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A
THE ENGINE
Section A.37
MODIFIED
ENGINE MOUNTING
Commencing at Chassis No. MGA528, a packing
plate
(Part No.
AHH5896),
together with longer set
screws
(Part No. HZ$0506), is fitted under the
engine
mounting
on
the left-hand
side
only.
This packing plate is introduced to give an increased
clearance
between the starting
d
og
(on
the
crankshaft
pulley)
and
the
steering-rack
housing.
The modificatio
n
can be fitted
to chassis prior to the
one
given
above.
Section A.38
MODIFIED HALF-SPEED SHAFT Ao'ID
OIL PUMP
DRIVING
SPINDLE
In
cases
of excessive wear on the oil
pump
d
riving
spindle
and
half-speed shaft
skew
gearing, a modified
shan (Part No. AEH619) and spindle (Part No.
AEH620)
may
be fitted.
Tbe
number
of teeth on the oil pump
d
riving spindle
has
been increased from I 0 to
II
and
on
the half-speed
shaft
from
9
to
I 0.
This
modification
was
incorporated
from
Engine
No.
315
and also
on Engine No. 313.
The
new
components
can be fitted on earlier
e ngines
provided that they
are
both
fitted at
the
same
time.
Section A.39
MODrFIED
PISTONS
A.t"'D
RI!'\GS
To improve oil consumptio
n,
twin-segment scraper
rings
(Part No.
AEH615)
were introduced at Engine
No
.
446
and
twin-segment
scraper
rings fitted with
expand<r
rings
(Part
No.
AEH672)
at
Engine No. 2057. These
ri
ngs are interchangeable with the micro-land scraper
rings previously fitted.
To
overcome any tendency
to
piston noise, piston
asse.
m blies
(Part
No. AEH640) incorporating new top
rings (Part No.
AEH649)
we
re
fitted at Engine No.
606.
Piston
assemblies,
complete
with
twin-scraper rings,
expander
rings.
and
the
new
top
rings,
are available under
Part
No.
AEH673
and may be interchanged in
set<
of
four with
those originally
fined.
Section A.40
MODIFIED
CRANKCASE
BREATHER
PIPE
A
new crankcase
b reather pipe was
introduced at
Engine No.
657.
The purpose of
this
modification is
to
overcome
any
possibility of oil
leakage
from
the
engine
breather onto
the
exhaust system,
thus causing fumes
to
enter
the
car.
A.l8
Fitting
the
modified breather
pipe (Part No.
AEH628}
necessita
tes
the use of a
new
clip (Part No. IG 1309)
and
a longer
clutch bell housing
bolt
(Part
No.
HBZ0511)
in
substitution for the clip
a
nd
bolt
which previously
secured the
original
breather pipe to the
crankcase.
Fit
the
breather p
ipe
to the vent
pipe
on the
engine
rear
side
cover,
slide
th
e
clip
over the
end
of
the
pipe,
fasten
the clip
to
tbe gearbox mounting plate with
the
longer
bolt specified,
and secure with the existing nut
and
spring
washer.
Section
A.41
MODIFIED TAPPETS
To
increase the
tappet
contact
area
with
the cylinder
head
and
elitninate the
possibility
of tappet
fracture
the
length
of
the
tappets
has
been
increased by ·25 io.
(·635
rom.)
to 1·5
in.
(38·1 mm.).
This modification was
introduced
at Engine
No.
1087.
The
new tappets
(Part
No
.
AEH651
)
may be fitted
to
earlier
engines
in
complete sets of eight.
C
ommencing
at
Engine
N o.
1587,
tappet
bushes have
been
fitted to the
cylinder
head
to reduce tappet
wear
to
a
minimum.
Each bush
is locked
in
the
head
with
a screwed
plug.
Section A.42
MODIFIED TIMING COVER GASKET
To
obviate complete
dismantling
of
the timing
gear
each
time a new
timing
cover
gasket
is fitted, a gasket
that
is panially cut
to
provide
four sections has been produced
under Part Ko.
AEH377.
The
gasket
may be
fitted
in the
same
way
as the
previous
gasket,
or alternatively
any
one or
more
of
the
four
sections
may
be
detached and
used
separately.
Section A.43
ALTERNATIVE
PISTONS
A domed-top piston giving a compression ratio
of
8·3
: I has been introduced for standard
use;
the piston
is
available
under
Pan No. AEHI}90 and must be
operated
with
a static
ignition
setting
of
s•
B.T.D.C.
Pistons
to
Part
No. AEH681 giving a compression
ratio
of 9·9
:
J
a
re
still ava
ilable,
but
their
use
should
be
confi.ned
to
competition
work with 100-octane
fuel
only.
The
static
ignition
setting
for
9·9 :
I compression
ratio
pistons remains at T.D.C.
MGA
OV.in
Cam).
Issue
5.
32403
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