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B
THE
IGNITION SYSTEM
Fig.
8
.2
Thr
arrows
indit:atr thr fixed
contat:t
platr
srt:~~ring
scrett• and the
adjvsling
natrh
(2)
If
the contacts are
dirty or
pined
they must
be
cleaned
by polishing
them with
a fine
carborundum
stone
and afterwards wiping
them
with
a
cloth
moistened
with petrol
(gaso
line). The
moving
contact
can
be
removed from
its
mounting
in
order
to
ass.
i st
c
leaning. Cheek and
adjust
the contact
~Iter
setting
after
cleaning
the
contacts.
(3)
Chect
that
the
moving arm
is
free
on its pivot.
If
it is •luggish,
remove
the
arm
and polish
the
pi\101
pin
" ith
a
strip
of fine
emery-cloth.
After-
wards dean
ofT
all
trace
of
emery
dust and apply
a
spot
of
clean engine
oil
to
the
top
of
the
pi\'Ot.
The
contact
breaker spring
tension
should
be
between
20
and 24
o:t. (567
and
680 gm:) measured at the
cont:>cts.
•
Section
B.6
Rt:MOVING
AND
REPLACING
TH
E
DISTRIBUTOR
The
d istributor
can
be
removed
and replaced without
interfering
with
the
ignition timing.
p rovided
the clamp
plate
pinch-bolt is
not d isturbed
.
To facilitate the replacement of the distributor remove
the
distributor
cover and
tum
the
engine
O\'C:r
until the
rotor
arm is
in
a
position pointing to
the
segment
for
No.
4
cylinder plug lead to
provide
a
datum
for
replace-
ment.
Disconnect
the
low-tension lead
from
the
terminal
on
the distributor. Disconnect the suction
advance
pipe at
the union
on
the
d
istrib11tor.
Extract
the
two
bolts
securing
the d istributor
clamp
plate
to
the
distributor
housing and
withdraw
the
distributor.
8 .4
To replace
the distributor
insert
it into
tb.e
di.
s tributor
housing
until
tb.e driving dog rests
o
n the distnoutor
drive shaft. The rotor arm should then
be
rotated
slowly
until the driving
dog
lugs
engage with
the drive sbaft
slots,
both
of
which are
offset
to
ensure
correct
replace-
ment.
Tum
the distributor
body to
align the clampin:
plate
holes
with
those
in
the
housi ng.
The remainder
or
the
assembly is
now
in
the
reverse order to
that
o!
removal.
NOTE.-Provid~
that
tbe
crankshaft has not ....,
l1lnled, the
rotor
arm
will he
opposite
the
segment
for
No.4
plug lead. The
high-tension
leads
can
tben be
repla~
..
tlleir
respectite
plug
terminals In tbcorder
of
firing,
i.e. I,
3,
4
,
2,
remembering that the
d~trlbutor
rotation
is 016-
clockwise whEn
viewed
from
abo<e.
Section
B.7
STATIC
IGNITlO~
TIMil'G
The
ignition tisning
must
be
set
to
satisfy the
requm.
ments of
the
grade
of
fuel
used.
(See
'GENERAL
INFORMATION'.)
After timing the
ignition
it
is essential
that the
distributor adv-
..
nce mechanism
be
che<:ked a
s described
in
Section
B.l3.
To set
the
dist.
r ibutor proceed as
follows
:
(I}
Tum
the
crankshaft
in
thedireetionofrotation unta
No.
4
piston
is at
T. D.C.
on its
compression
strol:e.
This
can
best
be
effected
by
turning
the
engin<
and observing
the
valves.
When tbe
valves
m
'rocking'
(i.e. uhaust just dosing and inlet just
opening) on No.
I
cylinder
No.
4
piston is
appro•~
mately at
T. D.C.
on its compression
stroke.
H
Fig.
B.3
When tlu'
.
~ u>a•r
in
the
crankshtift pullry coincitltJ
H'ith the
small
projection
on
the timing
case Nos.
I
and
4
pistons
(Ire
at
T.
D.C.
MGA
(Twin
Com).
Issue
3. 32411)
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