(1) LHead. In Lhead engines, both the valves are placed in the block
on the same side of the cylinder. The valveoperating mechanism is located
directly below the valves, and one camshaft actuates both the intake and
exhaust valves. This type has taken place of the Thead, in which both valves
are in the block but on opposite sides of the cylinder. The disadvantage of
the Thead was that it required two complete valveoperating mechanisms.
(2) IHead. Engines using the Ihead construction are commonly called
valveinhead or overhead valve engines. This arrangement requires a tappet,
push rod, and a rocker arm above the cylinder to reverse the direction of the
valve movement, but only one camshaft is required for both valves. Some
overhead valve engines make use of an overhead camshaft. This arrangement
eliminates the long linkage between the camshaft and valve.
(3) FHead. In Fhead engines, the intake valves normally are located
in the head, while the exhaust valves are located in the engine block. This
arrangement combines, in effect, the Lhead and the Ihead valve arrangements.
The valves in the head are actuated from the camshaft through tappets, push
rods, and rocker arms (Ihead arrangement), while the valves in the block are
actuated directly from the camshaft by tappets (Lhead arrangements).
d. Cylinder Arrangement. Automotive engines also vary in the arrangement
of cylinders, depending on the engine use. Cylinder arrangement in liquid
cooled engines is usually inline or Vtype; in aircooled engines, it is V
type, radial, or horizontalopposed.
(1) InLine. The vertical inline cylinder arrangement is one of the
most widely used. All cylinders are cast or assembled in a straight line above
a common crankshaft which is immediately below the cylinders. A variation is
the inverted inline type.
(2) VType. In the Vtype engine, two inline cylinders are mounted in
a "V" shape above a common crankshaft.
(3) Radial Engines. The radial engine has cylinders placed in a circle
around the crankshaft.
(4) HorizontalOpposed. The horizontalopposed engine has cylinders
laid on their sides in two rows, with the crankshaft in the center.