Automotive Systems

Formerly Automotive Systems I

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Arrangement Of Valves


The majority of internal combustion engines also are classified according to the position and arrangement of the intake and exhaust valves, whether the valves are located in the cylinder head or cylinder block. The following are types of valve arrangements with which you may come in contact:

L-HEAD (fig. 2-11)—The intake and the exhaust valves are both located on the same side of the piston and cylinder. The valve operating mechanism is located directly below the valves, and one camshaft actuates both the intake and the exhaust valves.

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I-HEAD (fig. 2-12)—The intake and the exhaust valves are both mounted in a cylinder head directly above the cylinder. This arrangement requires a tappet, a pushrod, and a rocker arm above the cylinder to reverse the direction of valve movement. Although this configuration is the most popular for current gasoline and diesel engines, it is rapidly being superseded by the overhead camshaft.

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F-HEAD (fig. 2-13)—The intake valves are normally located in the head, while the exhaust valves are located in the engine block. The intake valves in the head are actuated from the camshaft through tappets, pushrods, and rocker arms. The exhaust valves are actuated directly by tappets on the camshaft.

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T-HEAD (fig. 2-14)—The intake and the exhaust valves are located on opposite sides of the cylinder in the engine block, each requires their own camshaft.

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SINGLE OVERHEAD CAMSHAFT (fig. 2-15)—The camshaft is located in the cylinder head. The intake and the exhaust valves are both operated from a common camshaft. The valve train may be arranged to operate directly through the lifters, as shown in view A, or by rocker arms, as shown in view B. This configuration is becoming popular for passenger car gasoline engines.

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DOUBLE OVERHEAD CAMSHAFT (fig. 2-16)—When the double overhead camshaft is used, the intake and the exhaust valves each operate from separate camshafts directly through the lifters. It provides excellent engine performance and is used in more expensive automotive applications. fig0211.gif (9537 bytes)


Q6. Other than construction, what three things differ in gasoline and diesel engines?

Q7. What type of cylinder arrangement is used when height is a consideration?

Q8. In a horizontal-opposed engine, the cylinders are arranged at what number of degrees from each other?

Q9. What type of head design has the valves arranged directly over the cylinder?

Q10. What type of head design has exhaust valves located in the engine block?

Published by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy

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