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.
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most popular for current gasoline and diesel engines, it is rapidly being superseded by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.
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.
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.
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.
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.
Questions
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
