1977 DATSUN PICK-UP weight

Fresh
air

Blow

by
gas

CHECKING

VENTILATION

HOSE

1

Check
hoses
and
hose
connec

tions
for
leaks

2
Disconnect
all
hoses
and
blow

them
out
with

compressed
air

If

any
hose

cannot
be
free
of

obstructions

replace

Ensure
that
flame

arrester
is

surely

inserted
in
the

hose
between
air

cleaner
and
rocker
cover

CHECKING
EXHAUST

MANIFOLD
HEAT

CONTROL
VALVE

Run

engine
and

visually
check

counterweight
to
see

if
it

operates

properly

I
For

some
time

after

starting

engine
in
cold

weather

counterweight

turns

counterclockwise
until

it
comes

into

contact
with

stopper

pin
installed

to

exhaust
manifold

Counterweight

gradually
moves

down

clockwise

as

engine
warms

up

and
ambient

temperature
goes
higher

around
exhaust
manifold

2

When

engine
speed
is

increased

discharge
pressure
of
exhaust

gases

causes

counterweight
to
move
down

ward

clockwise
Engine
Tune

up

CoOl
1

Oil
level

gauge

2

8affle

pia
te

3

Flame
arrester

4

Filter

5
P
C
V
valve

6

Steel
net

7

Baffle

plate

1fiI

o

EC716

Fig
ET
20
Crankcaae
emi
ion

control8
tem

3
When
heat

control
valve
is
in
the

full

open

position
counterweight

moves
further

clockwise

exceeding
the

position
described

in
1

1
above
and

stops

again
coming
into

contact
with

stopper

pin

ct

t

C

EC245

1

Counterwe
ht

2

Stopper
pin

3

Heat
control

valve

Fig
ET
21
Cold

operation
of
counte

weigh
t

EC246

1

Counterweight

2

Stopper
pin

3
Heat
control
valve

Fig
ET

22
Hot

operation
of
counter

weight

ET

14
2
With

engine

stopped
visually

check

E
F
E

system
for
the

following

items

I
Thermostat

spring
for
dismount

ing

2

Stopper

pin
for

bend
and
count

er

weight
stop
position
for

dislocation

3

Check
heat
control

valve
for

malfunction

due
to
break
of

key
that

locates

counterweight
to
valve

shaft

4

Check
axial
clearance

between

heat
control

valve
and
exhaust
mani

fold
Correct
clearance
is
0
7
to
1
5

mm
0
028
to

0
059
in

5

Check
welded

portion
of

heat

control

valve
and

valve
shaft
for

any

indication
of
crack

or

flaking

6
Rotate
heat

control
valve

shaft

with
a

fmger
and

check
for

binding

between

shaft
and

bushing
in

closing

and

opening
operation
of
heat
control

valve
If

any
binding
is
felt
in

rotating

operation
move
valve
shaft
in

the

rotation
direction
several
times
If

this

operation
does
not

correct

binding

condition
it
is
due

to
seizure
between

shaft
and

bushing
and

exhaust
mani

fold

should
be

replaced
as
an
assem

bly

CHECKING
SPARK

TIMING
CONTROL

SYSTEM

This

system
is

installed
on
non

California
automatic
transmission

models

SPARK
DELAY
VALVE

Automatic
transmission

models

only

This
valve

delays
vacuum

spark

advance

during
rapid
acceleration
it

also
cuts

off
the

vacuwn

spark
advance

imme

iately
upon
deceleration

The

valve
is

designed
for
one

way
opera

tion

and
consists

of
a
one

way
umbrel

la
valve
and
sintered
steel
fluidic

restrictor

Engine
Mechanical

GENERAL
DESCRIPTION

MODEL

L20B
ENGINE

CYLINDER
BLOCK

CRANKSHAFT

PISTON
AND
CONNECTING
ROD

CYLINDER
HEAD
CONTENTS

EM
2

EM
3

EM
3

EM
3

EM
3
CAMSHAFT

VALVE
MECHANISM

CAMSHAFT
DRIVE

MANIFOLDS

out
smooth

dependable

power

The

cylinder
block
is
cast
as
a

single

unit

and

featllres
deep
skirting
This

engine
is

equipped
with
a

single
2

barrel
downdraft
carburetor
that
in

corporates
a

special
device
to
control

emissions
MODEL
L20B

ENGINE

The
L20B

engine
features
O
H
C

valves

wedge
shaped
combustion

chamber
aluminum
head
and
a

fully

balanced
5

bearing
crankshaft
to
turn

Main

specifications

Oisplacemen
t
cc

cu
in

Bore
x
stroke

mm
in

Compression
ratio

Ignition

timing

Degree
B

T
O
C

rpm
MIT

AlT

MIT
Manual
Transmission
EM535

Fig
EM
Cross
sectional
view

L20B

1

952
1191

85

X
86

3
35
x
3
39

8
5

12
750

Non
California

model

10
750

California

model

12
650
in
0
position

AIT
Automatic
Transmission

EM

2
EM
3

EM
3

EM
3

EM
3

CYLINDER
BLOCK

The

cylinder
block
a
mono
block

special

casting
structure

employs
a

five
bearing

support

system
for

quiet

ness

and

higher
durability

The

cylinder
bores
are
surrounded

by
cooling

jackets
and
machined
di

rectly
in
the
block
The
oil

ways
in
the

block

are
arranged
so
that
the

full
flow

oil
filter
is

directly
attached
to
the

right
hand
side
of
the
block

EM536

Fig
EM

2
Cylinder
block

CRANKSHAFT

The
crankshaft
is

a

special
steel

forging
Fully
balanced
it
turns
out

smooth

dependable
power
at

high

speed

The
L20B

engine
uses

eight
balance

weights

Main

bearings
are
lubricated

by
oil

pumped
through
the
main
oil

gallery

and
the
oil
holes
which
run
in

parallel

with

cylinder
bores
There

are

oilways

drilled
in

the
crankshaft
for
the
lubri

cating
oil
The
center
main

bearing
is

equipped
with
thrust
washers

to
take

up
end

thrust
of
the
crankshaft

r

Piston

pin
outside
diameter

Piston

pin
hole
diameter

Piston

pin
to

piston
clearance

I

Interference
fit
of

piston

pin
to

connecting
rod

CONNECTING

ROD

I
If
a

connecting
rod
has

any
flaw

on
either
side
of
the
thrust
face
or
the

large
end

correct
or

replace
it

EM133

Fig
EM
61
Ch

cking
rod

alignment

Connecting
rod

bend

or
torsion

per
100
mm

or
3
94
in

length

mm
in

3

When

replacing

connecting
rod

select
rod

so
that

weight
difference

between
new
and
old

ones
is

within
7

gr
0
25
oz

Do

not
use

a
combination
of
new

and

former

connecting
rod

big
end

nuts
and

connecting
rod
bolts
which

affect

specified
weight
variations

4
Install

connecting
rods
with

bear

ings
on
to

corresponding
crank

pins

and

measure
thrust
clearance

Ifmeas

ured

value
exceeds

limit

replace
Engine
Mechanical

Unit

mm
in

20
993
to
20
998
0

8265
to

0
8267

21

001
to
21
008
0

8268
to
0
8271

0
003
to
0
015

0
0001
to

0
006

0
015

to
0
035
0

0006
to
0
0014

2
Check

connecting
rod
for
bend
or

torsion

using
a

connecting
rod

aligner

If
bend
or
torsion
exceeds
the

limit

q
rrect
or

replace

Standard

Maximum

0
03
0

0012
0
05

0
0020

Fig
EM
62

Checking
big
end

play

Standard

Maximum

Big
end

play
mm

in
0
2

to
0
3

0

0079
to
0
01
18
0
6
0
0236

EM

16
CRANKSHAFT

1

Whenever
crankshaft
is
removed

from

engine
it

should
be

cleaned

thoroughly
in

a
suitable

solvent

After

cleaning
check

crankshaft

journal
and

crank

pin
Jor
score
bias

wear
or

cracks

Rep
air

or

replace
as

required

If

damage
is
minor

dress
with
fine

crocus
cloth

2

Check

journals
and
crank

pins
for

taper
and

out
of

round
with
a
micro

meter

Measurement
should
be
taken

along
journals
for

taper
and
around

journals
for

out
of
round

See

Figure

EM
63
for

detailed
information

If

journals
or
crank

pins
are

tapered

or
out
of
round

beyond
limits

replace

with
a

new
shaft

A
B

Out
of

round

X
Y

Taper
A
B

Unit
mm
in

19
5

0
768

tt
30
27

32

181
1
06
1
260

43

O
l
69

I

E
1

All

main

journa

59
942
to
59
955
All
crank

pm

2

3599
l
2

3604
49
961
to
49

974

o

1
9670
to
1

9675

EM424

Fig
EM
63

Crankshaft
and

journal

dimensions

Fig
EM
68
P14stigage

Note
Do

not
tum
crankshaft
while

plastigage
is

being
inserted

5
Remove

cap
and

compare
width

of
the

plastigage
at
its
widest

part
with

the
scale

printed
in

plastigage
enve

lope

Fig
EM

69

Measuring
bearing

clearance

MEASUREMENT
OF

CONNECTING
ROD

BEARING

CLEARANCE

I

Measure

connecting
rod

bearing

clearance
in
the

same
manner
as
above

Tightening
torque

4
5

to
5
5

kg
m
33

to
40
ft
lb
Engine
Mechanical

Bearing
011
clearance

Standard
Wear
limit

Main

bearing
clearance

mm
in
0
020
to

0
062

0
0008
to
0
0024
0
12
0
0047

Connecting
rod

bearing

clearance
mm
in
0

025
to
0
055

0
0010
to
0
0022
0

12
0
0047

2
If

clearance
exceeds

specified

value

replace
bearing
with
an
under

size

bearing
and

grind
crankshaft

jour

nal

adequately

FiniNG
BEARINGS

Bearings
are
manufactured
with

crush
to

make

bearing
snug
down
into

its

bore
To

measure
this

proceed
as

follows

I
Set
main

bearing
in
main

bearing

cap
recess
or

cylinder
block

bearing

recess

correctly

2
Lock
one
side
of

bearing
and

press
other
side
until

bearing
back

surface
touches
the
recess

Bearing
crush

All
main

bearings
mm
in

All

connecting
rod

bearings
mm
in

4

Handle

connecting
rod

bearing
in
3
Then

measure

bearing
crush
H

with
a
feeler

gauge
See

Figure
EM
70

The
standard

bearing
crush
value
is

listed
below

Weight

H

Fig
EM
70

Checking
bearing
crum

o
to
0
03
0
to

0
0012

0
015
to
0
045
0
0006
to

0
0018

the
same
manner
as
above

Main

bearing
undersize

Unit
mm
in

Bearing
top
thickness
Crank

journal
diameter

1

827
to

1
835
59
942
to

59
955

SID

0
0719
to

0
0722
2

3599
to
2

3604

0
25
0
0098

1
952
to
1
960

59
692
to

59
705

Undersize
0
0769
to
0
0772
2

3501
to
2
3506

0
50
0
0197
2
077
to

2
085
59442
to
59
455

Undersize
0

0818
to
0

0821
2
3402
to

2
3407

0
75
0
0295
2
202
to
2
210

59
192

to
59
205

Undersize
0
0867
to
0
0870

2
3304
to
2
3309

EM

18

Engine
Fuel

1
L

if

1

Pump
injector

2
Piston

3

Spring

4

Weight

5

Damper
spring

6
Piston
return

spring

7

Inlet
valve

8
Outlet
valve

EF023

Fig
EF
26
Acceleration

mechanism

Power

valve
mechanism

SECONDARY
SYSTEM

The

power
valve

mechanism
so

called
vacuum

piston

type
utilizes

the

vacuum
below
the
throttle
valve

When
the

throttle
valve
is

slightly

opened
during
light
load

running

high

vacuum
is

created
in

the
intake
mani

fold
This

vacuum

pulls
the

vacuum

piston
upward

against
the

spring

leaving
the

power
valve
closed
When

the
vacuum
below
the
throttle

valve
is

lowered

during
full
load
or

accelerat

ing

running
the

spring

pushes
the

vacuum

piston
downward

opening
the

power
valve
to
furnish

fuel
Secondary
main

lIYlltem

pulled
out

through
the
main

nozzle

into
the
small
venturi

Due
to
the

double
venturi

of
the

secondary
system
the

higher

velocity

air

current

passing
through
the
main

nozzle

promotes
the
fuel
atomization

The
structure
is

almost
the

same
as

the

primary
side
The

secondary
main

system
is

a

Stromburg
type

Fuel
air
mixture

produced
by
the

functions
of
the
main

jet
main
air

bleed

and
emulsion
tube
in

the
same

manner
as
in

the

primary
system
is

11
1

I

1

1

Primary
vacuum

port

2

Secondary
vacuum

port

3

Diaphragm
chamber

cover

of

Diaphragm

spring

S

Diaphragm

6

Secondary
throttle

valve

7

Primary
theo
nle

valve
lWll
I

1
11

l
v
1

Vacuum

piston

2

Power

valve

ET02
a

EF
512

Fig
EF
27
Sectional

view

of

po
r

valve

Fig
EF
28
Full
throttle
al

high
peed

EF

16

Engine
Fuel

1

l
@
Vacuum
control
solenoid

valve

2
B
C
D

D

3

Coasting
jet

4

Secondary
slow

jet

5

ptug

6
Air
bleed

1

Secondary
slow
air
bleed

8
Secondary
main
air
bleed

9
Power
valve

10

Primary
main

air
bleed

11

Weight
and
outlet
valve

12

ptug

13

Primary
slow
jet

14

Ptirnar
slow
air

bleed

15

Accelerator

pump
assembly

16

AntkUeselingsolenoid
vain

17
Fast

idle
earn

18
Chok
e

connecting
rod

19
Fast
idle
earn
shaft

20
Ventuci

stopper
screw

21

Primary
and

secondary

small
venturi
Center

body
parts

Sets

Note
Do
not
remove
the

parts

marked
with
an
asterisk

It

EF726

Fig
EF
64

Removing
jets

Float

I
i

@
i

j

1

L

4
2
V
4

S

@

c
4
6

e4
11

Qll
1D

Yr

J
1

t
t

1

lil
c
@5
1

p
u

I

r

i
r

1
CJi

U

7
to1

8rtj
lv
Ji
JlJ

if
I
1

2

3

4

4

1

4

2

4

3

44

4
5

Hi

5
Secondary
main

jet

Primary
main

jet

Float
chamber

parts

Fuel
inlet

assembly

Lock
lever

Filter
set
screw

Fuel
f1Iter

Fuel

nipple

Needle
valve

body

Needle

valve

Diaphragm
chamber

aiSembly

EF227

Fig
EF

65
Removing
float

EF

32

Emission
Control

System

EARLY

FUEL

EVAPORATIVE

SYSTEM
E

F
E

DESCRIPTION
spring
and

counterweight
which
are

assembled
on
the

valve
shaft

projecting

to
the

rear
outside
of
the
exhaust

manifold
The

counterweight
is
se

cured
to
the
valve
shaft
with

key
bolt

and

snap
ring
EC
4
A

control
valve
welded
to

the

valve
shaft
is

wtalled
on
the

exhaust

manifold

through

bushing
This
con

trol

valve
is

called
Heat

control

valve
The
heat
control

valve
is

ac

luated

by
the

coil

spring
thermostat
Construction
of
the

early
fuel

evap

orative

system
is

shown
in

Figure

r
I

1

@

rW

9

Sc
w

10
Thennostat

spring

11

Coil
spriiig

12
Control
valve
shaft

13
Heat
control

valve

14

Bushing

15

Cap

16
Exhaust
manifold
1
Intake
manifold

2
Stove

gasket

ManifoktstOve

4
Heat
shield

plate

5

Snap
ring

6

Counterweight

7

Key

g

Stoppel
pin

EC532

Fig
EC
4
Early
Fuel

Evaporutive
tem
E
F
E

The

early
fuel

evaporative
system
is

provided
with
a
chamber
above

a

manifold
stove
moonted
between
the

intake
and
exhaust

manifolds

During

engine

warming
up
air
fuel
mixture
in

the

carburetor
is

heated
in
the
cham

bet

by
exhaust

gases
This
results
in

improved
evaporation
of

atomized
fuel

droplets
in
the
mixture
and
in

smaller

content
of

hydrocarbons
He
in
the

exhaust

gas
especially
in

cold
weather

operation

The
exhaust

gas
flow
from
the

engine
is

obstructed

by
the
heat
con

trol

valve
in
the

exhaust
manifold
and
is

changed
in

direction
as
shown

by

the
solid

lines
in

Figure
EC
4
The

exhaust

gas
heats
the
manifold
stove

Open
close

operation
of
the

heat

control
valve
is
controlled

by
the

counterweight
and
thermostat

spring

which
is
sensitive
to
the

ambient
tem

perature
around
the

exhaust
manifold
With
this
condition
the

heat
control

valve
is
in

the

fully
closed

position

obstructing
the
flow
of

exhaust

gas
As

engine
tempera
lure

goes
up
and

the

ambient

temperature
becomes

high

enough
to
actuate
the
thermostat

spring
the

counterweight
begins
to

rotate
clockwise
and

again
comes
into

con

tact
with

the

stopper
pin
With
this

condition
the

heat
control
valve
is
in

the
full

open
position
and
exhaust

gas

passes
through
the
exhaust
manifold
as

shown

by
the
dotted

lines
in

Figure

EC
4
without
heati

ng
the
manifold

stove
OPERATION

The

counterweight
rotates
counter

clockwise
and

stops
at

the

stopper
pin

mounted
on
the
exhaust

manifold

while

the

engine
temperature
is
low

EC
6

REMOVAL
AND
INSTAUATION
Emission
Control

System

EC533

Remove

snap
ring
D
and
lock
bolt

@
and
the

following
parts
can
be

detached
from
heat
control
valve

shaft

Key
00

Counterweight
@

TherI
lostat
spring
CID

Coil

spring

@

Note
As

previously
descnoed
heat

control
valv

1
is

welded
to
valve

shaft

@
at
exhaust
manifold
and

cannot
be

disassembled

To
install

reverse
the
removal

pro

cedure

INSPECTION

I
Run

engine
and

visually
check

counterweight
to

see
if
it

operates

properly

1
For
some
time
after

starling

engine
in
cold
weather

counterweight

turns
counterclockwise
until
it

comes

into
contact
with

stopper
pin
installed

to

exhaust
manifold

Counterweight
gradually
moves

down
clockwise
as

engine
warms

up

and

ambient

temperature
goes
higher

around
exhaust
manifold

2
When

engine
speed
is

increased

discharge

pressure
of
exhaust

gases

causes

counterweight
to

move
down

ward
clockwise

3

When
heat

con
trol
valve
is
in
the

full

open
position
coun

terweight

moves
further
clockwise
exceeding
the
1

Snap
ring

2

Lock
bolt

3

Key

4

Counterweight

5
Thermostat

spring

6
Coil
spring

7

Heat
control
valve

8
Valve
shaft

9
Stove
gasket

10
Manifold
stove

11
Heat
shield

plate

Fig
EC
5

Exploded
view
of
E
F
E
stem

position
described
in
1

1
above

and

stops
again
coming
into
con
tact
with

stopper
pin

j

EC246

1

Counterweight

2
S

topper
pin

3
Heat
control
valve

Fig
EC
6

Operation
of
counterweight

when

engine
is
cold

EC246

1

Counterweight

2

Stopper
pin

3
Heat
control

valve

Fig
EC
7

Operation
of
counterw
ight

when
ngine
is
hot

EC
7
2

With

engine
stopped
visually

check
E
F
E

system
for
the

following

items

1
Thermostat

spring
for
dismount

ing

2

Stopper
pin
for
bend
and
count

er

weight
stop

position
for

dislocation

3

Check
heat
control
valve
for

malfunction
due

to
break
of

key
that

locates
counterweight
to

valve
shaft

4
Check
axial
clearance
between

heat
control
valve
and
exhaust
mani

fold
Correct
clearance
is

0
7

to
1

5

mm
0
028
to
0
059
in

5
Check
welded

portion
of

heat

control
valve
and
valve
shaft
for

any

indication
of
crack
or

flaking

6
Rotate
heat
control
valve
shaft

by
a
finger
and
check
for

binding

between
shaft
and

bushing
in

closing

and

opening
operation
of
heat

control

valve
If

any
binding
is
felt
in

rotating

operation
move
valve

shaft
in
the

rotation
direction
several
times
If

this

operation
does

not
correct

binding

condition
it
is
due
to
seizure
between

shaft
and

bushing
and
exhaust
mani

fold
should
be

replaced
as
an
assem

bly

CHECKING
SPARK

TIMING
CONTROL

SYSTEM

DESCRIPTION

The

spark
tirnin
control

system

serves
to
control
the
distributor
vacu

um
advance
under

varying
travelling

conditions
so
as
to
reduce
HC
and

NOx
emissions

This

system
is
installed
on
non

California
automatic
transmission

models

SPARK
DELAY
VALVE

Automatic
transmission

models
only

This

valve
delays
vacuum

spark

advance

during
rapid
acceleration
it

also
cuts
off
the

vacuwn

spark
advance

immediately
upon
deceleration
The

valve
is

designed
for
one

way
opera

tion
and
consists
of
a
one

way
umbrel

la
valve
and
sinlered
steel
fluidic

restrictor