31. The top model was a 148cc four-stroke engine with the company's own overhead valve engine. 32. The overhead valves are pushed by rockers and pushrods. 33. In 1920 Saxon introduced a new model with a 4-cylinder, 45 hp, overhead valve engine. 34. Pontiac also introduced its 151 cubic inch " Iron Duke " 4-cylinder overhead valve engine. 35. The straight-six was a four main bearing 12 overhead valve design with a short stroke. 36. The overhead valve straight-six engine had a cast iron block and an aluminium cylinder head. 37. The engines were overhead valve iron-blocks, for gasoline use. 38. Later versions used 4DR5 and 4DR6 ( J23 turbo ) 2.7 liter overhead valve diesel engines. 39. Every cylinder head has four overhead valves , which are activated by tappets, pushrods and rocker arms. 40. It was superseded by the 23-60 which had an overhead valve engine and four wheel brakes.
