Timing Gear Cover and Oil Seal
Early engines
use
a
black
nitrile
or
a red silicone seal
in a
timing
gear
cover
of
pressed steel.
An
oil
thrower
is used
with
a
nitrile
seal,
but
a spacer is used in place
of
the
oil
thrower
with
the
silicone seal.
The
silicone
seal has a series
of
spiral
grooves
set
into
the
front
face
of
the
main
lip and a
shaft
rotation
arrow
marked
on
the
front
face
of
the
seal.
This
type
of
seal is
known
as a
'Spiroseal'.
There is also a
dust
lip
forward
of
the
main
lip.
Later engines use a red or
brown
silicone
'Spiroseal'
in a
timing
gear
cover
of
cast
aluminium
which
is
dowelled
to
ensure
centralisation
of
the
seal.
The
crankshaft
pulley
has
been
lengthened
and
the
oil
thrower
or
spacer
has
been
removed.
The
latest
engines
have
a
wear
ring
fitted
to
the
crankshaft
pulley
and
use a
black
viton
seal
which
has a larger
internal
diameter.
The
latest
viton
seal is
a
'Spiroseal'
with
a
protruding
dust
lip. For
information
on
fitting
the
oil seal and
timing
gear
cover
refer
to
page J.1.
Piston
Type
Piston Height in Relation to Cylinder
Block
Top Face ...
Bore Dia.
for
Gudgeon Pin
Compression Ring GroOve Width - Top
Compression Ring Groove Width - 2nd
& 3rd
Oil Control Ring Groove - 4th
Piston Rings
Top Compression (marked 'TOP') ...
Second and Third Compression (marked 'BTM')
Fourth Oil Control
Top Compression Ring Width
Ring Clearance in Groove
Second and Third Compression Ring Width ...
Ring Clearance in Groove
Fourth Scraper Ring Width
Ring Clearance in Groove
Ring Gap Top Compression
Ring Gap Second and Third Compression
Ring Gap Fourth Scraper
ENGINES FOR REFRIGERATION
UNITS-R.3
A later controlled expansion piston with a 0.020 in
(0.50
mm)
off-set gudgeon pin has been
introduced
and details of these are given on Pages B3. B.4. F.2
and F.3.
A controlled expansion piston has been
introduced
into the 4.108 refrigeration specification engine. These
pistons have a closer tolerance to the
cylinder
bore.
therefore extreme care must be taken
during
handling.
storing and refitting as any distortion
or
damage
to
the
piston skirt could lead to a seizure.
An
interim controlled expansion piston was
introduced
from Engine No. 108U113592 and a final specification
piston from Engine No. 108U119423. The final specifica-
tion piston will be the only one supplied as a spare
part. and when used as a replacement
for
the interim
or
the
older
type five ring piston. they should only be
fitted in complete engine sets using the
correct
piston
ring pack.
Details
of
the controlled expansion pistons and
their
respective ring layouts are as
follows:
-
Flat Topped - Controlled Expansion
0.002/0.006 in (0,05/0.15
mm)
above
1.0627/1.0629 in (26.994/26.999
mm)
0.080/0.083 in (2,03/2.10
mm)
0.064/0.065 in (1.64/1.65
mm)
0.188/1.189 in (4,79/4,81
mm)
Chrome Plated Taper Faced
Internally Stepped
Spring Loaded
Scraper
0.077/0.078 in (1.96/1,98
mm)
0.003/0.005 in (0.08/0.13
mm)
0.0615/0.0625 in (1.56/1.59 mm)
0.0015/0.0035 in (0.04/0.09
mm)
0.186/0.1865
in
(4.72/4.74 mm)
0.002/0.0035 in (0.05/0.09 mm)
0.012/0.020 in (0.30/0.50
mm)
0.009/0.017 in (0.23/0,43
mm)
0.010/0.018 in (0.25/0,46
mm)
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