screw in the rocker arm, as shown in figure 3-74. On
engines with stud-mounted rocker arms, make the
adjustment by turning the stud nut.
Valves in Block
This type of valve arrangement is not commonly
seen in the field; however, the adjustment procedure is
described in case you should happen to run across this
Valves within the block are adjusted "COLD"; that
is, recommended valve clearances are provided for a
cold engine. These valves have mechanisms quite
similar to overhead valves. They are adjusted by
removing the side cover plate beneath the intake
manifold on the side of the engine block (fig. 3-75).
Since you must stop the engine to adjust the valves, the
piston in the cylinder must be on TDC of the
You can determine this by
watching the valves of the piston that is paired with the
one that is being set.
As the cylinder that is being
positioned is coming up on the compression stroke, the
paired cylinder is coming up on the exhaust stroke;
therefore, the exhaust valve is open. Just as the exhaust
valve closed and the intake valve begins to open, the
cylinder to be set is on TDC of the compression stroke,
and you can set the two valves. Once the No. 1 cylinder
is positioned, follow through according to the firing
Figure 3-74.Adjusting overhead valves.
Figure 3-75.Adjusting valve in block.
order of the engine, as this makes the job easier and
faster. You may also use this procedure when adjusting
valves on overhead engines.
Hydraulically Operated Valves
On engines with hydraulic valve lifters, it is not
necessary to adjust the valve periodically. The engine
lubrication system supplies a flow of oil to the lifters at
all times. These hydraulic lifters operate at zero
clearance and compensate for changes in engine
temperature, adapt automatically for minor wear at
various points, and provide ideal valve timing.
To adjust hydraulic lifters with the engine off, turn
the crankshaft until the lifter is on the camshaft base
circle (not the lobe). The valve must be fully closed.
Loosen the adjusting nut until you can wiggle the
pushrod up and down. Then slowly tighten the rocker
until all play is out of the valve train (cannot wiggle
pushrod). Repeat the adjusting procedure on the other
To adjust hydraulic lifters with the engine running,
install a special oil shroud or some other device for
catching oil spray off the rocker. Start and run the
engine until it reaches operating temperature. Tighten
all rockers until they are quiet. One at a time, loosen a
rocker until it clatters. Then tighten the rocker slowly
until it quiets down. This is zero valve lash.
OHC Engine Valves
There are several different methods of adjusting the
valves on an overhead cam (OHC) engine. Many are
adjusted like mechanical lifters in a pushrod engine.
The rocker arm adjuster is turned until the correct size
feeler gauge fits between the rocker or cam lobe and the