The cylinders of multi-cylinder automotive engines are arranged in one of three ways.

    1)Inline engines uSe a single black of cylinder. This is the simplest and most common ar-rangement,with all cylinders arranged vertically in line. Most 4-cylinder and 6-cylinder engines are of this design. If an engine has, more than eight cylinders，it becomes diilicult to make a suffi-ciently rigid frame and crankshaft with an in-line arrangement. Also the engine becomes quite long and takes up considerable space.

    2)V-type engines use two equal banks of cylinders，usually inclined 60 degrees or 90 degrees from each other. Most V-type engines have 6 or 8 cylinders，although, V一4 and V-12 engines have been built.

    3)Horizontally opposed or"pancake" engines have two equal banks of cylinders 180 de apart. These space saving engine designs are often air-cooled. This arrangement is used where there is little headroorn,as in trucks，buses，and rail cars.    

    Many parts are also attached by fastening devices to the average block. These items include the water pump，oil pan; timing gear, the flywheel or clutch housing; the ignition distributor, oil and fuel pump,and the cylinder head. The water pump is a component of the'cooling system. The crankshaft usually rotates this unit by means of a belt. When revolving, the water pump circulates coolant between the engine water jackets and the radiator.    

    The cylinder black is cast in one piece. Usually , this is the largest and the most complicated single piece of metal in the automobile. It is made of gray imn ( cast iron)or aluminum and con-fairs the cylinders and the water jackets that surround them. Several engines have aluminum cylin-der blocks. Aluminum is a relatively light metal，weighing much less than cast irpn. However, aiu-minuet is toa soft to use as cylinder-wall material. It wears too rapidly,therefore,aluminum cylin-der blocks must have cast-iron cylinder liners or be cast from an aluminum alloy that has silicon particles in it. The cylinder head closes one end of the cylinder and often contains the valves

through which air and fuel are admitted and the exhaust gases discharged.

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