RUNNING INSTRUCT
ION
S
Towing-eyes
If
it is necessary to tow a vehicle, use the towing-eyes provided.
High-compression engine (8·9 : 1)
This engine is a highly developed unit and it is essential that you should know
something about the specialized maintenance it requires if you are to maintain
it at the peak of its mechanical efficiency. Special recommendations on the
sparking plugs, ignition settings,
and
fuel to be used are given by the manu-
facturers,
and
it is stressed
tha
t failures are bound to occur if these are
not
strictly adhered to.
Part
icular care is needed with this engine owing to its high
compression ratio, which
mak
es it extre mely sensitive to variations in fuel,
ignition timing,
and
the heat range of the parking plugs.
In
lower-compression engines a much wider ran ge of fuels can be tolerated
without causing serious damage to the engine,
and
ignition settings will stand
variations of a reasonable
amou
nt. Also, even if the incorrect sparking plugs
are used, no more damage may be incurred than burnt-o ut plugs or leaky valves.
But
with an engine having a very high compression ratio the range of fuels,
sparking plugs, and ignition settings is much narrower
and
it is essential
that
the
mixture should always be correct, and particularly never overweak at maximum
load
or power.
High-compression engines are very sensitive to variations in spark advance
(over-advance)
and
to fuel/air ratio (mixture). Variations in these settings will
increase the combustion temperature, and if the variation is excessive pre-
ignition will cause high shock waves, resulting in damage to the engine.
The
engine should be deca
rbon
ized at regular intervals as excessive deposits
of
ash from the combustion of lubricating oil
and
fuel can cause pre-ignition
difficulties.
Choice of fuel
When fitted with H.C. engine (compression ratio 8·9 : 1)
The
octane number of a
motor
fuel is an indication given by the fuel tech-
nicians of its kno ck resistance. High-octane fuels have been produced to im-
prove the efficiency of engines by allowing them to operate on high compression
ratios, resulting in better fuel economy
and
greater power. Owing to the
high
compression ratio
of
the 'engine, fuels with an octane rating below 98 are not
suitable; should it be necessary to use a fuel with a lower octane number, the
car must be used very carefully until the correct fuel can be obtained.
It is necessary to use Super grade fuels in the 100-octane
ran
ge unless premium
fuels of minimum 98-octane (Research method) are available.
When fitted with L.
C. engine (compression ratio 8·1 : 1)
Premium fuels of minimum 93-octane (Research method) up to 97-octane are
required, with preference to 95/97.
Super grade fuels
i?
the lOO-octane range can be used if preferred.
20
IGNITION
Static ignition timing
The point where ignition should start is given in
'GEN
ERAL D '1' '. With
the crankshaft stationary at this position the contact breaker points should be
just beginning to open. When the engine is running timing is varied by a centri-
fugal advance mechanism
and
a vacuum control.
Checking static ignition timing
The information given below describes a method of checking the ignition
timing; it does not detail the resetting of the timing when the distributor has
been removed from the engine.
Check
that
the contact points are set to the correct gap when on the
peak
of
the distributor cam (see page
46).
The rim of the crankshaft pulley has a s
ma
ll groove which will correspond
with the long pointer on the timing cover when Nos. 1
and
4 pistons are at
T.D.C.;
the other two pointers indicate 5° and 10° B.T.D.C. To turn thepulley
The knurled nut on the
distributor illustrated to-
gether with the crankshaft
pulley groove and timing
cover pointers
to the required position, remove the sparking plugs, engage
top
gear,
and
push
the car forward until the groove in the pulley is in the correct position (see
'GENERAL
DATA').
With the crankshaft in this position the contact points should be
just
about
to
open.
If
the points are open,
turn
the knurled
nut
towards'R'
until they are
closed;
if they are closed,
turn
the
nut
towards '
A'.
In
both
cases
turn
the
nut
until the points are
just
parting.
A simple electrical method may be used to ensure an accurate check. Connect
a 12-volt bulb between the low-tension terminal on the side of the distributor
and
a good
earth
point on the engine. Switch on the ignition. If the bulb lights,
turn
the knurled
nut
towards
'R'
until the light goes
out
and
then back towards
'A'
until it
just
lights. This will give the correct static timing.
If
thi§adjy§tmsnt
cannot
be
mage
with
th~
kfiYr!
~g
nut
, gQn§y!t ¥QYf !?!§tfi-
butor/Dealer.
21
To Next Page
Loading...
Need help?
General
