Chevrolet straight-6 engine
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The Chevrolet straight-six engine was Chevrolet's sole engine from 1929 (when it replaced their 171-cubic-inch (2.8 L) inline-four) through 1954, and was the company's base engine starting in 1955 when they added the small block V8 to the lineup. It was completely phased out in North America by 1990; in Brazil, GM held on to their fuel-injected version through the 1998 model year. It was replaced by more recently developed V6 and four-cylinder engines. Many popular cars and trucks, including the Chevrolet Camaro, Chevrolet Impala, and Chevrolet Suburban used the inline-six as the base engine. Chevrolet did not offer another inline-six until the 2002 General Motors Atlas engine's debut in the Chevrolet TrailBlazer.
|Chevrolet straight-6 engine|
|Manufacturer||General Motors Corporation|
|Production||1929–1990 North America|
2002–2009 (Atlas LL8) North America
2019- (Duramax Diesel)
|Valvetrain||OHV, 2 valves per cylinder|
|Turbocharger||for diesel only|
|Fuel type||Gasoline, diesel|
|Successor||General Motors 90° V6 engine|
Atlas Straight 6
1st Generation (1929 Stovebolt Era)Edit
|Displacement||194 cu in (3.2 L)|
181 cu in (3.0 L)
207 cu in (3.4 L)
|Cylinder bore||3.3125 in (84.14 mm)|
|Piston stroke||3.5 in (88.9 mm)|
3.75 in (95.25 mm)
4 in (101.6 mm)
|Valvetrain||OHV, 2 valves per cylinder|
|Oil system||"splash" lubrication for the rod bearings and pressurized lubrication to the three main bearings.|
|Power output||50 hp (37 kW) 1929–1931 194|
60 hp (45 kW) 1932–1933 194
80 hp (60 kW) 1934–1936 194
"A six for the price of a four"Edit
The first mass-produced GM inline 6 was introduced in 1929 on Chevrolet cars and trucks, replacing the company's first inline-4. Richard Grant (Chevrolet marketing executive) insisted that the new design boast overhead valves, developed by Buick who held the patent for OHV engines and was already building the OHV Buick Straight-6 engine since the early 1910s. Chevrolet had long been known for its "valve-in-head" four-cylinder engines which were also engineered by Buick. William S. Knudsen's cast-iron wonder was produced through 1936.
Toyota's first engine built the similar 206.8 cubic inches (3.4 L) Toyota Type A engine from 1935 to 1947 based on a reverse engineered version of the Chevrolet engine.
It was 193.9 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 × 3.75 in (84.14 mm × 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).
This engine was used in all Chevrolet passenger cars 1929-1933, and the 1934 "Standard" models.
- 1929 Chevrolet Series AC International (Only $10 more than 1928s four-cylinder)
- 1930 Chevrolet Series AD Universal
- 1931 Chevrolet Series AE Independence
- 1932 Chevrolet Series BA Confederate
- 1933 Chevrolet Eagle
A 181-cubic-inch (3.0 L) (3.3125 by 3.5 inches (84.14 mm × 88.90 mm) version was used by Chevrolet in the Master series of cars in 1935 and 1936.
206.8-cubic-inch (3.4 L) (3.3125 by 4 inches (84.14 mm × 101.60 mm)) variant was used by Chevrolet trucks in 1934, 1935, and 1936. The 1934 Chevrolet "Master Deluxe" series used this engine, as did all 1935-1936 Chevrolet passenger cars. This newly revised engine put out 80 hp (60 kW).
Second generation: 1937-1963Edit
The next-generation Chevrolet inline 6 was introduced in 1937 in the US and 1964 in Brazil, and phased out in 1963 in the US, and 1979 in Brazil. It is often known as the "Blue Flame" engine, although that name was only officially applied beginning in 1953, and then only for one certain model of the engine: the 235ci with 3 carburetors applied in Corvettes.
|Displacement||216 cu in (3.5 L) |
235 cu in (3.9 L)
261 cu in (4.3 L)
|Cylinder bore||3.5 in (88.9 mm)|
3.5625 in (90.5 mm)
3.75 in (95.25 mm)
|Piston stroke||3.75 in (95.25 mm)|
3.9375 in (100 mm)
|Valvetrain||OHV, 2 valves per cylinder|
|Compression ratio||6.5:1 |
|Power output||85 hp (63 kW)|
90 hp (67 kW)
92 hp (69 kW)
123 hp (92 kW)
136 hp (101 kW)
150 hp (112 kW)
This engine had a 216.48-cubic-inch (3.5 L) displacement with a bore and stroke of 3.5 by 3.75 inches (88.90 mm × 95.25 mm). A four-bearing crankshaft was added, along with 6.5:1 compression pistons, for 85 hp (63 kW). A new cylinder head in 1941 increased 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 at the connecting rods (which were equipped with "dippers"), thus supplying oil to the rod bearings.
Rod bearings were made of babbitt cast integral with the rod. The bearing was adjustable for wear by removing copper shims placed between the rod cap and connecting rod. In this way specified oil clearance could be maintained. 
This engine was also used in GM's British Bedford truck. In the late 1930s rival Austin decided to get into the 2-3 ton truck ("lorry") market and in a crash program based the design on the basic architecture of this "Stove Bolt" engine, except that they added detachable shell main and con-rod bearings and pressurized lubrication. That Austin engine, in six-cylinder form, post war, went on to power cars such as the Austin Sheerline and Princess, and the Jensen Interceptor and 541. Austin also lopped off two cylinders and in that form various versions, with various capacities, powered cars such as the Austin 16, A70 Hampshire and Hereford, A90 Atlantic, the Austin-Healey 100-4 and the Austin Gipsy, a generation of commercial vans, as well as some models of the iconic London black taxi (FX3 and FX4).
In 1941, a 235.5-cubic-inch (3,859 cc) version of the 216 engine was introduced for use in large trucks. Both the bore and stroke of (3.5625 in × 3.9375 in (90.49 mm × 100.01 mm) were increased over the 216. This engine also had an oil "dipper system" as described above, in reference to the oiling system, as in the 216.
This 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 three-speed manual transmission until 1954, when the 235-cubic-inch (3.9 L) became the standard powerplant on all Chevrolet passenger cars. Two versions were used in 1953 cars - a solid-lifter version called the Thrift-King, with 123 hp (92 kW) for standard transmissions, and the hydraulic-lifter 136 hp (101 kW) version (the Blue-Flame) for Powerglide use. The "Blue Flame" moniker had been used in Chevrolet advertising since 1934. A blue rather than yellow flame within the cylinder meant that perfect combustion was achieved, promised GM's ad men.
From 1954 to 1963, the high-pressure 235 engine with mechanical valve lifters was used in some trucks. From 1956 to 1962, all 235 engines used in cars had hydraulic lifters.
The original 1953 Corvette engine was the high-pressure 235 engine equipped with mechanical lifters. A 150 hp (112 kW) 235 engine was used in the 1954 Corvette and into 1955 (until they were all sold). The Corvette 235 was equipped with the same slightly higher-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 inches (3.9 L) is known as one of the great Chevrolet engines, noted for its power and durability. It was gradually replaced by the third generation 230, beginning in 1962.
Canadian-production GMC trucks used the 216 and 235 Chevrolet straight-six engines as their base light-duty truck powerplant in the late 1940s and early 1950s in Canada, not the United States. The 216 was used from 1947 to 1953, and the 235 was used in 1954 light-duty trucks only. Medium-duty GMC trucks used US built GMC engines in the 248, 270, and up sizes prior to 1954.
In 1954, a 260.9-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 different block casting with a larger piston bore of 3.75 inches (95.25 mm), two extra coolant holes (in the block and head) between three paired (siamesed) cylinders, and a slightly higher lift camshaft. This engine was offered as a step up from the 235 starting in 1954. It was offered in parallel with the GMC V6 engine in 1960 until 1963, when it was discontinued. The 261 US truck engine had mechanical lifters and was available from 1954 to 1962.
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 a standard 261-cubic-inch engine that had hydraulic lifters. This engine was not sold in the US, but was very similar to the US truck 261.
The 261 engines were also used in light trucks and the Chevrolet Veraneio from 1958 to 1979 in Brazil.
Third generation: 1962-1988Edit
|Displacement||194 cu in (3.2 L)|
230 cu in (3.8 L)
250 cu in (4.1 L)
292 cu in (4.8 L)
|Cylinder bore||3.563 in (90.5 mm)|
3.875 in (98.4 mm)
|Piston stroke||3.25 in (82.6 mm)|
3.53 in (89.7 mm)
4.12 in (104.6 mm)
|Valvetrain||OHV, 2 valves per cylinder|
|Cooling system||Water cooled|
|Length||32.5 in (830 mm)|
Chevrolet's third-generation inline six was introduced in 1962 and was produced through 1988. Although the exterior dimensions were similar to previous Chevrolet OHV inline six-cylinders, this generation was lighter and had a different cast-in bell housing pattern it shares with all Chevrolet engines designed and produced after 1954, including the modern LS-series "small-block" and "big-block" V8s.
By the time the third-generation 6-cylinders were being designed and developed, Chevrolet was the most popular brand of vehicles in the world, and sales and production of vehicles and engines were into the millions of units per year with increasing markets for Chevrolet engines both within General Motors and outside the company in the industrial, commercial, agricultural, military, or transportation markets both in the U.S. and worldwide.
There were other major differences between the third-generation 6-cylinder/153 4-cylinder and previous Chevrolet inline OHV engines.
- The crankshafts had 7 main bearings (increased from 4).
- The 230 had the stroke reduced to 3.25 inches (82.6 mm) from the 235's 3.9375 inches (100.01 mm).
- 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.
Two variants of the third generation six were produced - the 194/230/250 cid short deck (used in passenger cars, light trucks, and vans), and the tall deck 292 (used with some light trucks, vans, and commercial vehicles, which retained the dimensions of the previous generation "stovebolt" engine).
The first use was in the newly introduced 1962 Chevy II; the following year, Chevrolet passenger cars adopted it (alongside Checker Marathons since 1965) and used this it until 1977 (1979 for Camaros, Novas, and full size Chevrolets). Chevrolet/GMC trucks, which previously used the stovebolts (235 and 261), also used some members (with the tall deck 292 with both the light duty and medium duty trucks, C40-C60) of this family from 1963 through 1984 (short deck motors), as did Pontiac in 1964 and 1965. A 153-cubic-inch (2.5 L) inline-4 version of this engine was 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), 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. Sidenote: the base six cost about US$334 less than a V8, and weighed some 188 lb (85 kg) less.
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. 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. [dubious ] Aftermarket port fuel injection and re-engineered cylinder heads have been the norm although parts for the six e.g. aftermarket intake manifolds (from a three-carburetor setup or a single 4-barrel carburetor), exhaust headers, and/or hybrid cylinder heads based on the small block are costlier than the Small Block Chevrolet, unlike the rival AMC inline six (which has a cult following with Jeep enthusiasts, especially with the 4.0 L). Besides Brazil, the six was also manufactured in Argentina and South Africa.
The 194 or 3.2 L (3,185 cc) was shared between Chevrolet and GMC trucks. Bore and stroke are 3.5625 in × 3.25 in (90.49 mm × 82.55 mm). Within Chevy trucks it was standard in the 1964 to 1966 G10 1⁄2-ton vans. It was not available in the C/K10 1⁄2-ton trucks. In the G10 vans it was rated at 120 hp (89 kW) gross and 177 lb⋅ft (240 N⋅m) gross of torque. General Motors' Argentinian subsidiary also developed a 109.7 cu in (1,797 cc) four-cylinder version called the "Chevrolet 110" for their Opel K 180 compact car.
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-6 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 230 or 3.8 L (3,768 cc) replaced the long-stroke, second generation 235 cu in (3.9 L) version. Bore and stroke are 3.875 in × 3.25 in (98.4 mm × 82.6 mm). It was also used by Chevrolet and GMC trucks, primarily for the half-tons. It produced 140 hp (104 kW). 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, as the Chevrolet "153 cu in (2.5 L)" engine.
The stroked 250 version produced 155 hp (116 kW) for Chevrolet and GMC, with a bore and stroke of 3.875 in × 3.53 in (98.4 mm × 89.7 mm). 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), with one-barrel intakes for passenger cars, and two-barrel intakes for trucks after 1978. The "integrated" cylinder head and intake manifold claimed to have resulted in increased low end torque and fuel economy inclusive of a smoother operation which pre-dated NVH (noise, vibration, and harshness). Some pundits consider the integrated cylinder head as a relic of the malaise era when it was phased out of production in 1984 prior to the introduction of the 4.3 L where it was common to swap the earlier head (or one from the tall deck 292) in place of the integrated head since the extra weight resulted in warpage - especially with light truck and van use including fleets.
During the mid-1970s, the Buick 231 and 4.3 L V6, essentially a 350-cubic-inch (5.7 L) Chevy small-block V-8 with the two rear cylinders removed, were replacing the Chevrolet 250 for use in passenger cars and light duty trucks/vans. Passenger car use of the 250 cu in (4,093 cc) 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 L V6 became the base engine). Brazil held on to the 250 (known as the 4.1 there) until 1998 for passenger cars, when the Chevrolet Omega A was replaced by rebadged Australian Holdens. It was used in Brazil until 2001 in Chevrolet Silverado when the engine line was discontinued. The Brazilian produced sixes gained multipoint fuel injection, distributorless ignition system and redesigned cylinder heads which had smaller intake ports.
It would be GM's final inline six until the introduction of the GM Atlas engine in late 2001. It was also used for a number of large sedans by Chevrolet of South Africa.
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 almost one liter larger in displacement. It took 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, to pressure GMB to field a more powerful racing engine.
By coincidence, engine development manager Roberto B. Beccardi was working on this engine hop-up project out of his own initiative, but lacked factory support or 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 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 250-S has 171 hp (128 kW) and 229.7 lb⋅ft (311 N⋅m) at 2,400 rpm.
The L22 was a 250-cubic-inch (4.1 L) Inline-six engine produced from 1967 to 1979. The '78 Camaro had 105 hp (78 kW) and 190 lb⋅ft (258 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-cubic-inch (4.8 L) engine was used in Chevrolet and GMC trucks as well as some full-sized Chevrolet cars beginning in the early 1960s; the block deck is taller, along with a relocated passenger-side engine mount. 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 "L25". The 292 retained the separate intake (with a Rochester Monojet carburetor) and exhaust manifolds as used with the short deck motors (194-250). It was GM's last pushrod straight-six engine used from 1963 to 1988 in Chevrolet trucks, including UPS truck chassis. Outputs in 1988 (only): 165 hp (123 kW) at 3,800 rpm and 280 lb⋅ft (380 N⋅m) at 1,600 rpm.
Eventually the L25 was replaced by the 4.3 L 90-degree V6.
GMC as a marque really only produced a few engine designs, the straight six, 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 OHV (overhead valve) engine was produced through 1953. With a cylinder bore of 3.5625 inches (90.49 mm), this is the smallest low-deck engine. All four low-deck engines have a stroke of 3.8125 inches (96.84 mm) and used 7 inch long connecting rods.
The 236-cubic-inch (3.9 L) 236 was introduced in 1941. This is a low-deck engine. The bore was 3.625 inches (92.1 mm).
The 248-cubic-inch (4.1 L) 248 was released in 1939 alongside the 228. The 248 was similar to the 236. The bore was 3.71875 inches (94.456 mm). Stroke is 3.8125. Power in 1955 listed as 100 HP @ 3100 rpm; torque 202 lb ft @ 1000 rpm. The 248 was discontinued in 1955.
The 256-cubic-inch (4.2 L) 256 was similar to the 236 and 248. It was also an OHV/pushrod engine, and was built for just two years, 1940 and 1941. This is the largest low deck engine. Bore was 3.78125 and stroke was 3.8125. Power listed as 91 Net HP @ 3000 rpm; torque 201 Net lb ft @ 1000 rpm. Not listed after 1942.
The last GMC-only straight six was the 270-cubic-inch (4.4 L) 270. It was produced from 1941 through 1963, and was an OHV/pushrod engine. This is a raised-deck engine. The bore was 3.78125" (same as 256) and stroke was 4 inches (101.6 mm). Power listed in 1963 as 133 HP @ 3600 rpm; torque 244 lb ft @ 1300 rpm.
The 301.6-cubic-inch (4.9 L) GMC inline six was produced from 1952 to 1960, when it was replaced by the V6. It has a square bore/stroke ratio of 4 by 4 inches (101.6 mm × 101.6 mm). This is the largest raised-deck engine. It was originally designed for the GMC military M135 and M211. It was used in military 21⁄2-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 to 1959, GMC manufactured the civilian 302 engine, which was not sealed, had a mechanical fuel pump, and used a "standard" oil pan. Power listed in 1959-160 HP @ 3600 rpm; torque 268 lb ft @ 1600 rpm. This engine was popular with hotrod enthusiasts because it delivered tremendous power for an inline six engine at the time (although now obsolete), is built with a heavy cast block, and can take quite a bit of abuse.
The 425.6 cubic inches (7.0 L) with a bore and stroke of 4.25 by 5 inches (108 mm × 127 mm) GMC inline six appeared in 1940s 4x4 Cab Over Engine (COE) trucks made in Pontiac, MI. Power ratings for 1955 were 190 HP @ 3200 rpm; torque 350 lb ft @ 1000 rpm. It also appeared in large GMC trucks in the 1950s ending in 1955.
The 502.7-cubic-inch (8.2 L); 4 9⁄16 by 5 1⁄8 inches (115.9 mm × 130.2 mm) GMC inline six was more numerous than the 426 inline six, starting in 1952 and ending with the 1959 model year. In the 1957-1959 model years this engine was listed as 225 HP@3200 rpm and 436 lb ft torque @ 1200 rpm. The GMC 630, 660, 720, and 750 Series of the 1950s offered the 503.
Isuzu 6H EngineEdit
The Isuzu 6H engine is installed in GM medium-duty trucks as the Duramax LG4.
In 2018 Chevrolet showed off a 3.0 liter turbocharged Diesel I6 engine concept in a 2019 Chevrolet Silverado. Starting in the 2020 model year, the LM2 engine is available in the light-duty Chevrolet Silverado.
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- Sheridan's 1946 Chevy Truck — 1941–46 Chevrolet truck photos; much information.
- Stovebolt.com — Online information resource and discussion forums for pre-'73 Chevrolet & GMC trucks.
- 67–72chevytrucks.com — Founded for the 67-72 trucks, it is now an online forum community devoted to all years & models full size Chevy/GMC Trucks. From stock originals, to mud trucks, to show stoppers… our members have them all.
- chevytrucks.org — Specializing in information on 1941–59 Chevrolet trucks; how-to articles, pictures, history, etc.
- "The Art Deco Series" — This site is dedicated to the history and preservation of the Chevrolet & GMC commercial haulers that were produced just before, during, and just after World War II, 1941–46.
- OldTruckNetwork.com — The No. ? online information resource for old trucks and politics.