Chevrolet Turbo-Thrift engine

There were other major differences between the Turbo-Thrift engine and the Stovebolt:

• Bore spacing matches the Chevrolet small-block V8's 4.4 inches,
• Stroke of the 194 and 230 engines is the same 3+1⁄4 in (82.6 mm) as the 327 small-block and 348 big-block V8s
• Wedge-type "closed chamber" cylinder heads with a "squish" area surrounding the combustion chamber cavity,
• Stamped ball-pivot stud-mounted rocker arms were introduced, similar to the V8, with a 1.75:1 ratio, rather than the earlier shaft-mounted 1.477:1 rockers.

The first use of the new engine series was the 194 cu in (3.2 L) Hi-Thrift version in the 1962 Chevy II; the following year, Chevrolet passenger cars adopted the 230 cu in (3.8 L) version across the range. Studebaker and Checker also began using the engine in 1965.^[3]: 341 Chevrolet and GMC trucks, which previously used the Stovebolt and GMC V6 engines, also switched to using the Turbo-Thrift from 1963 through 1988, as did Pontiac in 1964 and 1965. A 153-cubic-inch (2.5 L) inline-4 version of this engine was also offered in the Chevy II/Nova line through the 1970 model year.

After several years of steadily declining sales (just 3,900 units in the 1972 model year),^[3]: 881 the straight-six was dropped from Chevrolet's full-sized cars for 1973, the first time the full-sized Chevrolet had not been available with a six-cylinder since 1928. However, when the B-body line was downsized in 1977, the engine was reintroduced.^[3]: 881 The base six cost about US$334 less than a V8, and weighed some 188 lb (85 kg) less.^[3]: 881

Overseas, the engine was also mass-produced in Brazil. It was used in the Chevrolet Opala from 1969 (230) to 1992 (250). It was also used in light trucks, including the Chevrolet Veraneio. The Brazilian version of the GMT400 – the Brazilian Chevrolet Silverado – is powered with a 4.1 instead of the Vortec 4300 V6. Brazilian-produced sixes manufactured to the 2001 model year gained multipoint fuel injection, unlike the US-manufactured sixes, which retained the Rochester Monojet one-barrel carburetor. These inline-sixes and their four-cylinder siblings were converted for marine usage by Mercruiser and Volvo Penta, and also used in stationary applications (such as power generation) and in Clark forklifts.^[4] Aftermarket port fuel injection and re-engineered cylinder heads have been the norm, although parts for the inline-six, such as aftermarket intake manifolds (from a three-carburetor setup or a single 4-barrel carburetor), exhaust headers, and hybrid cylinder heads based on Chevrolet's small-block engine are costlier than those for the small-block, unlike the rival AMC inline-six (which has a cult following with Jeep enthusiasts, especially with the 4.0 L). Chevrolet's inline-six engine was also manufactured in Argentina and South Africa.

The Hi-Thrift 194 was introduced as the optional engine in the 1962 Chevy II. Bore and stroke are 3+9⁄16 in × 3+1⁄4 in (90 mm × 83 mm), for a total displacement of 194 cu in (3,185 cc).^[5] It was also optional in the 1964 G10 Chevy Van 1⁄2-ton vans, and standard in the G10 in 1965 and 1966; it was not available in the C/K10 1⁄2-ton trucks.^[6] The engine produced peak power of 120 hp (89 kW) (gross) and 177 lb⋅ft (240 N⋅m) of torque.^[7]

The 194 variant ended production in North America after 1967, but remained in use by General Motors' Argentinian subsidiary until the mid-1970s. GM de Argentina also developed a 109.7 cu in (1,797 cc) four-cylinder version called the "Chevrolet 110" for their Opel K 180 compact car.^[8]

Pontiac's 215 cu in (3.5 L) (1964–1965) was a smaller bore of 3.75 in (95.25 mm) version of the 230 cu in (3.8 L) Chevrolet straight-six engine. One oddity is the crankshaft bolt pattern; in lieu of the Chevrolet V8 bolt pattern (also shared with the rest of the third-generation six), the Pontiac V8 bolt pattern is used.

The Turbo-Thrift 230 (also known as the High Torque 230 in Chevrolet trucks), with 230 cu in (3,768 cc) displacement, replaced the long-stroke 235 cu in (3.9 L) version of the Stovebolt six beginning in 1963. Bore and stroke were 3+7⁄8 in × 3+1⁄4 in (98 mm × 83 mm). It was also used by Chevrolet and GMC trucks, primarily for the half-tons. It produced a peak 140 hp (104 kW) at 4,400 rpm and 220 lb⋅ft (298 N⋅m) at 1,600 rpm. North American production of this variant ceased in 1970. It was also built in Latin America and was in production in South Africa until at least 1982, where it powered a multitude of different cars. A four-cylinder version of this engine was also built, the Super-Thrift 153.

The Turbo-Thrift 250 (also known as the High Torque 250 in trucks) version was introduced in 1966, with the same 3.875 in (98.4 mm) bore as the 230 and a longer 3.53 in (90 mm) stroke for a larger 249.8 cu in (4.1 L; 4,093 cc) displacement. Between 1975 and 1984, an integrated cylinder head was produced (intake manifold and cylinder head were a single casting with a bolt on exhaust manifold). One-barrel intakes were used in passenger cars and trucks through 1978. Starting in 1979, a two-barrel intake fitted with a Rochester Varajet carburetor and dual take down exhaust manifold were used in trucks and vans. The "integrated" cylinder head and intake manifold claimed to have resulted in increased low end torque and fuel economy inclusive of a smoother operation, lowering NVH (noise, vibration, and harshness).

The engine was sold in various states of tune and under several different RPO codes over its production life. The L22 was the passenger car version, sold until 1979. The LD4 was the truck version, sold until 1978. The LE3 replaced the LD4 in 1979 and was produced until 1984.

In the late 1970s, the Chevrolet 200, Chevrolet 229 and Buick 231 V6 engines gradually replaced the 250 straight six in passenger cars in North America, with use of the engine discontinued after the 1979 model year. The 250 engine continued to be used in GM trucks until 1984, after which it was replaced by the 4.3 L V6 (essentially a 350-cubic-inch (5.7 L) Chevy small-block V8 with the two rear cylinders removed). It was also used in a number of large sedans by Chevrolet of South Africa until 1982.

Production continued in Brazil (known as the 4.1 there) until 1998 in passenger cars, when the Chevrolet Omega A was replaced by rebadged Australian Holdens. It was used until 2001 in the Brazilian Chevrolet Silverado, after which the engine line was discontinued. Latter-day Brazilian-produced engines featured electronic multipoint fuel injection, distributorless ignition system and redesigned cylinder heads with smaller intake ports.

GM did not produce another straight-six engine in North America until the introduction of the GM Atlas engine in late 2001.

When long distance racing restarted in Brazil in 1973, the Chevrolet Opala and the Ford Maverick were the main contenders. The Maverick's engine was almost one liter larger than the Opala's, however. Drivers Bob Sharp and Jan Balder, who shared a ride to second place in the "24 Hours of Interlagos" in August of that year in an Opala, pressured General Motors do Brasil to field a more powerful racing engine.

By coincidence, engine development manager Roberto B. Beccardi had already been working on such a performance engine project out of his own initiative, but had lacked factory support or approval. 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 launched two years later: the project engine was similar to the four-cylinder units, did not get a vibration damper, and used the cooling fan 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, called "Quadrijet" in Brazil (no relationship to GM's own Rochester Quadrajet), with performance roughly equivalent to the 250.^{[citation needed]}

The 250-S has 171 hp (126 kW) and 229.7 lb⋅ft (311 N⋅m) at 2,400 rpm.

Opala SS

Chevrolet Opala SS 250-S in drag race

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The High Torque 292 engine, displacing 292 cubic inches (4.8 L), was used in Chevrolet and GMC trucks beginning in 1963 and Step-Van/Value-Vans beginning in 1964. It was also the standard engine in the Chevy Van/GMC Vandura G20 and G30 from 1975 to 1978. It is differentiated from the 194/230/250 engines by a 1+3⁄4 inches (44.5 mm) taller block deck and relocated passenger-side engine mount. Although it had had a larger displacement than its 261-cubic-inch (4.3 L) Stovebolt predecessor it was approximately 2 inches (51 mm) shorter and 1⁄4 inch (6.4 mm) lower.^[54] Flywheel bolt pattern is the same as the six and V8, with 1⁄2 inch (12.7 mm) bolts for the flywheel if produced after the 1966 model year.

Production of the engine was shifted to Mexico in 1980, and later variants of this engine were marketed as the High Torque 4.8 L and by its RPO code L25 It retained the separate intake (with a Rochester Monojet carburetor) and exhaust manifolds as used with the short deck motors (194–250).

Availability of the 4.8 L engine was slowly curtailed from the late 1970s until production ceased entirely in 1989, and it was replaced by the 4.3 L V6. By 1987, it was only available (outside of California) as an option in 3⁄4-ton and 1-ton R/V-series trucks, and as the base engine in P20 and P30 Step-Vans.