Chevrolet Opala - Engines

Engines

Under the hood, which opened backwards, the Opala offered three engine choices: the straight-4 153 in³ (2503 cc), the Pontiac Iron Duke-4 151 in³ (2497 cc) and the straight-6 230 in³ (3764 cc). 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 carburetors.

The Opala engines had been already used for years in the U.S.: the 153 in³ had emerged in the 1962 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 carburetors, 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 112.5 mph (181.1 km/h) and acceleration time from 0 to 60 mph (97 km/h) in about 11 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 rough, 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.

Engines:

• 151 in³ 4-cylinder (2.5 L) - 98 hp (73 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) - 80 hp (60 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)