ENGINE
helical gear when the shaft
will
engage
with the oil pump.
(c)
Having refitted the cylinder head and
rocker shaft it is advisable to apply oil
to the ground surfaces where the
rockers contact the valves, as these
points do not immediately receive a
supply of oil.
11.
TO SET
VALVE
CLEARANCES
111
All adjustments should be made when the
engine is cold.
(a)
Remove the rocker cover from the
engine.
(b)
Turn the engine over by hand until
the valves of any cylinder are on the
point of rock. Note the number of this
1
cylinder.
(c)
Continue turning the engine for
another complete revolution, this
will
ensure that the tappets of this cylinder
I
are at the base of the cam (Fig.
23).
Fig.
23
Tappet on base or concentric position
(d)
Holding the ball pin in the rocker arm
of cam.
with a screwdriver, loosen the lock nut.
(e)
Pressing down on the screwdriver to
12.
TO
SET
VALVE
TIMING
IN
THE
eliminate any slackness in the valve
ABSENCE OF
TIMING
WHEEL
gear.
MARKINGS
(f)
Turn the screwdriver until a feeler
It is assumed that, for the purpose of this
gauge of
.010"
for inlet valve or
,012"
instruction, the cylinder head and valve
for exhaust valve will pass between the
gear are in position and the crankshaft
toe of the rocker and the tip of the
sprocket is keyed to the crankshaft but the
valve stem. The ball pin or screwdriver
camshaft chainwheel has yet to
be
fitted.
is turned anti-clockwise to increase the
The following procedure is recommended
:
gap and clockwise to decrease the gap.
(a)
Set valve rocker clearances for Nos. 1
(g)
Holding the screwdyiver steady, tighten
and 4 cylinders to .015" which is the
the lock nut.
Still
applying pressure to
valve timing clearances.
the heel of the rocker check the gap and
(b)
Turn crankshaft until Nos. 1 and 4
adjust if necessary.
pistons are at
T.D.C.
(h)
Repeat with the second valve of that
This position may be found by placing
cylinder.
the keyway in the crankshaft vertically
(i)
Having noted the number of this downwards.
cylinder continue with the remaining
(c)
Rotate the camshaft until the exhaust
three in the firing order 1,
3,
4, 2, by
valve and inlet valve of No. 4 cylinder
turning the engine half a revolution
are at the point of balance in which the
before making adjustments.
tappets
will
be
in the position shown
(j)
Replace the rocker cover pressing, en-
in
Fig. 24. In this position the exhaust
suring first that the cork seal is in
valve
will
just be about to close and the
sound condition and second, when inlet just commencing to open. From
placing the cover in position, that the the timing diagram, Fig. 25, it
will
be
right-hand side does not foul the com- observed that the inlet valve opens at
bustion head securing nuts. Failure to 15" B.T.D.C. and the exhaust valve
observe either of these points may
closes at
15" A.T.D.C.
15"
before or
result
in
a
serious loss
of
oil. &!er T.D.C. is equivalent to .081"
22
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