Pontiac straight-6 engine

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

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.

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. 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.

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.

The 223 was 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).

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.

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.

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.

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Wikipedia