Pontiac straight-6 engine

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Like most American automobile manufacturers, Pontiac relied on the straight-6 design for their circa-World War II automobiles.

"Split Head" Six[edit]

186[edit]

In the 1920s Oakland Motor Car engineers designed an all new engine for their "companion" make, the Pontiac, which 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 cubic inches (3,059 cc) (3.25x3.75) and was rated at 40 bhp (29.4 kW) @ 2400 rpm when it was introduced. The compression ratio was 4.8-1.[1]

200[edit]

In 1929, the "split head" Pontiac six was increased in displacement to 200.0 cubic inches (3,277 cc). The horsepower rating increased to 60 bhp (44.2 kW) @ 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[edit]

208[edit]

In 1935, Pontiac re-introduced their six-cylinder engine, as a 208-cubic-inch (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[edit]

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-cubic-inch (3.7 L) straight-6 was used in Pontiac automobiles (1937–40) and GMC trucks (1938 only).

239[edit]

The 239-cubic-inch (3.9 L) straight-6 was similar in design to previous sixes. It was used from 1941 through 1954 only in Pontiac automobiles.

Specifications[edit]

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[edit]

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[edit]

The 215-cubic-inch (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 cubic inch Chevrolet inline 6.

Overhead Cam[edit]

Pontiac Overhead Cam Six engine

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-cubic-inch (3.8 L) Chevrolet Straight-6, but had block and head castings unique to the OHC. Both head and block were cast iron; only the large cam carrier/valve cover was aluminum. The engine featured a Single Over Head Cam and was the base engine in the Pontiac Tempest.

The Pontiac OHC-6 engine was considered advanced by Detroit engineering standards at the time. It followed the Jeep Tornado I6 design, 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, making it state of the art for the time, as well as very quiet. 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.

1968 Pontiac OHC 250 1-bbl

230[edit]

The 230 OHC-6 engine was produced in 1966 and 1967. Power output was rated at 165 hp (123 kW; 167 PS) from 230-cubic-inch (3.8 L). The high-performance Sprint version produced 207 bhp (154 kW). The 1967 version of the Sprint produced 215 hp (160 kW; 218 PS).

250[edit]

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).

See also[edit]

References[edit]

  1. ^ a b http://www.Concept Carz.com/vehicle
  2. ^ a b c d e f g h i j k l m n o p q r Motor's Auto Repair Manual, Sixteenth Edition,Motor.,1953
  3. ^ a b Motor's Auto Repair Manual, Motor,1963
  4. ^ "Kaiser Jeep". Ward's Automotive Yearbook - Volume 26: 137. Retrieved 13 March 2013. 

External links[edit]

  • [1] Pontiac Overhead Cam SIX Forum