The Buick straight 6 was an engine manufactured by Buick from 1914 to 1930 and was exclusively used in the Buick Six platform, then later in the Buick Master Six and Buick Standard Six. They were OHV, like their previous engines, as Buick had been almost exclusively using overhead valve engines since the Model B in 1904. The engine also had the starter and generator in a single unit. The first six cylinders engine was cast in pairs (3x2 cylinders). The 224 and 242 CID did not have a removable cylinder head, meaning the cylinders and valves came off as a unit, (although with the valves in cages, the cages were removable individually), and pistons had to come out of the bottom of the unit as it was removed. This was colloquially called a "jughead" engine, since the jugs (cylinders) came off with the head. Since 1924, all engines had a removable head. They had a displacement ranging from 191 to 331 cu in (3.1 to 5.4 L) depending on year and model. In 1925, Buick dropped the 4 cylinder engine and all Buicks had 6 cylinders. The 4 cylinder series was replaced by the lower priced Buick Standard Six and used the 191 and 207 engines, and the high-end Buick Master Six series was a continuation of the earlier 6 cylinder lineup and used the 255 and 274 engines. The Buick Straight-8 engine replaced the straight 6 across the board in all models, in 1931,^[1] and was the basis of the Holden straight-six motor.^{[citation needed]}