic torque converter and compound planetary gear set. It was equipped with the following gear ratios: 1st Gear – 2.48:1, 2nd Gear – 1.48:1, and 3rd Gear – 1.00:1.
The M40 Turbo Hydra-Matic transmission cost $226.45 when combined with the 327 cubic inch, 300 horsepower engine, but as $237.00 when combined with the 427 cubic inch, 390 horsepower or 400 horsepower engines.
Automatic transmissions changed in 1968 from the two-speed Powerglide to the three-speed Turbo Hydra-Matic.
Off Road Exhaust System (N11)
Recessed exhaust system designed to eliminate rubbing in varying road conditions.
Telescopic Steering Column (N36)
An optional, adjustable steering column.
The Telescopic Steering Column changes the drivers distance from the steering wheel by literally telescoping the steering wheel closer to or further away from the vehicle operator.
Power Steering (N40)
Hydraulically assisted power steering.
Bright Metal Wheel Cover (P01)
Special chrome plated Corvette Rally Wheel Center Caps.
The package also included matching trim rings.
The P01 option as only made available in the 1968 model year.
Red Stripe Tires, F70 x 15, nylon (PT6)
Standard size tires with a special 3/8″ wide red sidewall stripes.
The red stripe tires were a popular option in the late sixties and early seventies. General Motors actually experimented with a number of other colors, including blue and gold sidewall stripes.
White Stripe Tires, F70 x 15, nylon (PT7)
Standard size tires with a special 3/8″ wide white sidewall stripes.
Alarm System (UA6)
A factory installed alarm system.
When activated, the alarm system would trigger the horn to sound in a repetitive pattern of short bursts.
Speed Warning Indicator (U15)
An adjustable needle on the speedometer which activates an audible alarm when speeding.
The speed warning indicator needle signals a buzzer indicating the driver is exceeding the predefined set speed. It can be adjusted by the operator of the vehicle to accommodate different speed conditions.
AM-FM Radio (U69)
A standard/stock dealer installed Corvette radio for model years 1968-1971.
The radio broadcast only a mono signal.
AM-FM Radio, Stereo (U79)
An optional dealer installed Corvette radio for model years 1968-1971.
This radio option provided a true stereo signal.
This radio featured green lettering.
The battery was moved to a compartment behind the seats to improve weight distribution and to free underhood space.
Windshield wipers were hidden under a vacuum-operated panel.
1968 Corvette Dealers Sales Brochure
Download this 1968 Corvette Dealers Sales Brochure for a quick look at the features of the car.
Recall: 1 Make: CHEVROLET Model: CORVETTE Model Year: 1968 Manufacturer: CARDONE INDUSTRIES, INC. Mfr’s Report Date: MAY 07, 2003 NHTSA CAMPAIGN ID Number: 03E032000 N/A NHTSA Action Number: N/A Component: SERVICE BRAKES, AIR:DISC:CALIPER Potential Number of Units Affected: 15899
REMANUFACTURED REAR BRAKE CALIPERS, PART NOS. 18-7019, 18-7020, 16-7019, AND 16-7020, MANUFACTURED FROM FEBRUARY 1, 2002, TO APRIL, 25, 2003., AND FOR USE ON 1965 THRU 1982 CHEVROLET CORVETTES. THE SUBJECT BRAKE CALIPERS WERE MANUFACTURED USING IMPROPERLY MANUFACTURED PISTON SEALS. THESE SEALS ARE INTENDED TO PREVENT FLUID LEAKAGE BETWEEN THE CALIPER HOUSING AND THE PISTONS. THESE BRAKE CALIPERS ARE FOR USE ONLY ON 1965 THRU 1982 CHEVROLET CORVETTE VEHICLES. THIS RECALL DOES NOT INVOLVE GENERAL MOTORS CORPORATION OR ANY OF ITS PRODUCTS.
UNDER THESE CONDITIONS, THE VEHICLE OPERATOR MAY NOT BE ABLE TO STOP THE CAR, POSSIBLY RESULTING IN A VEHICLE CRASH.
CARDONE WILL NOTIFY ITS CUSTOMERS AND ALL UNSOLD INVENTORY WILL BE REPURCHASED AND WILL PROVIDE A FULL REFUND TO CUSTOMERS. OWNER NOTIFICATION IS EXPECTED TO BEGIN DURING MAY 2003. OWNERS WHO TAKE THEIR VEHICLES TO AN AUTHORIZED DEALER ON AN AGREED UPON SERVICE DATE AND DO NOT RECEIVE THE FREE REMEDY WITHIN A REASONABLE TIME SHOULD CONTACT CARDONE AT 215-912-3000.
ALSO, CUSTOMERS CAN CONTACT THE NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION’S AUTO SAFETY HOTLINE AT 1-888-DASH-2-DOT (1-888-327-4236).
Recall: 2 Make: CHEVROLET
Model Year: 1968
Manufacturer: GENERAL MOTORS CORP.
Mfr’s Report Date: NOV 30, 1967
NHTSA CAMPAIGN ID Number: 67V117000 N/A
NHTSA Action Number: N/A
Component: SERVICE BRAKES, HYDRAULIC:FOUNDATION COMPONENTS:HOSES, LINES/PIPING, AND FITTINGS
Potential Number of Units Affected: 2781
POSSIBLE INSUFFICIENT CLEARANCE BETWEEN THE LOWER EDGE OF THE LEFT FRONT FENDER SKIRT AND THE FRONT BRAKE PIPE, JUST IN FRONT OF THE STEERING GEAR. THIS COULD ALLOW THE SKIRT TO CHAFE AGAINST THE BRAKE PIPE WHICH COULD EVENTUALLY RESULT IN WEAR THROUGH OF THE BRAKE PIPE AND LOSS OF FRONT WHEEL BRAKE SYSTEM. BECAUSE OF DUAL SYSTEM, REAR BRAKES WOULD STILL BE OPERATIVE. (REWORK THE FENDER SKIRT.)
1968 Corvette Service Bulletins
1968 Corvette Common Issues
The following list of common issues is intended for individual reference only, and may not reflect the specific issues of every 1968 Corvette. This information comes from a variety of sources including the NHTSA Defects Reports pages. While the intent of this page is to identify the common issues pertaining to the 1968 Corvette, it is not an all-inclusive list and should be used for reference only.
1968 C3 Corvette Mechanical Issues
One of the common issues with the engines in a 1968 Corvette have nothing to do with any specific mechanical issues. The issue is that, more often than not, the original engine has been replaced, and the replacement engine is not the same type/model as was installed when the car was originally manufactured.
Overheating is a common problem on early C3 Corvettes. One of the most common causes of overheating is the replacement of the stock radiator fan and fan shroud with an electric fan.
CRANKCASE VENTILATION/PCV VALVE
PCV (Positive Crankcase Ventilation) Valves are important to proper engine operation. The PCV valve allows a pressure drop (vacuum) in the engine’s crankcase. In turn, this helps the engine piston rings seal against the cylinder wall. The PCV valve also acts as a check valve under hard acceleration when engine vacuum is zero. This allows the crankcase ventilation tube that is connected to the air cleaner to draw a vacuum in the crankcase when the throttle is wide open. PCV valves are often neglected but they play an important role in engine drivability and engine life. An improperly operating/damaged PCV valve can cause hesitation, poor idling, and stalling. The crankcase should never be totally closed- it will cause extreme oil usage and oil leaks Be cautious of replacing crankcase/valve covers with aftermarket brands that do not include baffles for the PCV Valve or crankcase tubes. Also, make sure that all PCV grommets are properly sealing to ensure that the proper pressures are maintained and that oil blow-by does not occur.
One of the common issues with the transmissions in a 1968 Corvette have nothing to do with mechanical issues. The issue is that, more often than not, the original transmission has been replaced, and the replacement transmission is not the same type/model as was originally installed when the car was manufactured.
The transmission vacuum modulator that controls shift timing could have a broken diaphragm allowing transmission fluid to be drawn into the engine. A minor vacuum modulator diaphragm leak will foul the number eight plug slowly and result in a minor loss of transmission fluid. A severe vacuum modulator diaphragm leak will create smoke out the tailpipe and noticeable transmission fluid loss. The number eight cylinder intake manifold runner is where the vacuum supply to the automatic transmission modulator is located. This number eight intake manifold runner also supplies the headlamp actuator system. Therefore, this vacuum supply can create a very rough idle if both systems were leaking. Many times the fitting that screws into the intake manifold is loose.
Both the driver and passenger door windows are known to fail. There are generally two conditions which cause the window to stop operating: 1.) A blown fuse or defective relay, or, 2.) A failed power window motor. When inspecting the vehicle for a cause, always check the fuse first. The replacement of a power window motor is a time consuming process requiring access to the inner workings of the door via removal of the inner door panel.
In instances where the window fails to go up completely, inspect the window gear regulator. If any of the gear teeth are missing from the widow regulator, the gear will need to be replaced. If the teeth on the regulator gear are not damaged, the window motor will need to be removed from the regulator and inspected. A damaged worm gear (gear drive on the window motor) will require replacement of the entire window motor.
If the window rattles when the vehicle door is closed, inspect both the window regulator mounting bracket (which may be damaged/broken), and the window anti-rattle cushions. Due to age, the window cushions can become damaged or may fall off the vehicle. Fortunately they can be easily replaced at many auto parts stores.
If the window travels excessively fast during operation, inspect the power window spring. A broken spring can result in costly repairs to the to the power window motor or the window regulator gear.
1968 C3 Corvette Electrical Issues
The operation of taillights and turn signal lights may experience intermittent or total failure. Although there are a number of possible causes for this issue, the most common cause of failure is a bad ground in the taillight circuit. When troubleshooting, check for breaks in wiring and check for wiring grounds. Other possible causes for failure include bad lightbulbs, bad turn signal switch, and/or bad brakelight switch.
1968 C3 Corvette External Issues
Depending on the climate and driving conditions, the 1968 Corvette is known to develop extensive corrosion/rust in a number of areas including the frame and the “bird cage”. On the frame, the most common areas where rust is known to develop include just forward of the rear wheels, the front cross member, the framework around the doors and the windshield pillars (the area known as the aforementioned “bird cage.”) One of the tell-tale signs of a rust/corrosion issue is the presence of dampness/wetness on the forward floor areas. Severe corrosion may also resort in door sag and can adversely affect door alignment, resulting in a large (and increasing) gap between the top of the door and the fender.
HEADLAMP ACTUATOR VACUUM LEAKS
All Corvettes from 1968-1981 can have a large vacuum leak from the headlight actuator vacuum system that will affect the engine idle. When experiencing rough idle, remove the vacuum hose and plug the fitting temporarily, then check engine performance. See Transmission Modulator Vacuum Leaks above for additional information.
The rubber hoses and other components of the headlight vacuum system are known to wear out. In many instances, only one of the headlight assemblies will operate. Always check all rubber vacuum lines when even a single headlight assembly is not operating properly as many times, it the result of a failed or collapsed line.
Over time, the door hinges on all C3 Corvettes fatigue and begin to fail, causing the doors to sag and other alignment issues including broken door seals, water leaks, and road noise. To prolong the hinge life, lubricate the hinges regularly. In the event that the hinges do sag, replacing the hinge bushings and pin is also an option, although replacing the upper hinge pin will require the removal of the dashboard speedometer cluster.
The time or mileage intervals indicated on this website are intended as a guide for establishing regular maintenance and lubrication periods. Sustained heavy duty or high speed driving, or driving under adverse conditions may require more frequent servicing.
Additional Maintenance and Lubrication
In addition to the items listed above, it is also recommended that the following items are inspected every 300 miles or 2 weeks, whichever comes first:
Check Tire Pressure
Check Battery Water Level
Check Oil Level In Engine
Remove air cleaner and block throttle and choke in wide open position. Hook up starter remote control cable and insert compression gauge firmly in spark plug port. Whenever the engine is cranked remotely at the starter, with a jumper cable or other means, the distributor primary lead must be disconnected from the negative post on the coil and the ignition switch must be in the “ON” position. Failure to do this will result in a damaged grounding circuit in the ignition switch.
Crank engine through at least four compression strokes to obtain highest possible reading. Check and record compression of each cylinder. If one or more cylinders reads low or uneven, inject about a tablespoon of engine oil on top of pistons in low reading cylinders (through spark plug port.) Crank engine several times and recheck compression. If compression comes up but does not necessarily reach normal, rings are worn. If compression does not improve, valves are burnt, sticking or not sealing properly. If two adjacent cylinders indicate low compression, the cause may be a head gasket leak between the cylinders. Engine coolant and/or oil in cylinders could result from this defect.
The adjustments described apply to all carburetors used, except as noted. All adjustments are made with the engine at normal operating temperature.
Idle Speed and Mixture(1966-1970)
Remove distributor vacuum line at distributor and plug hose. Start engine and set the throttle stop screw for recommended idle speed. The choke valve must be wide open and the fast idle inoperative. Adjust one idle mixture screw at a time for smoothest, fastest idle speed. On A.I.R. cars, turn one adjusting screw at a time until engine speed drops approximately 30 rpm and starts to roll (lean mixture), then turn screw out exactly 1/4 turn for final setting. Readjust throttle stop screw for recommended idle speed. Basic setting for idle mixture screws is 2 turns open from fully closed for 1966-68, 3 turns for 1969, 1 turn for Holley 2300, Air condition to be ON, except Mark IV and all 1972.
When adjusting the idle speed be sure that the idle compensator is closed. Close it manually if necessary. After idle speed is adjusted, check by pressing down on the compensator. If speed drops, readjust idle speed. NOTE: Idle speed adjustments on cars with automatic transmissions must be made with transmission in Drive and idle stator switch, if so equipped, closed. Be sure parking brake is on.
Idle Speed and Mixture – Holley 2300
All adjustments are same as previously described except as follows: On models equipped with idle stop solenoid, adjust idle stop solenoid screw to give 1000 rpm, then adjust idle mixture adjusting screw to specified rpm. Turn idle mixture screw in (leaner mixture) until engine speed drops 20 rpm, then turn out 1/4 turn. Disconnect lead at idle stop solenoid (throttle level will rest against regular stopscrew.) Adjust this stopscrew for idle speed of 500 rpm. Do not change setting of idle stop solenoid stopscrew or idle mixture screw.
Fast Idle (1966-1976)
With the transmission in neutral, position the cam follower on the high step (2nd step, 1971-1972) of the fast idle cam. Adjust fast idle screw of Rochester carburetors to obtain recommended fast idle speed. Bend fast idle lever on Holleys. On 1970-72 models, disconnect transmission controlled spark solenoid.
With slow idle speed correctly adjusted, fully open choke and make sure fast idle cam follower is off steps of cam. With dashpot fully compressed, adjust for 1/16″ clearance between dashpot plunger and throttle lever.
Remove the air cleaner and check to see that choke valve and rod more freely. Disconnect choke rod at choke lever. Check choke adjustment by holding choke valve closed and position rod so that it contacts stop. If necessary, adjust rod length by bending rod at offset. Bend must be such that rod enters choke lever hole freely and squarely. Connect rod at choke lever and install air cleaner.
Air Injection Reactor (A.I.R.) – Description and Operation
The A.I.R. system is used to burn the unburned portion of the exhaust gases to reduce its hydrocarbon and carbon monoxide content. The system forces compressed air into the exhaust manifold where it mixes with the hot exhaust gases. The hot exhaust gases contain unburned particles that complete their combustion when the addition air is supplied.
The system consists of: An air pump, diverter valve, check valve(s), AIR pipe assemblies and connecting hoses and fittings. Carburetors and distributors for AIR engines are made to be used with the system and should not be replaced with components intended for use with engines that do not have the system.
The air pump is a two-vane pump which compresses fresh filtered air and injects it into the exhaust manifold. The pump consists of: a housing, centrifugal filter, set of vanes that rotate about the centerline of pump housing bore, the rotor, and the seals for the vanes. The centrifugal filter is replaced by first removing the drive belt and pump pulley; then pulling filter off with pliers. Care should be taken to prevent fragments from entering the air intake hole. NOTE: A new filter may squeal when first put into operation. Additionally, GREAT CARE should be taken in working on the compressor as the aluminum used is quite soft and thin. The air pump is operating satisfactorily when the air flow from it increases as engine speed increases.
The air hoses should be replaced only with hoses which are designed for AIR system use, as no other type hoses can withstand the high temperature.
Check and Adjust Dwell
Start engine then check ignition dwell. With engine running at idle, raise the adjustment screw window and insert an Allen wrench in the socket of the adjusting screw. Turn the adjusting screw as required until a dwell reading of thirty degrees is obtained. A two degree variation is allowable for wear. Close access cover fully to prevent the entry of dirt into the distributor. If a dwell meter is not available, turn adjusting screw clockwise until engine starts to misfire, then turn screw one-half turn in the opposite direction to complete adjustment.
Slowly accelerate engine to 1500 rpm and note dwell reading. Return engine to idle and note dwell reading. If dwell variation exceeds specifications, check for worn distributor shaft, worn distributor shaft bushing or loose breaker plate.
Remove distributor cap, clean cap and inspect for cracks, carbon tracks and burned or corroded terminals. Replace cap where necessary. Clean rotor and inspect for damage or deterioration. Replace rotor where necessary. Replace brittle, oil soaked or damaged spark plug wires. Install all wires to proper spark plug. Proper positioning of spark plug wires in supports is important to prevent cross-firing. Tighten all ignition system connections. Replace or repair any wires that are frayed, loose or damaged.
Disconnect the distributor spark advance hose and plug the vacuum source opening. Start engine and run at idle speed. Aim timing light at timing tab. The markings on the tabs are in two degree increments (the greatest number of markings on the “A” side of the “Q”). The “O” marking is TDC (Top Dead Center) and the BTDC settings fall on the “A” (advance) side of the “O”. Adjust the timing by loosening the distributor clamp and rotating the distributor body as required, then tighten the clamp, and recheck timing. Stop engine and remove timing light and reconnect the spark advance hose.
Inspect each plug individually for badly worn electrodes, glazed, broken or blistered porcelains and replace plugs where necessary. Clean serviceable spark plugs thoroughly, using an abrasive-type cleaner such as sand blast. File the center electrode flat. Inspect each spark plug for make and heat range. All plugs must be of the same make and number. Adjust spark plug gaps to .035 in. using a round feeler gauge. If available, test plugs with a spark plug tester. Inspect spark plug hole threads and clean before installing plugs. Install spark plugs with new gaskets and torque to specifications. Connect spark plug wiring.
Transistorized Distributor (H.E.I. System)
There are no moving parts in the ignition pulse amplifier, and the distributor shaft and bushings have permanent type lubrication, therefore no periodic maintenance is required for the magnetic pulse ignition system.
Distributor (Breaker Point System)
Check the distributor centrifugal advance mechanisms by turning the distributor rotor in a clockwise direction as far as possible, then releasing the rotor to see if the springs return it to its retarded position. If the rotor does not return readily, the distributor must be disassembled and the cause of the trouble corrected.
Check to see that the vacuum spark control operates freely by turning the movable breaker plate counter-clockwise to see if the spring returns to its retarded position. Any stiffness in the operation of the spark control will affect the ignition timing. Correct any interference or binding condition noted.
Examine distributor points and clean or replace if necessary. Contact points with an overall gray color and only slight roughness or pitting need not be replaced. Dirty points should be cleaned with a clean point file. Use only a few strokes of a clean, fine-cut contact file. The file should not be used on other metals and should not be allowed to become greasy or dirty. Never use emery cloth or sandpaper to clean contact points since particles will embed and cause arcing and rapid burning of points. Do not attempt to remove all roughness nor dress the point surfaces down smooth. Merely remove scale or dirt. Clean cam lobe with cleaning solvent, and rotate cam lubricator wick end (or one-hundred-eighty degrees as applicable). Replace points that are burned or badly pitted.
Where prematurely burned or badly pitted points are encountered, the ignition system and engine should be checked to determine the cause of trouble so that it can be eliminated. Unless the condition causing point burning or pitting is corrected, new points will provide no better service than the old points.
Check point alignment then adjust distributor contact point gap to .019″ (new points) or .016″ (used points). Breaker arm rubbing block must be on high point of lobe during adjustment. If contact points have been in service, they should be cleaned with a point file before adjusting with a feeler gauge.
Check distributor point spring tension (contact point pressure) with a spring gauge hooked to breaker lever at the contact and pull exerted at 90 degrees to the breaker lever. The points should be closed (cam follower between lobes) and the reading taken just as the points separate. Spring tension should be 19-23 ounces. If not within limits, replace. Excessive point pressure will cause excessive wear on the points, cam and rubber block. Weak point pressure permits bouncing or chattering, resulting in arcing and burning of the points and an ignition miss at high speed.
Install rotor and distributor cap. Press all wires firmly into cap towers.
Battery and Battery Cables
The top of the battery should be clean and the battery hold-down properly tightened. Particular care should be taken to see that the top of the battery is kept clean of acid film and dirt. When cleaning batteries, wash first with a dilute ammonia based or soda solution to neutralize any acid present and then flush off with clean water. Keep vent plugs tight so that the neutralizing solution does not enter the cell. The hold-down bolts should be kept tight enough to prevent the batter from shaking around in its holder, but they should onto be tightened to the point where the battery case will be placed under a severe strain.
To ensure good contact, the battery cables should be tight on the battery posts. Oil battery terminal felt washer. If the battery posts or cable terminals are corroded, the cables should be cleaned separately with a soda solution and wire brush. After cleaning and before installing clamps, apply a thin coating of a petrolatum to the posts and cable clamps to help slow corrosion.
If the battery has remain undercharged, check for loose or defective fan belt, defective alternator, high resistance in the charging circuit, oxidized regulator contact points, or a low voltage setting. If the battery has been using too much water, the voltage output is too high.
Inspect for deteriorated or plugged hoses. Inspect all hose connections. On engines with closed element air cleaners, inspect crankcase ventilation filter and replace if necessary. On engines with open element air cleaners, remove flame arrestor and wash in solvent then dry with compressed air.
Check the brake fluid regularly, for as the brake pads wear the level will drop rapidly. It should be replenished only with the recommended fluid. Check disc brake assemblies to see if they are wet; it would indicate a leaking cylinder.
Disc brakes do not need periodic adjustments; they are self adjusting. The pads should be replaced when the friction material gets down to 1/16″. This is when the groove in the center of the pad is gone. Check by removing wheel and looking directly into caliper.
Clutch Pedal Play
Check clutch action by holding pedal 1/2″ from floor and move shift lever between first and reverse several times, with engine running. If shift is not smooth adjust clutch. Free play with pedal released is approx. 1-1/4″ to 2″ and 2″ to 2-1/2″ for heavy duty.
At clutch lever near firewall remove clutch return spring. To decrease clutch pedal free play remove clutch pedal return spring and loosen lower nut on clutch pedal rod; take up play with upper nut. Continue until proper play is obtained, then securely tighten top nut and replace spring. To increase pedal play work nuts in opposite sequence.
Disconnect control linkage at carburetor throttle lever. Hold carburetor throttle lever in wide position. Pull control linkage to wide open position. (On vehicles equipped with automatic transmission, pull through detent.) Adjust control linkage to freely enter hole in carburetor throttle lever. Connect control linkage at throttle lever.
Throttle Linkage Adjustment (Powerglide)
Remove air cleaner, disconnect accelerator linkage at carburetor. Disconnect accelerator return and trans. road return springs. Pull upper rod forward until transmission is through detent. Open carburetor wide open, at which point ball stud must contact end of slot in upper rod. Adjust swivel on end of rod if necessary.
Pull detent switch driver to rear until hole in switch body lines up with hole in driver. Insert a 3/16″ pin through hole to depth of 1/8″, and loosen mounting bolts. Open throttle fully and move switch forward until lever touches accelerator lever. Tighten mounting bolt and remove pin.
EGR Valve Check
A rough idling engine may be caused by a malfunction of the valve. Check by pinching vacuum hose to carburetor with engine idling. If idling smooths out, the valve should be removed for cleaning or replacement if something appears to be broken.
Lubrication Engine Oil
The car should be standing on level ground and the oil level checked with the dipstick. Withdraw the dipstick, wipe it with a clean rag, replace and withdraw again. The mark made by the oil on the lower end of the dipstick will indicate the oil level. If necessary, oil should be added through the filler cap. Never let the oil level fall so low that it does not show at all on the dipstick. If in doubt, it is better to have a bit too much oil than too little. Never mix oils of different brands, the additives may not be compatible.
Engine Oil Drain and Replacement
Place a pan under the oil pan drain plug and remove plug. Be sure pan is of a large enough capacity to hold the oil. Move pan under filter and remove filter by turning if counterclockwise. Clean gasket surface of cylinder block. Coat gasket of new filter with engine oil. Thread filter into adapter. Tighten securely by hand. Do not overtighten filter. Remove drop pan.
Remove drain pan. Inspect oil pan drain plug gasket and replace if broken, cracked, or distorted. Install drain plug and tighten. Fill crankcase to required level with recommended oil. Operate engine at fast idle and check for oil leakage.
When changing oil filter, add one additional quart.
Check fluid level with engine idling, transmission in neutral and engine at normal operating temperature. Add fluid as needed to bring level to mark. Do not overfill.
Every 12,000 miles or sooner, depending on service, remove fluid from sump and add new fluid. Operate transmission and check fluid level. Every 24,000 miles the transmission sump strainer of the Turbo Hydra-Matic transmission should be replaced.
Raise car on lift, clean dirt and grease from area around the filler plug. Plug is located on side of transmission case. Remove plug and place finger tip inside hole. The oil should be just about level with the bottom edge of the hole. Add oil as needed, using a plastic syringe.
Change cam lubricator end for end at 12,000 mile intervals. Replace at 24,000 mile intervals.
With the car standing level, clean dirt and grease from area around filler plug. Remove plug and place finger tip inside hole. The oil should be just about level with the bottom edge of the hole. Add oil, with a plastic syringe, as needed.