Chevrolet Straight-6 engine

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Straight 6
ManufacturerGeneral Motors Corporation
Production1929 - 1990
SuccessorGM Atlas engine

The Chevrolet inline 6 of the 1930s through 1970s was the base engine in many popular cars, including the Chevrolet Camaro.

1929 Stovebolt Era

First Generation
Production1929 - 1936
Bore3.3125 in (84.1 mm)
Stroke3.75 in (95.3 mm)
Displacement194 cu in (3.2 L)
Power output50 hp (37 kW)

The first mass-produced GM inline-6 was introduced in 1929 on Chevrolet cars and trucks, replacing the company's inline-4. It was produced through 1936.


It was 194 cubic inches (3.2 L) in size and produced 50 hp (37 kW). This engine used a forged steel crankshaft with three bearings and cast iron pistons. Bore and stroke was 3.3125 in (84.14 mm) by 3.75 in (95.25 mm). The 194 was shared with Chevrolet and GMC trucks for 1935 and 1936.

A balanced crankshaft was introduced for 1932, while a higher (5.2:1) compression ratio upped output to 60 hp (45 kW). A new cylinder head two years later pushed output to 80 hp (60 kW).


A 181-cubic-inch (3.0 L) version was used by Chevrolet and GMC trucks in 1935 and 1936.


A 207-cubic-inch (3.4 L) variant was used by Chevrolet and GMC trucks in 1934, 1935 and 1936.


The next-generation Chevrolet inline 6 was introduced in 1937 and phased out in 1963. Both were also shared with Chevrolet's trucks.


This engine displaced 216-cubic-inch (3.5 L) with a 3.5 in (88.9 mm) bore and the a 3.75 in (95.25 mm) stroke. A four-bearing crankshaft was added, along with 6.5:1 compression pistons, for 85 hp (63 kW). A new cylinder head in 1941 bumped output to 90 hp (67 kW), and 6.6:1 compression gave the 1949 model 92 hp (69 kW). This generation did not use a fully pressurized oiling system.The connecting rods were oiled using an "oil trough" built into the oil pan that had spray nozzles that squirted a stream of oil that the connecting rods (which were equipped with dippers) caught on the fly and supplied the necessary oil for the rod bearings


In 1941, a 235-cubic-inch version of the 216 engine was introduced for use in large trucks. This engine also had a "dipper system" as described above, in reference to the oiling system, as in the 216.

The 235-cubic-inch (3.9 L) version was added to cars in 1950 to complement the new Powerglide automatic transmission, and 3.55:1 rear differential. Hydraulic lifters were used in the Powerglide 235 and a fully pressurized lubrication system was introduced in 1953, but only in cars ordered with the "Powerglide" transmission. The 216-cubic-inch (3.5 L) continued to be standard powerplant for cars with the 3 speed manual transmission until 1954 when the 235-cubic-inch (3.9 L) became the standard powerplant on all its cars. Two versions were used in 1954 cars - a solid-lifter version with 123 hp (92 kW) for standard transmissions and the hydraulic-lifter 136 hp (101 kW) version (The Blueflame) for Powerglide use.

From 1954 to 1962, the high-pressure 235-cubic-inch engine with mechanical valve lifters was used in trucks. From 1956-1962, all 235-cubic-inch engines used in cars had hydraulic lifters.

It is interesting to note that the original 1953 Corvette engine was the high-pressure 235-cubic-inch engine equipped with mechanical lifters. A 150 hp 235 engine was used in the 1954 Corvette and into 1955 (until they were all sold). The Corvette 235 was equipped with the same high-lift camshaft as used in the 261 truck engine and used triple side draft, single barrel, Carter Model YH carburetors mated to a PowerGlide transmission and dual exhaust manifold.

The Chevrolet 235-cubic-inch is known today as one the great Chevrolet engines, noted for its power and durability.


In 1954, a 261-cubic-inch (4.3 L) truck engine was introduced as an optional Jobmaster engine for heavy-duty trucks. This engine was very similar to the 235 engine, except for a larger piston bore, two extra coolant holes (in the block and head) between three paired (siamesed) cylinders, and a higher-lift camshaft. The 261 USA truck engine had mechanical lifters and was available from 1954-62. In 1963, the 261 truck engines was available in 4x4 Chevrolet trucks (until the engines sold out).

The 235 and 261 truck engines were also used by GMC Truck of Canada (GMC truck 6-cylinder engines were also used in Canada). The 1955-1962 Canadian full-size Pontiac car had an optional 261-cubic-inch engine that had hydraulic lifters. This engine was not sold in the USA but was very similar to the USA truck 261.

Generation 3

Third Generation
Production1962 - 1988
Bore3.563 in (90.5 mm)
3.875 in (98.4 mm)
3.875 in (98.4 mm)
3.875 in (98.4 mm)
Stroke3.250 in (82.6 mm)
3.250 in (82.6 mm)
3.530 in (89.7 mm)
4.120 in (104.6 mm)
Displacement194 cu in (3.2 L)
230 cu in (3.8 L)
250 cu in (4.1 L)
292 cu in (4.8 L)
Length32.5 in (830 mm)

Chevrolet's third-generation inline-6 was introduced in 1962 (two years after rival Chrysler introduced its Slant Six) and produced through 1988. This generation was lighter in mass although the dimension were similar to the previous generation Stovebolts - the difference between the Stovebolt and the third generation sixes is the cast-in Chevrolet V8 bell housing pattern (similar to Chevrolet small block, big blocks, and the W-series). With the addition of the bellhousing redesign - transmission bellhousings (for manual transmissions) and automatics between Chevrolet V8s and sixes are interchangeable - this also includes the starter motors between both engines.

There are a few differences - the harmonic balancer received cast-in pulley provisions (for air-conditioned vehicles, a stamped steel pulley was bolted up front), and the rocker arm ratio is close to the one used in the Chevrolet GEN IV big block (1.75:1 ratio).

Although still considered a truck motor, 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.

By the mid-1970s, the compact V-design (e.g. Buick 231) led to the phaseout of inline sixes in passenger cars where the inline six continued for usage 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 at the Chevrolet Opala from 1969 (230) to 1992 (250). It was already used in light trucks as the A and Chevrolet Veraneio (this also includes the Brazilian version of the GMT400 - the Brazilian Chevrolet Silverado is powered with a 4.1 instead of the Vortec 4300). It was already converted for marine usage by Volvo Penta (the 4 cylinder version, the 151 was converted too), at stationary applications (power generation) and at Clark Forklifts.


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 the bore/stroke of the 250. 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.



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


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


Pontiac's 215 (1964-1965) is documented elsewhere.


The 230 REplaced 235 cubic inches (3.9 L). It was also used by Chevrolet and GMC trucks. It produced 140 hp (100 kW). This engine was used on the following vehicles:


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 145 hp (108 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 since the six was restricted to light truck usage (the 4.1 was discontinued after 1984 where the 4.3 V6 became the base motor). It would be GM's final inline six (along with the Chevrolet 292) 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)
  • 1968-1976 Pontiac Firebird
  • 1968-1970 Pontiac Tempest
  • 1968-1976 Pontiac LeMans
  • 1968-1969 Buick Special
  • 1968-1972 Oldsmobile F-85
  • 1975-1976 Oldsmobile Cutlass
  • 1971-1974 Pontiac Ventura
  • 1968-1971 Buick Skylark
  • 1968-1979 Chevrolet Camaro
  • 1969-1979 Checker Marathon
  • 1968-1992 Chevrolet Opala (Brasil)


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


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, along with a relocated passenger-side engine mount. These were produced between 1963 to 1990; production of the engine shifted to Mexico after 1984.


The L25 was GM's "last" straight-6 engine, produced from 1977 to 1988. It was used in Chevrolet trucks, displaced 292 cubic inches (4.8 L) and produced 115 hp (86 kW) and 215 ft·lbf (292 N·m).


Main article: GM Atlas engine

In 2002, GM announced a new family of straight-6 engines, the Atlas. Branded by GM under the Vortec name, the Vortec 4200 or Atlas LL8 is currently the only straight six available to the GM family of vehicles.

See also