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Studebaker Straight Eight Engines

First Straight Eight, the President:

The first straight eight engine appeared in the President Model FA, January, 1928.  It was designed under the direction of D.G. “Barney” Roos, Studebaker's chief engineer.   Mr. Roos had extensive background in “eights”, coming from stints with Marmon, Locomobile, and Pierce-Arrow, where he designed the Locomobile Junior Eight and the Marmon Little Eight.   The success of the President Eight engine set the trend toward the design and development of smaller eight cylinder engines, the Commander and Dictator Eights.  This engine developed 100 HP at 3,000 RPM, utilizing a 3 3/8 inch bore and a 4 3/8 Stroke, displacing 313.1 cubic inches. The sturdy 2 5/8 inch crank was carried in five main bearings, with connecting rods offset to allow for greater main bearing length.


Late 1928 (FB engine): bore enlarged to 3 ½ inch (336.7 cubic inches) making 109 HP.

1929 - 1930 (Model FH & FE): compression raised to 5.1 to 1, now making 115 HP.   New manifold, carburetor and choke design as well as a new exhaust manifold design.

1931 – 1932 (Model 80, 90, & 91): redesigned to nine main bearings.  A carburetor silencer was added and horsepower was increased to 122.

1933 (Model 92 President Speedway): HP reached 132 at 3.400 RPM.

After 1933, the Big President Eight would no longer be manufactured.


The Commander / President Straight Eight:

1929 – 1930: The Commander Straight Eight engine was a completely new engine design, patterned after it's big brother the President Eight.  It was released in the Model FD Commander.  It had a bore of 3 1/16 inch and a stroke of 4 1/4 inch (250.4 cubic inches), making 80 HP.  It had one refinement, yet to reach it's sibling, the President, it was designed with nine main bearings.


1931, (Model 70 Commander): valve spring dampeners, carburetor silencer, new carburetor, dual intake manifold, and improved torsional vibration dampener.  Horsepower increased to 101.

1932, (Model 71 Commander): no changes to the engine design.

1933, (Model 82 President): in 1933, no Dictator Eight was manufactured, therefore, the Commander Eight used the Dictator engine, except bored out to 4 inches.   This freed up the existing Commander Eight engine ( 3 1/16 x 4 ¼ – 205.4 cubic inches – 110 HP) for use on the Model 82 President.

1934, (Model C President): no engine changes.

1935, (Model 1C President): no engine changes.

1935, (Model 1B Commander): this engine is used for the last time on the Commander, with a cast iron head and compression ratio of 6.0 to 1, making 107 HP.

1936, (Model 2C President): compression ratio increased to 6.5 to 1, Horsepower increased to 115.

1937, (Model 3C President): no engine changes.

1938, (Model 4C President): compression ratio decreased to 6.0 to 1, Horsepower decreased to 110.  The water pump was moved to the front of the engine, driven off the fan pulley.

1939, (Model 5C President): no engine changes.

1940, (Model 6C President): no engine changes.

1941, (Model 7C President): compression ratio increased to 6.5 to 1, Horsepower increased to 117.

1942, (Model 8C President): no engine changes.

After 1942, the Commander / President Straight Eight would never again be manufactured.


The Dictator Straight Eight:

1930, (Model FC Dictator): the Dictator Straight Eight engine was a completely new engine design, patterned after the Commander Eight, but with a shorter stroke.   It had a bore of 3 1/16 inch and a stroke of 3 ¾ inch (221 cubic inches), making 70 HP.


1931, (Model 61 Dictator): improvements in manifolding, and the carburetor, result in 81 HP.

1932, (Model 62 Dictator): horsepower increases to 85.

1933, (Model 73 Commander): as there were no Dictator models manufactured in 1933, the Dictator engine became available for the Commander, which had lost it's Commander engine to the President line.  The stroke was increased to 4 inches (236 cubic inches), making 100 HP.

1934, (Model B Commander): the dimensions and displacement, reverts back to the original Dictator engine (3 1/16 inch bore and stroke of 3 ¾ inch - 221 cubic inches).   Horsepower is raised to 103 by increasing the compression ratio to 6.3 to 1 and using an aluminum cylinder head.

1934 would be the last time the Dictator Straight Eight engine would be manufactured.

Credit:  The information source for this article came from "Studebaker The Complete Story" by William Cannon and Fred Fox.