G18 Engine Dismantling/Inspection/Overhaul - Datsun 510 series Workshop Manual

ENGINE
Dismantling
Remove the
engine from the vehicle
as
previously described
and carefully clean the exterior surfaces The alternator distribu
tor and
starter motor
should be removed before
washing Plug
the carhurettor air horn
to prevent the ingress of foreign
matter
Place the engine and transmission
on the
engine carrier ST4797
0000 if available and dismantle
as
follows
Remove the gearbox from the engine Disconnect the intake
manifold
water
hose
the
vacuum
hose and the intake manifold
to
oil separator hose Remove the intake manifold with the
carburettor Fit the engine
attachment ST3720OG18
to
the
cylin
der block and place tre engine
on
the stand ST371
00000
Remove the clutch
@ S sembl y
as
described in the section
CLUTCH
Remove the exhaust manifold and heat baffle plate
Take off the fan blades and
remove
the
water
pump
pulley
and
fan belt Remove the rocker
cover
hose manifold heat hose and
by pass hoses
Remove the
generator
bracket and the oil fIlter Extract the
engine breather assembly
from above Note that the breather
is fitted
to
the guide and is installed with
a
O
ring
which is
pressed
into the cylinder block
Flatten
the 10ckwasher and
unscrew
the crankshaft
pulley
nut
Withdraw the pulley with the puller
ST44820000 if available
but do
not
hook it in the V
groove
of the pulley
Remove the rocker
cover
and take off the rubber
plug
located
on
the front of the
cylinder
head
Straighten
the lock
ing washer and
remove
the bolt securing the
distributor drive
gear
and camshaft
sprocket
to
the camshaft Remove the drive
gear and take off the sprocket See Fig A 3
Remove the
cylinder
head bolts in
reverse
order to
the
tightening
sequence sOOwn in
Fig
A 18 and lift off the
cylinder
head
as an
assembly See
Fig
A 4
Note that in addition
to
the
ten
cylinder head bolts there
are
also
two
bolts securing the
chain
cover
to
the head Invert the engine
and
remove
the oil
sump Remove the chain
cover
and oil flinger Take off the
nut
securing
the oil pump sprocket and withdraw the sprocket with
the chain in
position
as
shown in Fig A5
Remove the oil pump
and
stramer
Note that
two
of the pump
mounting
bolts
are
pipe guides
Remove the
timing
chain crankshaft sprocket chain ten
sioner and chain stop
Remove the connecting rod caps and push the piston and
connecting
rod assemblies
through
the tops of the bores Keep
all
parts
in order
so
they
can
be assembled in their
original posi
tions
Take out the
flywheel retaining
bolts and withdraw the
flywheel Remove the main bearing caps but take
care
not to
damage the pipe guides Lift
out
the crankshaft and main bear
ings noting that the bearings
must
be reassembled in their original
positions
Remove the
piston rings
with
a
suitable expander and
take off the
gudgeon pin clips
The
piston
should be heated to
a
temperature
of 50
to
600 122
to
1400F before
extracting
the gudgeon pin Keep the dismantled
parts
in order
so
they
can
be reassembled in their original positions
Remove the camshaft rocker
ann
shaft and rocker
ann
assemblies from the head
by taking off the
cam
bracket clamp
ing
nuts
It is advisable
to
insert disused bolts in the No 1 and
No 5 bracket holes
as
the
cam
bracket will fall from the rocker
ann
shaft when it is removed Remove the valve
cotters
using
the
special
tool ST47450000 and dismantle the valve assemblies
Keep
the
parts together
so
they
can
be installed in their original
order
ENGINE
Inspection
and Overhaul
Cylinder head and valves
Inspection and overhaul procedures
can
be carried out by
following the instructions previously given for the L14 LI6
and LIB engines noting the following points
Measure the joint face of the cylinder head using
a
straight
edge and feeler gauge The permissible
amount
of distortion is
0 03
mm
0 0012 in
or
less The surface of the head
must
be
reground
if the maximum limit of 0 1
mm
0 0039 in is
exceeded
Oean each valve by washing in
petrol
then
carefully
examine
the
stems
and heads Discard
any
valves with
worn or
damaged
stems
Use
a
micrometer
to
check the diameter of the
stems
which should be 8 0
mm
0 3 15 in
for both intake and exhaust
valves If the seating face of the valve is excessively burned
damaged
or
distorted the valve must
be discarded The valve
seating
face and valve
tip
can
be refaced if
necessary
but
only
the minimum amount of metal should be removed Check the
free length
and tension of each valve spring and
compare
the
figures obtained with those given in Technical Data
at
the end
of this section Use
a
square
to
check the springs for deformation
and
replace
any
spring
with
a
deflection of 16
mm
0 0630 in
or more
Valve
guides
Measure the clearance between the valve guide and valve
stern
The stem to
guide
clearance should be 0 025 0 055
mm
0 0010 0 0022 in for the intake valves and 0 040 077
mm
0 00160 0030 in
for the exhaust valves The maximum clear
ance
limit is 0 1
mm
0 0039 in The valve guides
are
held in
position with an
interference fit of 0 040 0 069
mm
0 0016
0 0027 in and
can
be removed using a
press
and valve guide
replacer
set
ST49730000 under 2
ton pressure
This operation
can
be carried out at
room temperature
but will be
more
effec
tively performed
at
a
higher temperature
Valve
guides
are
available with oversize diameters of 0 2
mm
0 0079 in The
cylinder head
guide bore
must
be reamed out at normal
room
temperature
and the
new
guides pressed in after heating the
cylinder head
to
a temperature
of approximately
800 C 1760F
The standard valve
guide requires
a
bore of 14 0 14 018
mm
0 551 0 5 52
in
and the oversize valve
guide
a
bore of 14 2
14 218
mm
0 559 0 560 in
Ream
out
the bore of the
guides
to
obtain the desired finish and clearance Use the
reamer
set
ST49710000 to
ream
the bore to
8 000 8 015
mm
0 3 150
0 3 156 in The valve seat surface must
be concentric with the
guide
bore and
must
be corrected if
necessary
using
the
new
valve guide
as
axis
Valve
seat
inserts
Check the valve
seat
inserts for signs of
pitting
The inserts
cannot be replaced but
may
be corrected if necessary using
a
valve seat cutter ST49720000
Scrape
the seat with the 450
cutter
then reduce the width of the
contacting
faces
using
the
150 and 600
cutters
for the intake valve inserts and 150
cutter
for the exhaust valve inserts Seat correction dimensions
are
shown in millimeters in Fig A 6
Lap
each valve into its
seat
after
correcting
the
seat
inserts
Place
a
small quantity of fme grinding paste
on
the seating face
of the valve and lap in
as
previously described for the Ll4 LI6
and L 18 engines
S5