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The Chevrolet Opala was a mid-size car sold by General Motors Corporation from 1969 to 1992. It was derived from the German Opel Rekord and Commodore, but used GM USA sourced engines, two four-cylinder engines: the 151-4 Iron Duke from Pontiac, the Chevrolet 153-4 from Chevy II/Nova and the six-cylinder 250 from the current line of North American car/light truck production. GM manufactured about one million units including the Opala sedan, Opala Coupé and the station wagon variation, the Opala Caravan. It was replaced by the Chevrolet Omega in 1992, also an Opel spinoff. Before this car, Chevrolet only built light trucks and pick-up trucks, so, the Opala was its first passenger car made in Brazil.
It was used by the São Paulo Police for many years. The military dictatorship used the Opala for its agents through the 1970s. Its reliability and easy maintenance made the Opala the choice of many taxi drivers and also popular on racetracks.
Its 250 in³ engine (4.1 L) was used in its replacement, the Chevrolet Omega, but making use of Electronic Fuel Injection, in GLS and CD trims from 1995 to 1998. Some of the components and chassis were used for an exotic car called Santa Matilde.
Installed in Brazil since January 1925, General Motors restricted itself to assemble, and then, manufacturing pick-ups, utilities and trucks until the mid-1960s. Only then was decided to produce its first national Chevrolet.
The options oscillated between the large American cars from the traditional car line, like the Impala, and the lighter and economical models from German subsidiary Opel - Kadett, Olympia, Rekord and Commodore - that came to Brazil imported in small quantities. After hesitating between the small Kadett and the large Rekord/Commodore line, GMB opted for the second one, but later introduced the Kadett too.
On November 23, 1966, in a Press Conference at the Club Atletico Paulistano, in São Paulo, GM announced the start of Project 676, the future Chevrolet Opala.
The name Opala, comes from a precious stone, colourless when extracted from the soil, but that acquires multiple tones when exposed to light. It was also commented that it, the merger between Opel and Impala, as it was derived from the German Opel Rekord, but one of its engines (the 230 in³, and later, 250 in³ Straight-six) came from North American Chevrolet Impala. Even GM admits that was not set to, when that name - one of six finalists from thousands of suggestions - was disclosed by a journalist. Its rapid acceptance with the general public led to the approval of choice.
At the opening of the 6th São Paulo Auto Show, on November 23, 1968, Opala appeared on a rotating stage in a 16,140 square feet (1,499 m2) stand. Around the novelty, spectacles including counting with the presence of Stirling Moss and several models were enscenated every half hour.
The first model was the four-door sedan, in the trims "Especial" (Standard) and "Luxo" (Luxe). Its attractive lines used the solution of curvy lines from the windscreen to rear fender, a shape that was referred to as "Coke Bottle style", already in use at the time, as it was first shown on 1967 Chevrolet Camaro, 1967 Pontiac Firebird and 1968 Chevrolet Corvette, but some hints of the upcoming style were already clear on the 1965 Chevrolet Impala fastback coupé. The round headlamps (not squared, as in the Opel Rekord and Commodore), distinguished an egg crate grille, distinctively Chevrolet style, that separated the Opala from its European Opel syblings and the park/turning lamps, were fitted below, in the front bumper. In the back, a chrome strip with the "Chevrolet" name in black linked in the more expensive trim, the small rectangular tailights, in the extremities of the rear overhang, with the small reverse lights in the rear-bumper. Just above this was the fuel tank cap. The "Opala" badge, was fitted in the rear fenders, and the engine badges - 2500 or 3800 - next to the front doors. The chrome wheelcovers fitted just fine with the whitewall tires.
Both versions came standard with front bench seats (bucket seats weren't available at the beginning of production, but were later adopted) and steering-column shifter. The two models differed in trim levels: reverse lights, fuel tank lock and rear valance chrome strip were available only on "Luxo" model.
Under the hood, that opened backwards, the Opala offered three engine choices: the straight-4 153 in³ (2.503cm³), the Pontiac Iron Duke-4 151 in³ (2497 cm³) and the straight-6 230 in³ (3.764 cm³). The trio was of very traditional design, with cast iron cylinder block and head, overhead valves, pushrods and steel pressed rocker arms, whose spherical fulcrum was a proprietary GM's creation -Fuel feed from either one or two barrel carburators.
The Opala engines had been already used for years in the U.S.: the 153 in³ had emerged in the 1961 Chevrolet Nova, becoming the first inline four in Chevy since 1928, and the 230 in³ appeared in the 1963 Impala. The 151 in³ Pontiac Iron Duke was also found on AMC Jeeps and Eagle, and was known for versatility and toughness. Known for its reliability the 153 in³, was used as the corporation standard until the 1980s. The Straight-six later served as a stationary engine, school bus engine and even forklifts.
The larger engine crankshaft bearings had seven supports (five in four cylinders) and the generous, if not even redundant, size of its inner moving parts helped with its durability and exceptional smoothness. The hydraulic valve lifters contributed to that later feature, easying maintenance.
The straight six biggest limitation through the years was poor distribution of air-fuel ratio to the cylinders. Number one and six received the poorest, with higher percentage of air in the mixture, while the central ones tended to get richer mixture, unbalancing the stoichiometric engine efficiency. That bad feature was easily solved by installing a race intake manifold that sported two or three two-barrel carburators, as in Stock Car racing. Only in 1994, with the Omega and the multipoint injection, the problem was finally solved.
The performance of Opala 3.8L was actually very pleasing: with a top speed of 102.5 mph (165.0 km/h) and acceleration time from 0 to 60 mph (97 km/h) in about 13 seconds, was the fastest Brazilian car of its time, while it was losing the post after a year to the Dodge Dart whose 318 in³ V8 had all a straight six needed. The two 2.5L did not offer so much brio, but were torquey enough for everyday use. The main complain over the four cylinder engines was about their roughness - so much rogh, that at the time, GM employees called the Four "little Toyota", in allusion to the diesel engine installed other locally made Toyota Bandeirante (local name for the Land Cruiser).
The two versions, Especial and Luxo, had 3-speed manual Gearbox, Rear wheel drive, front independent suspension and rear live axle, both with helical springs. In front, the suspension elements were anchored to one side, set in Unibody by screws, which only later would be known as Subframe. The tires were the first Tubeless to be used in a model manufactured in Brazil, and used Clutch spring type "Chinese hat", or diaphragmatic spring, which began to popularize in the world.
- Iron Duke GM L4 151 2.5L motors
- 151 in³ 4 cylinder (2.5 L) - 94 hp (70 kW) Gross - (1974-1976)
- 151 in³ 4 cylinder (2.5 L) Ethanol - 98 hp (73 kW) Gross - (1980-1992)
- 151-S in³ 4 cylinder (2.5 L) - 98 hp (73 kW) Gross - (1974-1992)
- 153 in³ 4 cylinder (2.5 L) - 80 hp (60 kW) Gross - (1968-1973)
- 230 in³ 6 cylinder (3.8 L) - 125 hp (93 kW) Gross - (1968-1971)
- 250 in³ 6 cylinder (4.1 L) - 140 hp (100 kW) Gross - (1971-1975)
- 250 in³ 6 cylinder (4.1 L) - 148 hp (110 kW) Gross - (1975-1988)
- 250 in³ 6 cylinder Ethanol (4.1 L) - 155 hp (116 kW) Gross - (1984-1990)
- 250-S in³ 6 cylinder (4.1 L) - 171 hp (128 kW) Gross - (1976-1988)
- 250/S in³ 6 cylinder (4.1 L) 118 hp Net (1988-1990)
- 250/S in³ 6 cylinder (4.1 L) 121 hp Net (1990-1992)
- 250/S in³ 6 cylinder Ethanol (4.1 L) 141 hp Net (1990-1992)
The 250-S Engine
When the long duration races restarted in Brazil, in 1973, the Opala found a great competitor, the Ford Maverick, which was powered by an engine whose displacement was almost one liter bigger. It took Bob Sharp and Jan Balder, that gained a second place in the "24 Hours of Interlagos", in August of that year in an Opala, to pressure GMB to field on race tracks a more powerful engine.
By coincidence, engine development manager, Roberto B. Beccardi, was working on this engine hopping up project out of his own initiative, but he did lack impulse from factory and was not obtaining any approval. This impulse came right from these two pilots.
Thus, in July 1974 GM started to offer the 250-S engine as an option for the Opala 4100. It was slightly different from the version that would be launched two years later: the project of the motor was similar to that of the four cylinders units, did not get a vibration damper and the cooling fan came from the standard 2500, with four blades instead of six.
The Opala was now much faster than the Maverick GT and Ford did not waste time. It quickly homologated a version with four barrel carburetor, simply called "Quadrijet" in Brazilian parlance, and have no relationship with GM own Rochester Quadrajet carburator, found on GM Corp. various V 8 engines. In the racetracks, the accounting determinative factor for winning was pilots skill and pit organization on the track. The rivals walked side-by-side.
- 3-speed Manual (steering column shifter)
- 4-speed Manual (floor mounted shifter)
- 5-speed Manual (floor mounted shifter)
- 3-speed Automatic (steering column or floor mounted shifter)
- 4-speed Automatic (floor mounted shifter)