TIMING CASE AND DRIVE - K.7
Adjust the valve clearances to 0.012 in (0,30
mm) cold. Refit the rocker cover together with a
new joint.
7.
Remove the engine from the dismantling stand
and refit to the application.
TIMING
General
As timing gears are employed on the 4.236 marine
engine, the factory setting remains constant. The
following information is given as a general guide during
an engine overhaul. It is well to remember that the
removal of the cylinder head in no way affects either the
fuel pump or valve timing.
Timing Marks
When the engine is originally timed at the factory,
certain marks are stamped on the gears, so that if for
Fig. K.14.
Showing Timing Pin located in Crankshaft Pulley.
any reason the engine timing has to be disturbed, then
to reset to the original timing is quite straight forward.
Timing Pin
A timing pin is fitted at the bottom of the timing case
cover on the starboard side. When it is unscrewed it
locates in a hole machined in the rear face of the
crankshaft pulley, when Nos. 1 and 4 pistons are at
T.D.C. (see Fig. K.14).
Always return this pin. to its normal location
immediately T.D.C. has been determined and before any
attempt is made to turn or start the engine.
To Reset Engine to the Original Timing
Before commencing the retiming procedure it is
assumed that (a) the camshaft, fuel pump and idler
gears have all been removed, and (b) the camshaft is
free to turn by hand. (If the cylinder head assembly is
still in position, it is advisable to remove the atomisers
and rocker shaft to facilitate the retiming operations).
1.
Turn the engine until the keyway in the front of
the crankshaft is uppermost as shown in Fig.
K.4. (This will bring Nos. 1 and 4 pistons to
T.D.C.)
2.
Fit the camshaft gear by drawing it onto its shaft
using the retaining plate and setscrew. Lock the
setscrew with the tabwasher.
3.
Fit the fuel pump gear to the fuel pump drive
shaft ensuring that the dowel is correctly
located. Secure with the three setscrews and
spring washers.
4.
Replace the idler gear as previously detailed so
that the timing marks are all correctly aligned as
shown in Fig. K.4.
5.
Check that the backlash between the timing
gears is within the limits quoted on Page B.8.
NOTE: When the timing has been reset,
great care should be exercised when first
turning the engine, for should the timing be
incorrectly set, even by only one tooth, there
is the possibility that a valve head will strike
the piston crown.
For Checking Fuel Pump Timing, see Page N.6
Checking Valve Timing
To check the valve timing proceed as follows:
1.
Turn the crankshaft until the valves of No. 4
cylinder are 'on overlap'.
2.
In this position set the valve clearance of No. 1
inlet valve to 0.047 in (1,2 mm).
3.
Turn the engine slowly in the normal direction of
rotation until the clearance of No. 1 inlet valve is
just taken up. (In this condition it will just be
possible to rotate No. 1 inlet valve push rod
between the thumb and the forefinger).
