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General Chevy Straight 6 Data - 3rd Generation

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3rd Generation

Chevrolet's third-generation inline-6 was introduced in 1962 and produced through 1988. Although the exterior dimensions were similar to the previous Stovebolts, this generation was lighter and had a different cast-in bell housing pattern. Manual transmission bellhousings, automatics, and starter motors became interchangeable with both small block and large block Chevrolet V8s.

There were other major differences. The Gen-3 crankshafts had 7 main bearings (increased from 4). The 230 reduced stroke to 3.25" from the comparable 235 design's 3.9375". The combustion chamber changed to a conventional wedge design much like the V8. The harmonic damper gained cast-in pulley provisions. Air-conditioned vehicles had a stamped-steel pulley bolted up front. Stamped and stud-mounted rocker arms were introduced, similar to the V8, and the ratio was close to the one used in the Chevrolet GEN IV big block (1.75:1 ratio) rather than the shaft-mounted earlier rockers at 1.477:1.

The first usage was in the newly-introduced 1962 Chevy II; the following year, Chevrolet passenger cars (alongside Checker Marathons since 1965) used this powerplant until 1977 (1979 for Camaros, Novas, and Full Size Chevys). Chevrolet/GMC trucks, which previously used the Stovebolts (235 and 261), also used some members of this family from 1963 through 1984, as did Pontiac in 1964 and 1965. There was also a inline-4 version of this engine. After slow sales (just 3,900 units in the 1972 model year), the straight six was dropped from Chevrolet's full-sized cars for 1973, for the first time since 1928; it would be restored in 1977. The base six cost about US$334 less than a V8, and weighed some 188 lb (85 kg) less.

By the mid-1970s, the compact V-design (e.g. Buick 231) led to inline-six engines being phased out in passenger cars, but they continued to be installed in trucks and vans until 1988. It is common to find a Buick 3.8 and/or Chevrolet 4.3 in a mid-1980s GM RWD passenger cars with an elongated fan shroud since the motor's positioning is farther back than the inline six.

Overseas, the third-generation of the inline six was mass produced in Brazil. It was used in the Chevrolet Opala from 1969 (230) to 1992 (250). It was already used in light trucks as the A and Chevrolet Veraneio. The Brazilian version of the GMT400 – the Brazilian Chevrolet Silverado – is powered with a 4.1 instead of the Vortec 4300 V6. These inline sixes and their four-cylinder siblings were converted for marine usage by Volvo Penta, and also used in stationary applications (such as power generation) and in Clark forklifts.

153 and 181 four cylinder

The 153-cubic-inch (2.5 L) 153 was a straight-4 version of the family and was only used by Chevrolet with the entry-level Chevy II/Nova. Usage of the 153 lasted until 1970 when the inline six was made the base powerplant with the Chevy II/Nova. Buyers opted for the inline sixes - the 230 or 250. Currently, descendants of the 153 are used with industrial (forklifts or generators) or marine applications. A later variant of the 153, the 181, used a larger 4 inch bore and a longer 3.6 inch stroke. The 181 (branded by GM as the Vortec 3000 for marine or industrial usage) was not installed in passenger cars. This engine is entirely different from the later 151-cubic-inch (2.5 L) Iron Duke, but the two are often confused today. That name was never used for this engine when it was produced.


  • 1962-1969 Chevy II
  • 1967-1971 Postal Jeep
  • 1968-1975 Chevrolet Opala (Brazil)


    The 194-cubic-inch (3.2 L) 194 was shared between Chevrolet and GMC trucks.


  • 1962-1967 Chevy II
  • 1962-1974 Chevrolet 400 (Argentina)
  • 1962-1974 Chevrolet 400 Special (Argentina)
  • 1968-1974 Chevrolet 400 Rally Sport (Argentina)
  • 1964-1967 Chevrolet Chevelle
  • 1965-1966 Studebaker Commander, Daytona ('66 only), Cruiser and Wagonaire (built by McKinnon Industries in Canada)


    Pontiac had a 215 that was used from 1964 to 1965.


    The 230 replaced the 235 cubic inches (3.9 L). It was also used by Chevrolet and GMC trucks, primarily the half-tons. For 1937 and 1938, GMC used Oldsmobile's 230. It produced 140 hp (100 kW). The 230 had a firing order of 1-5-3-6-2-4 rotating clockwise.

    This engine was used on the following vehicles:

  • 1964 Chevrolet Chevelle
  • 1965-1968 Checker Marathon
  • 1965 Chevrolet El Camino
  • 1966-1970 Chevrolet Nova
  • 1966 Studebaker Commander, Wagonaire, Daytona and Cruiser
  • 1967 Chevrolet Chevelle
  • 1967 Chevrolet Camaro
  • 1962-1974 Chevrolet 400 Special (Argentina)
  • 1964-1974 Chevrolet 400 Super (Argentina)
  • 1972-1974 Chevrolet 400 Rally Sport (Argentina)
  • 1968 Chevrolet Chevelle Malibu
  • 1969 Chevrolet Camaro
  • 1969 Chevrolet Chevelle
  • 1968-1970 Chevrolet Opala (Brazil)

    Pontiac 3.8

    The Pontiac 3.8 was a special SOHC version of the standard 230-cubic-inch (3.8 L) I6. An optional W53 version on the Firebird produced 215 hp (160 kW).

    This engine was used on the following vehicles:

  • 1967 Pontiac Firebird
  • 1967 Pontiac Tempest Sprint coupe


    The stroked 250 version produced 155 hp (116 kW) for Chevrolet and GMC. Between 1975 - 1984, an integrated cylinder head was produced, with one-barrel intakes for passenger cars, and two-barrel intakes for trucks after 1978.

    During the mid-1970s, the Buick 231 and Chevrolet V6-90 (basically a variant of the Chevrolet small block V8) was replacing the Chevrolet 250 for use in passenger cars and light duty trucks/vans. Passenger car use of the 250-cubic-inch (4.1 L) engine was discontinued after the 1979 model year for North America (along with the Chevrolet 292) since the six was restricted to light truck usage (the 4.1 was discontinued after 1984 in North America where the Vortec 4.3 V6 became the base motor). Brazil held on to the 250 (Known as the 4.1 there) until 1998 when the Chevrolet Omega A was replaced by rebadged Australian Holdens. It would be GM's final inline six until the introduction of the GM Atlas engine in late 2001.

    This engine was used on the following vehicles:

  • 1966-1984 Chevrolet (passenger cars to 1979, trucks/vans to 1984)
  • 1968-1974 Chevrolet 400 Super Sport (Argentina)
  • 1972-1974 Chevrolet 400 Rally Sport (Argentina)
  • 1968-1976 Pontiac Firebird
  • 1968-1970 Pontiac Tempest
  • 1968-1976 Pontiac LeMans
  • 1968-1969 Buick Special
  • 1968-1972 Oldsmobile F-85
  • 1975-1976 Oldsmobile Cutlass
  • 1971-1975 Pontiac Ventura
  • 1968-1971 Buick Skylark
  • 1968-1979 Chevrolet Camaro
  • 1969-1979 Checker Marathon
  • 1971-1992 Chevrolet Opala (Brazil)
  • 1998-1999 Chevrolet Tahoe (Argentina)
  • 1995-1998 Chevrolet Omega A (Brasil)
  • 1998-2001 Chevrolet Silverado - (GMT400) (Brasil)


    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.,/p>

    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, and have no relationship with GM own Rochester Quadrajet carburator, found on various GM 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.

    The 250-S has 171 Horsepower and 229.7 lb.-ft. at 2,400 rpm. It was in the following vehicles:

  • 1974-1980 Chevrolet Opala SS (Brazil)
  • 1977-1980 Chevrolet Opala Caravan SS (Brazil)
  • 1981-1988 Chevrolet Opala - All Line (Brazil)


    The L22 was a 250-cubic-inch (4.1 L) I6 engine produced from 1967 to 1979. The 1978 Camaro had 105 horsepower (78 kW) and 190 ft·lbf (260 N·m) of torque with the 250.,/p>


    The LD4 was a 250-cubic-inch (4.1 L) I6 engine produced strictly in 1978.


    The LE3 was a 250-cubic-inch (4.1 L) I6 engine produced from 1979 to 1984.


    The 292 was only used in Chevrolet and GMC trucks. The block deck is taller, and has a relocated passenger-side engine mount. These were produced between 1962 to 1990. Production of the engine shifted to Mexico after 1984.


    The L25 was GM's "last" pushrod straight-6 engine. It was produced from 1977 to 1988. It was used in Chevrolet trucks. Displacement was 292 cubic inches (4.8 L) and produced 115 hp (86 kW) and 215 ft·lbf (292 N·m). This engine was commonly used in UPS trucks through the 1980s before being replaced by the 4.3L 90 degree V6.

    GMC engines

    GMC as a marque only had a few engine designs, the straight-6, a V8, and a V6 which was also available as a V12 for a brief period. GMC used many engines from other GM divisions, as noted below.


    GMC replaced the Pontiac 223 with their own 228-cubic-inch (3.7 L) 228 in 1939. This overhead-valve engine was produced through 1953. This is the smallest low-deck engine. Bore was 3-9/16" (3.5625") with 3-13/16" (3.8125") stroke. Connecting rod length was 7.000".


    GMC also developed an OHV/pushrod engine in 1939. The 236-cubic-inch (3.9 L) 236 was the first, lasting through 1955. This is a low-deck engine. Bore was 3-5/8" (3.625") with 3-13/16" (3.8125") stroke. Connecting rod length was 7.000"


    In the years of 1939 to 1955, GMC produced a 248-cubic-inch (4.1 L) engine. The 248 was similar to the 236. This is the largest low-deck engine. Bore was 3-23/32" (3.71875") with 3-13/16" (3.8125") stroke. Connecting rod length was 7.000".


    The 256-cubic-inch (4.2 L) 256 was different from the 236 and 248. It was also an OHV/pushrod engine, and was built for just two years, 1940 and 1941. This is the smallest raised-deck engine. Bore was 3-11/16" (3.6875") with 4" stroke. Connecting rod length was 7.000"


    The last GMC-only straight-6 was the 270-cubic-inch (4.4 L) 270. It was produced from 1941 through 1962 and was an OHV/pushrod engine. This is a raised-deck engine. Bore was 3-25/32" (3.78125") with 4" stroke. Connecting rod length was 7.000".


    The 302 GMC inline six was produced from 1952 to 1960, when it was replaced by the V6. It has a 4.00" bore and 4.00" stroke. Connecting rod length was 7.000". This is the largest raised-deck engine. It was originally designed for the GMC military M135 and M211. It was used in military 2.5 ton trucks with the HydraMatic transmission, however the engine was a sealed engine for snorkel/submersion use, had an electric fuel pump, and other features such as a deep sump oil pan. From 1952-1959, GMC manufactured the civilian 302 engine which was not sealed, had a mechanical fuel pump, and used a "standard" oil pan. This engine is popular with hotrod enthusiasts because it delivers tremendous power for an inline six engine, is truck built with a heavy cast block, and can take quite a bit of abuse.

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