The Pontiac straight-6 engine is a family of inline-six cylinder automobile engines produced by the Pontiac Division of

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in numerous versions beginning in 1926.

"Split Head" Six

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In the 1920s

Oakland Motor Car The Oakland Motor Car Company of Pontiac, Michigan, was an American automobile manufacturer and division of General Motors. Purchased by General Motors in 1909, the company continued to produce modestly priced automobiles until 1931 when the brand ...

engineers designed an all new engine for their "companion" make, the

Pontiac Pontiac may refer to: *Pontiac (automobile), a car brand *Pontiac (Ottawa leader) ( – 1769), a Native American war chief Places and jurisdictions Canada *Pontiac, Quebec, a municipality ** Apostolic Vicariate of Pontiac, now the Roman Catholic D ...

, that was introduced in 1926. It was a side-valve design with a one piece cast iron block with three

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s. 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 was also used in GMC's T-10 and T-11 (their two lightest trucks) beginning in 1928. Development of the engine shared characteristics with the Oldsmobile Straight-6 engine, as GM worked together to develop the engine for Pontiac combined with the resources of GM-Northway Motor and Manufacturing Division. This engine displaced with a bore and stroke of and was rated at at 2400 rpm when it was introduced. The compression ratio was 4.8:1.http://www.Concept Carz.com/vehicle

200

In 1929, the "split head" Pontiac six was increased in displacement to . The horsepower rating increased to @ 3000 rpm. Compression was increased slightly to 4.9:1. 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

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In 1935, Pontiac re-introduced their six-cylinder engine, as a 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 The Pontiac straight-8 engine is an inline eight-cylinder automobile engine produced by Pontiac from 1933 to 1954. Introduced in the fall of 1932 for the 1933 models, it was Pontiac's most powerful engine at the time and the least expensive eight ...

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

The 223 was a side-valve engine, and used a timing chain. The straight-6 was used in Pontiac automobiles (1937–40) and GMC trucks (1938 only).

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The straight-6 was similar in design to previous sixes. It was used from 1941 through 1954 only in Pontiac automobiles.

Specifications

Overhead Valve

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A overhead valve straight-6 was produced in 1964 and 1965 but was not an original Pontiac design. Sometimes confused with the Buick designed and built aluminum V8 that Pontiac had used in the two years prior, the "Pontiac 215" was an adaptation of Chevrolet's

overhead valve An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located be ...

Turbo-Thrift straight-6. Quite different from Pontiac's previous straight-6s, it had a smaller bore than the larger Chevrolet engine and a Chevy bellhousing, but its

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/flexplate bolt pattern was Pontiac's.

Overhead cam

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single overhead camshaft An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion cha ...

(SOHC) design was introduced by Pontiac in the 1966 model year as the standard engine in the

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. Offered also in 1967, the OHC 6 shared internal dimensions with the overhead valve Chevrolet straight-6 engine it was based on, but had unique cast iron block and head castings. Only the large cam carrier/valve cover was aluminum. It used jackshaft (outside of the block) for oil pump and distributor drive. The jackshaft was driven by the fiberglass reinforced timing belt. It was offered with a single one barrel carburetor, rated at . A W53 Sprint version for the Firebird produced up to . Considered advanced by Detroit engineering standards at the time, the Pontiac OHC 6 followed the Jeep Tornado I6 as the second post-World War II domestic-developed and mass-produced overhead cam automobile engine. 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 noise-reducing fiberglass-reinforced cogged rubber belt instead of the usual metal chain or gears. Valves were opened with finger followers (centered under the cam) that pivoted at one end on stationary hydraulic adjusters. The oil pump, distributor, and fuel pump were driven by an external jackshaft powered by a rubber timing belt nestled within an aluminum housing bolted to the right side of the block. The head had a single port face with both exhaust and intake valves on the left side and valve stems strongly tilted towards the left. This engine was used in the 1966-67

and

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and 1967

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. An optional high-performance Sprint version featured high-compression pistons, hotter cam, dual valve springs, split/dual exhaust manifold, stronger coil, and the then new

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Quadrajet The Quadrajet is a four barrel carburetor, made by the Rochester Products Division of General Motors. Its first application was the new-for-1965 Chevy 396ci engine. Its last application was on the 1990 Oldsmobile 307 V8 engine, which was last us ...

carburetor. rated at . Power was increased to in 1967. Like other Pontiac engines of the era, the OHC 6 was not available in

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

with the exception of the Sprint version of the Firebird. Canadian-market Pontiac automobiles were equipped with the Chevrolet OHV six.

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The OHC was enlarged to for 1968 to 1969. The base engine produced while the Sprint versions were rated up to with automatic transmissions. The versions with a manual transmission received a hotter camshaft that boosted ratings to .

References

{{Reflist

External links

Pontiac Overhead Cam SIX Forum Straight-six engines

Straight-6 The straight-six engine (also referred to as an inline-six engine; abbreviated I6 or L6) is a piston engine with six cylinders arranged in a straight line along the crankshaft. A straight-six engine has perfect primary and secondary engine bal ...