Pontiac straight-6 engine
Like most American automobile manufacturers, Pontiac relied on the straight-6 design for their circa-World War II automobiles.
"Split Head" Six
186
In the 1920s Oakland Motor Car engineers designed an all new engine for their "companion" make, the Pontiac that was introduced in 1926. It was a side-valve design with a one piece cast iron block with three main bearings. An unusual feature was that it had two separate cylinder heads that each covered three cylinders. The ignition distributor was mounted on top of the block in the gap between the heads.
This engine displaced 186.7 cu in (3.1 L) (3.25x3.75) and was rated at 40 hp (30 kW; 41 PS) @ 2400 rpm when it was introduced. The compression ratio was 4.8-1.[1]
200
In 1929, the "split head" Pontiac six was increased in displacement to 200 cu in (3.3 L). The horsepower rating increased to 60 hp (45 kW; 61 PS) @ 3000 rpm. Compression was increased slightly to 4.9-1.[1] The "split-head" six was discontinued by Pontiac at the end of the 1932 model year. Pontiac offered only eight-cylinder engines during 1933 and 1934.
Flathead Six
208
In 1935, Pontiac re-introduced their six-cylinder engine, as a 208 cu in (3.4 L) straight-6. The 208 was produced in 1935 and 1936. It was a side-valve design with a timing chain, as was popular at the time. This engine featured a conventional one piece cylinder head, and the distributor was moved to the side of the block. The number of main bearings was increased to four. Like the Pontiac Straight-8 engine it also featured full-pressure oiling and insert type precision main and rod bearings. These two latter features greatly increased longevity and durability especially under high speed conditions.
223 Pontiac/GMC
Just as was done with their later V8s, Pontiac shared their mainstream straight-6 engine with GMC for truck use. It was also a side-valve engine, and used a timing chain. The 223 cu in (3.7 L) straight-6 was used in Pontiac automobiles (1937–40) and GMC trucks (1938 only).
239
The 239 cu in (3.9 L) straight-6 was similar in design to previous sixes. It was used from 1941 through 1954 only in Pontiac automobiles.
Specifications
| Year | Model name (number) | Displacement cu in | Output BHP (kW) @ RPM | Torque ft·lbf. (Nm) @ RPM | Compression | Carburetor series (bbl) | |
| 1935 | Master & DeLuxe 6 (6-35) | 208.0 | 80 (58.88) @3600 | 150(203.40) @ 1600 | 6.2-1 | Carter W-1 (1) | [2] |
| 1936 | Master & DeLuxe 6 (6-36) | 208.0 | 80 (58.88 @ 3600 | 150 (203.40) @ 1600 | 6.2-1 | Carter W-1 (1) | [2] |
| 1937 | Six (6-37) | 222.7 | 85 (62.56) @ 3520 | 161 (218.32) @ 1600 | 6.2-1 | Carter W-1 (1) | [2] |
| 1938 | Six (6-38) | 222.7 | 85 (62.56) @ 3520 | 161 (218.32) @ 1600 | 6.2-1 | Carter W-1 (1) | [2] |
| 1939 | Quality & DeLuxe 6 (39-25) & (39-26) | 222.7 | 85 (62.56) @ 3520 | 161 (218.32) @ 1600 | 6.2-1 | Carter WA-1 (1) | [2] |
| 1940 | Special & DeLuxe 6 (40-25) & (40-26) | 222.7 | 87 (64.03) @ 3520 | 164 (222.38) @ 1400 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1941 | Custom, DeLuxe & Streamliner Torpedo 6 (41-24), (41-25), & (41-26) | 239.2 | 90 (73.59) @ 3200 | 175(237.30) @ 1400 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1942 | Torpedo & Streamliner Torpedo 6 (42-25) & (42-26) | 239.2 | 90 (73.59) @ 3200 | 175 (237.30) @ 1400 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1946 | Torpedo & Streamliner 6 (46-25) & (46-26) | 239.2 | 93 (68.45) @ 3400 | 175 (237.30) @ 1400 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1947 | Torpedo & Streamliner 6 (47-25) & (47-26) | 239.2 | 93 (68.45) @ 3400 | 175 (237.30) @ 1400 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1948 | Torpedo & Streamliner 6 (48-25) & (48-26) | 239.2 | 93 (68.45) @ 3400 | 178 (241.37) @ 1400 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1949 | Silver Streak 6 (49-25) | 239.2 | 93 (68.45) @ 3400 | 178 (241.37) @ 1400 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1950 | Silver Streak 6 (50-25) | 239.2 | 90 (66.24) @ 3400 | 178 (241.37) @ 1200 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1951 | Silver Streak 6 (51-25) | 239.2 | 96 (70.65) @ 3400 | 191 (259.00) @ 1200 | 6.5-1 | Carter WA-1 (1) | [2] |
| 1952 | Silver Streak 6 (52-25) with manual trans. | 239.2 | 100 (73.59) @ 3400 | 189 (256.28) @ 1400 | 6.8-1 | Carter WA-1 (1) | [2] |
| 1952 | Silver Streak 6 (52-25) with automatic trans. | 239.2 | 102 (75.07) @ 3400 | 189 (256.28) @ 1400 | 7.7-1 | Carter WA-1 (1) | [2] |
| 1953 | Chieftain 6 (53-25) with manual trans. | 239.2 | 115 (84.63) @ 3800 | 193 (261.71) @ 2000 | 7.0-1 | Carter WCD (2) | [2] |
| 1953 | Chieftain 6 (53-25) with automatic trans. | 239.2 | 118 (86.84) @ 3800 | 193 (261.71) @ 2000 | 7.7-1 | Carter WCD (2) | [2] |
| 1954 | Chieftain 6 (54-25) with manual trans. | 239.2 | 115 (84.63) @ 3800 | 193 (261.71) @ 2000 | 7.0-1 | Carter WCD(2) | [3] |
| 1954 | Chieftain 6 (54-25) with automatic trans. | 239.2 | 118 (86.84) @ 3800 | 193 (261.71) @ 2000 | 7.7-1 | Carter WCD(2) | [3] |
Overhead Valve
In the mid-1960s, Pontiac revived their straight-6 for a short time. Although it was of a different displacement, this Pontiac engine was based on Chevrolet's Generation 3 straight-6.
Pushrod 215
The 215 cu in (3.5 L) straight-6 was produced in 1964 and 1965. It is sometimes confused with the 215 aluminum V8 used in the two years prior. It was an OHV/pushrod engine design, quite different from the previous Pontiac straight-6 engines. It was a smaller bore (3.75") version of the 230 cu in (3.8 L) Chevrolet straight-6 engine. The Pontiac 215 engine had a Chevrolet bellhousing but the flywheel/flexplate bolt pattern had a Pontiac V8 bolt pattern.
Overhead Cam
An overhead cam design was introduced by Pontiac in the 1966 model year. The Pontiac OHC-6 engine shared internal dimensions with the standard 230 cu in (3.8 L) Chevrolet straight-6 engine, but had block and head castings unique to the OHC. Both the head and the block were cast iron; only the large cam carrier/valve cover was aluminum. The engine featured a single overhead camshaft (SOHC) and was the standard engine in the Pontiac Tempest.
The Pontiac OHC-6 engine was considered advanced by Detroit engineering standards at the time. It followed the design of the Jeep Tornado I6, the first post-World War II domestic-developed and mass-produced overhead cam (OHC) automobile engine.[4]
The Pontiac's single camshaft was supported by journals within the aluminum valve cover; no separate bearing shells were used. The cam was driven by a glass fiber-reinforced cogged rubber belt, instead of the usual metal chain or gears. This belt helped to deduce noise. Valves were opened with finger followers (centered under the cam) that pivoted at one end on stationary hydraulic adjusters. The oil pump, distributor drive and fuel pump drive were not within the block, but were handled by an external jackshaft in an aluminum housing that bolted to the right side of the block. The jackshaft was driven by the rubber timing belt. The head had a single port face (exhaust and intake were both on the left side) and the valve stems were strongly tilted towards the left. This engine was used in the 1966 through 1969 Tempest and Le Mans, as well as in the 1967 through 1969 Firebird.
A high-performance version, called the Sprint, was optional. The Sprint featured high-compression pistons, a hotter cam, dual valve springs, a split/dual exhaust manifold, a better coil, and it utilized the then new Quadrajet 4-barrel carburetor.
Like other Pontiac engines of the era, the OHC-6 was not available in Canada with the exception of the Sprint version of the Firebird. Canadian-market Pontiac automobiles were equipped with the Chevrolet OHV six.
The Pontiac OHC-6 engine ended production with the 1969 models.
230
The 230 OHC-6 engine was produced in 1966 and 1967. Power output was rated at 165 hp (123 kW; 167 PS) from 230 cu in (3.8 L). The high-performance Sprint version produced 207 hp (154 kW; 210 PS). The 1967 version of the Sprint produced 215 hp (160 kW; 218 PS).
250
The 250 cu in (4.1 L) replaced the 230 cu in (3.8 L) from 1968 to 1969. The base engine produced 175 hp (130 kW; 177 PS) while the Sprint versions were rated up to 215 hp (160 kW; 218 PS) with automatic transmissions. The versions with a manual transmission received a hotter camshaft that boosted ratings to 230 hp (172 kW; 233 PS).