Chevrolet Corvette C3 - Buyer's Guide

By: Unique Cars magazine

Date: 10.01.2021

There's a huge amount of style and attitude for the dollar on offer here, but the presence or absence of chrome bumpers can affect values significantly

Meddling with an icon is serious business and Chevrolet when designing its third generation Corvette had no idea that social and legislative change would so dramatically affect this model during 15 turbulent years of existence.

The C3 shape, in common with many GM designs, was based on a show car; this one called the Mako Shark 2. Mechanically it drew extensively with the C2 Sting Ray it replaced, but was engineered to accommodate GM’s biggest and most potent V8 engines.

Early C3s are distinguished by their slim, chrome-plated bumpers and full convertible Roadster bodies that supplemented the fixed-roof coupe. After 1972, when engine output also suffered a dramatic downturn and impact-absorbing ‘5mph’ plastic bumpers replaced the chrome bars, Corvettes in Roadster form were doomed to disappear as well.

C3 Corvette coupes had since 1968 been available with lift-out roof panels. Once threats from legislators to ban full convertibles became serious (although laws were never enacted) ‘T Roof’ cars became the only way to own an open-top C3.

Due to a combination of factors, power output and performance dwindled as well during the 1970s. Advertised output during 1968 from a 350 cubic inch engine with 11:1 compression was 350bhp (260kW) but by 1975, with emission controls, lower octane fuels and lower compression all taking a bite and ‘truthful’ power figures a legal requirement, it had crumbed to just 123kW.

Still, the Corvette remained America’s best loved sports car and sales continued to climb. While total numbers during a depressed 1972 barely made 27,000 cars, 1979 saw sales come within a whisker of 50,000.

Corvettes had been arriving in Australia since the 1950s, but the 1970s saw floodgates open and hundreds of new C3s arrive. Laws at the time required virtually all of them to be RHD converted, sometimes with dire results.

By the 1990s, conversion was no longer mandatory and ‘historic’ registration schemes allowed LHD cars to be routinely used on public roads. These changes reduced the cost of new arrivals and irritated longer-term owners who were still trying to recover their conversion costs.

The C3 range provides plenty of choice to suit a range of budgets. Cars from different points along the C3 timeline incorporate differing features - such as a lift-back rear window on later versions - to attract buyers with diverse needs.

Owning an entry-level C3 should cost less than $30,000. That money will currently buy a late 1970s, plastic bumper 5.7-litre automatic with OK paint and plenty of life in it mechanically.

Jump to $50,000 and chrome bumper 1968-72 Roadsters becomes viable. Or perhaps spend a little less on a 1978 Pace Car replica, 1978 Silver Anniversary edition or 1982 Collector Edition.

An outlay exceeding $100,000 will rarely be needed, even when your car of choice is a big-block, four-speed manual Roadster.

Corvettes with engines of seven litres and larger were built from 1968-74, although most in our market will be 454 cubic inch units from the 1970s that were rated at 270bhp (200kW). Although larger in capacity, the 454 lacked the high-end urge of a 427.

VALUE RANGE CHEVROLET CORVETTE (1968-73, 350 Roadster)

Fair: $20,000
Good: $40,000
Excellent: $55,000

(Note: exceptional cars will demand more)

BUYER'S CHECKLIST:

Body & chassis

Plastic bonded to a steel frame is durable and strong, up to the point where the metal rusts and the plastics crack. Then lots of money is needed to salvage the car. Have a specialist check any Corvette you’re considering, especially one that has spent most of its life overseas. The front air-dam and sills are vulnerable to kerb and speed-bump damage but this kind of peripheral injury is easily fixed. Rear spring hangers need to be inspected on a hoist for rust. When inside the car check door and roof seals for damage that may permit wind and water entry. Make sure that the lights emerge quickly and in unison.

If the motors fail. each light has a manual over-ride.

Engine & transmission

Most C3 ‘Vettes used Chevrolet’s astoundingly reliable LT1, 350 cubic inch engine. These are a basic overhead-valve design with one carburettor and no invasive electronics. The valves can be noisy when cold, but shouldn’t rattle alarmingly at other times. Engine bay space is tight and cooling can be marginal so check this during your test drive. Affected cars will need the radiator cleaned or replaced and perhaps a new water pump. Cars with 427 or 454 cubic inch blocks need to be verified as originally supplied with these engines. The Muncie manual gearbox is reliable, as is the T350 automatic. A shuddering or slipping clutch will prompt a price cut due to the amount of work required to replace it, even though the clutch unit itself is cheap.

Suspension & brakes

The Corvette design blends contemporary suspension components with an ancient transverse leaf spring at the rear yet delivers surprisingly effective handling. Lack of steering feel lets these cars down though and this is accentuated by RHD conversion. Cars converted within the past 20 or so years should have engineering certification but earlier swaps need to be checked for safety by a specialist. Edge-worn tyres indicate alignment problems and steering that won’t self-centre is another hint of problems. Check brake rotors for heat spotting and scoring. New ones, depending on quality, cost from $300-1000 per pair.

Interior & electrics

The most recent of these cars will be 38 years old and trim, if not already been replaced, will be due. Leather discolours and splits, especially if it’s had to contend with eavyweight occupants plus sun exposure. Electrics in fibreglass cars can suffer earthing issues so check that everything works. Be sure to run the air-conditioning where fitted for several minutes to make sure it does produce genuinely cold air. Check around the battery box (remove the battery if possible) for damage caused by leaking acid.

1967-1982 CHEVROLET CORVETTE C3

Number made: 133,450 (approx) 1968-72 396,150 (approx) 1973-82
Body styles: GRP/steel integrated body/chassis two-door coupe & roadster
Engine: 5665cc, 6996cc or 7410cc V8 with overhead valves & single downdraft carburettor
Power & torque: 200 kW @ 4800rpm, 486 Nm @ 3200rpm (LT1 350 V8)
Performance: 0-96km/h 7.4 seconds, 0-400 metres 15.6 seconds (350 manual)
Transmission: Four-speed manual, three-speed automatic
Suspension: Independent with coil springs, upper & lower control arms, telescopic shock absorbers and anti-roll bar (f)
Independent with semi-elliptic spring, locating links, anti-roll bar and telescopic shock absorbers (r)
Brakes: Disc (f) disc (r) power assisted
Tyres: F70x15 cross-ply

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