Buick straight-6 engine
The Buick straight 6 was an overhead valve straight-six cylinder automobile engine manufactured by Buick from 1914 to 1930. Produced in displacements from, it was initially used exclusively in the Buick Six platform, later in the Buick Master Six and Buick Standard Six. It continued Buick's tradition of almost exclusively using OHV engines since the Model B in 1904. A total of 11 displacement and bore-and-stroke combinations were produced, starting with a produced from 1914-1916.
The engine was cast with three pairs of siamesed cylinders, and combined its starter and generator in a single unit. The and versions had all 6 cylinders in a single casting. All three of these engines lacked a separate cylinder head, with the cylinders and valves combined in a single unit and pistons accessible via the bottom of the unit. Beginning in 1924 all engines had a removable head. In 1925, Buick dropped its inline-4 cylinder powered Buick Four, replaced by the lower priced Buick Standard Six in and displacement through 1928. The high-end Buick Master Six series produced from 1925 to 1928 was a continuation of the earlier 6 cylinder lineup and used the and engines. The Buick Straight-8 engine introduced in 1931 replaced the straight 6 in all models upon its debut, and was the basis of the Holden straight-six motor.
| Production | Engine | Displacement | Bore × Stroke |
| 1914–1916 | 331 | ||
| 1916–1917 | 224 | ||
| 1917–1923 | 242 | ||
| 1924–1925 | 255 | ||
| 1925 | 191 | ||
| 1926–1928 | 207 | ||
| 1926–1928 | 274 | ||
| 1929 | 239 | ||
| 1929 | 309 | ||
| 1930 | 257.5 | ||
| 1930 | 331.4 |