Both cars were a result of the same General Motors project and share the same floorpan and engine constructions, but with one main difference being the use of metric measurements for the Opel and imperial ones for the Vauxhall.

The HA Viva was powered by a 1,057 cc (64.5 cu in), overhead valve, four cylinder, front-mounted engine driving the rear wheels.

It was comparable in size and mechanical specifications with the new Opel Kadett released a year earlier in continental Europe, being a result of the same project — with the two cars sharing much of their inner structure and similar overall dimensions.

The assembly featured a double wishbone/vertical telescopic dampers suspension design in combination with a transverse leaf spring attached to the front crossmember at its centre position and the entire unit could be removed and adapted to another vehicle.

[7] The HA, however, suffered severely from corrosion problems[citation needed] along with other Vauxhall models of the time and very few of this model remain – one of the main problem areas being the cappings along the top side edges of the luggage compartment badly corroding and allowing water to enter, consequently leading to severe structural corrosion in the luggage-compartment floor area.

[8] It differed from the saloon in being taller, and thousands were bought by the GPO (later British Telecom), their bright yellow HA vans becoming a common sight.

The HB Viva, announced in September 1966[10] and sold by Vauxhall until 1970, was a larger car than the HA, featuring coke bottle styling, and was modelled after American General Motors (GM) models such as the Chevrolet Impala/Caprice of the period, and was a solely Vauxhall design — likewise Opel had also developed the equivalent Opel Kadett B with no platform sharing, unlike the previous generation.

It featured the same basic engine as the HA, but enlarged to 1,159 cc, but with the added weight of the larger body the final drive gearing was reduced from 3.9 to 1 to 4.1 to keep the nippy performance (except the SL90 which retained the 3.9 diff having the power to cope with the higher ratio).

Lateral location and anti-squat of the rear axle was achieved using upper trailing arms mounted at approximately 45° fixed to lugs at the top of the differential.

The HB set new standards for handling in its class as a result of the adoption of this suspension design, where many of its contemporaries stuck with leaf springs and MacPherson struts.

Front disc brakes came with the 90 and overhead cam engine models, while a larger 12 gallon fuel tank was also part of the 1600 and GT package.

[11] Second on the list, with 24% of cars triggering brake fault reports, was the similarly configured Opel Kadett estate.

[11] Although it avoided the bottom spot in other individual categories, the poor score achieved by the brakes left the Viva with the highest overall rate of failure of the 34 passenger cars included in sufficient numbers to feature in the reports of the Swedish test results.

The introduction of the four-door option coincided with various minor improvements to the interior trim, while 'auxiliary' switches were relocated from a remote panel to positions nearer to the steering wheel.

[12] The GM "energy absorbing" steering column was now fitted to all models and the fuel tank capacity was increased from 8 to 12 British gallons (36 to 55 litres).

[13] By the time of the readership poll, the HB Viva was within a year of being replaced even though the 1600 version itself had only been offered since 1968, so the sample will have been relatively small: it appears that the low satisfaction rate may have reflected not so much the car's design but rather a lack of effective quality control in the manufacturing processes.

The HB had better underbody protection, but UK cars were still prone to rusting through the front wings in the area behind the headlights where water, mud and salt could accumulate.

[citation needed] The HC Viva (1970–79) was mechanically the same as the HB but had more modern styling and greater interior space due to redesigned seating and positioning of bulkheads.

[18] The American influence was still obvious on the design, with narrow horizontal rear lamp clusters, flat dashboard with a "letterbox" style speedometer, and a pronounced mid bonnet hump that was echoed in the front bumper.

It was available in deluxe and SL forms, with the latter sporting four headlights and finally resurrecting the missing 2.0 twin-carburettor engine from the HB Viva GT.

The whole range of Viva-based cars received safety equipment upgrades at the same time, with power-assisted dual-circuit brakes (with discs in front) being made standard.

[citation needed] For 1977, the SL was replaced by the GLS, essentially marrying the plusher Magnum trim and equipment with the base 1,256 cc pushrod ohv engine.

Production ceased at a time when European manufacturers were making the transition from rear-wheel-drive saloons to front-wheel-drive hatchbacks in the family car market.

The end of production of the HC Viva in 1979 marked a significant moment for Vauxhall, as it would ultimately prove to be the last car to be completely designed by the company with no input from Opel.

The millionth Viva, a gold HC, was driven off the production line by politician John Eden amid much celebration on 20 July 1971.

After a 1975 facelift and some changes to the lineup, these lost the "Firenza" badges and were sold simply as the Chevrolet 1300 and 1900, as the smaller 1960 cc version had replaced the earlier 2.5.

The Firenza range originally consisted only of four-door saloons, but South Africa also saw a three-door hatch developed off this rather than taking on the then new Chevette/Kadett City; this was first shown in June 1976 and the first car rolled off the production line in August.

With the new Chevrolet Chevair recently introduced, cost prohibitions made such a creation a better proposition than bringing in an all-new car.

At the time of introduction, the Weber carburetted manual 1900 claimed 80 kW (109 PS; 107 hp) SAE and a top speed of 149 km/h (93 mph) for the Hatch.

[29] The Firenza was plagued with significant quality problems which were made worse with the lack of availability of spare parts due to the frequent labour strikes in the UK at the time.