1977 DATSUN PICK-UP oil

Condition

ABNORMAL

COMBUSTION

backfue
afterflre

run
on
etc

Improper

ignition
timing

Fuel

system
out
of

order

Faulty
cylinder
head
etc

Others

EXCESSIVE
OIL

CONSUMPTION

Oilloak

Excessi
lo
oil

consumption

Others
Engine
Tune

up

probable
cause

Improper
ignition
timing

Improper
heat

range
of

spark
plugs

Damaged
carburetor

or
manifold

gasket

backfue
afterfire

Clol
l
ed
carburetor

jet

Improper
function
of

the
float

Uneven

idling
Run
on

Improperly
adjusted
B

C
D
D

set

pressure

Malfunction
of
anti

dieseling
solenoid
valve

Malfunction
of
auio
choke

Improperly
adjusted
valve
clearance

Excess
carbon
in

combustion
chamber

Damaged
valve

spring
backfire
afterflre

Malfunction
of

A
T
C

air
cleaner

Inoperative
ariti
backfue
valve

Loose
oil
drain

plug

Loose

or
damaged
oil

pan
gasket

Loose
or

damaged
chain
cover

gasket

Worn
oil
seal
in
front
and
rear
of
crankshaft

Loose
or

damaged
locker
cover

gasket

Improper
tightening
of
oil
filter

Loose
or

damaged
oil

pressure
switch

Cylinder
and

pioton
wear

Improper
location
of

piston
ring

gap
or

reversely
assembled

piston
ring

Damage
piston
rings

Worn

piston
ring
groove
and

ring

Fatigue
of
valve
oil
seal

lip

Worn
valve

stem

Inadequate
quality
of

engine
oil

Engine
overheat

ET32
Corrective
action

Adjust
ignition
timing

Use

specified
spark
plugs

Replace
them
with
new

parts

Disassemble
carburetor
and
check
it

Adjust
the
level
and
check
needle
valve

Adjust

Adjust

Check
or

replace

Adjust

Adjust

Remove
head
and

get
rid
of
carbon

Replace
it
with
a
new
one

Check
for
loose
vacuum
hoses

Replace
if

necessary

Replape

Tighten
it

Renew

gasket
or

tighten
it

Renew

gasket
or

tighten
it

Renew
oil
seal

Renew

gasket
or

tighten
it
but
not
too

much

Renew

gasket
and

tighten
it
with
the

proper

torque

Renew
oil

pressure
switch
or

tighten
it

Overhaul

cylinder
and
renew

piston

Remoun
t

piston
rings

Renew

rings

Repair
or
renew

piston
and

cylinder

Renew

piston
and

piston
ring

Replace
seal

lip
with
a

new
one

Renew
valve
or

guide

Use
the

designated
oil

Previously
mentioned

Condition

POOR
FUEL
ECONOMY

Se
the

xplanation

of
the
pow
r

dec

Oth
n

PROBLEM
IN

OTHER

FUNCTIONS

D
cr
d

oil

p
ssure

Excessive
wear
on
the

sliding

parts

Scuffing
of

sliding

parts

Floor

temperature
too

high
California

only
Engine
Tune

up

Probable
cause

Exceeding
idling
revolution

Inoperative
acceleration
recovery

Fuel

leakage

Malfunction
of
B

C
D
D

Malfunction
of
A
r
C
air

cleaner

Inadequate
oil

quality

Overheat

Worn

oil

pump
regulator
valve

Functional
deterioration
of
oil

pump

Blocked
oil
f1lter

Increased
clearance
in
various

sliding
parts

Blocked
oil
strainer

Inoperative
oil

gauge
pressure
switch

Oil

pressure
decreases

Improper

quality
or
contamination
of

oil

Damaged
air
cleaner

Overheat
or
overcoal

Improper
fuel
mixture

Decrease
of
oil

pressure

Insufficient
clearances

Overhea
t

Improper
fuel

mixture

Problem
in

fuel

system
Refer
to

Inspec

tion
of
Fuel

System

Problem
in

ignition
system
Refer
to
In

spection
of

Ignition
System

ET33
Corrective
action

Adjust
it

to
the

designated
rpm

Adjust
it

Repair
or

tighten
the
connection
of

fuel

pipes

Adjust

Check
and

replace

Use
the

designated
oil

Previously
mentioned

Disassemble
oil

pump
and

repair
or
renew
it

Repair
or

replace
it

with
a

new
one

Renew
it

Disassemble
and

replace
the
worn

parts
with

new
ones

Oeanit

Replace
it
with
a
new
one

Previousiy
mentioned

Exchange
the
oil
with

proper
one
and

change
element

Change
elemen
t

Previously
mentioned

Check
the
fuel

system

Previously
mentioned

Readjust
to
the

designated
clearances

Previously
mentioned

Check
the
fuel

system

Check
and

repair

Check
and

repair

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

Fig
EM

3

Crankshafl

PISTON

AND

CONNECTING
ROD

The

pistons
are

of
a

special
alumi

num

casting
and
have

struts
to
control

thermal

expansion
two

compression

rings
and

one
combined
oil

ring
The

piston
heads

are
slightly
dished

The

piston
pil1S
are
a

special
hollow

steel

shaft

They
are
full

floating
fit
to
the

piston
and

press
fit
to
the

connecting

rods

The

connecting
rods
are
of
a

special

forged
steel
Oil
is

sprayed
to
the

connecting
rod
small
ends

through

drilled

passages
in

the

large
ends
of

rod

Oil
holes
in

the

connecting
rods

are
located
so
as
to
insure

optimum

lubrication
under

heavy
load

0
50
1

o

E

Moao

Fig
EM
4

Piston
and

connecting
rod

CYLINDER
HEAD

The

cylinder
head
is

made
of
a

light
strong
aluminum

alloy
with

good

cooling
efficiency
it
contains

wedge

type
combustion
chambers
A

special

aluminum
bronze
valve
seat
is

used
on

the
intake
valve
while
a
heat
resistant

steel
valve
seat
is
installed

on
the

exhaust
valve
These

parts
are

all
hot

press
fitted

EM407

Fig
EM
S

Cylinder
head
Engine
Mechanical

CAMSHAFT

The
camshaft
is

made
of
a

special

cast
iron
and
is
loca
ted
inside
the

rocker
cover
Four
aluminum

alloy

brackets

support
it
Camshaft

bearings

are
lubricated
from
oil
holes
which

lead
to
the

main
oil

gallery
of
the

cylinder
head

Concentric

passages
are
drilled
in

the

front
and

rear

parts
of
the

earn

shaft

Oil
to
each
earn
lobe
is

supplied

through
an
oil

hole
drilled
in
the
base

circle
of
each
lobe
Lubricant
is

sup

plied
to
the
front
oil

gallery
from
the

2nd
camshaft

bearing
and
to
the

rear

oil

gallery
from
the

3rd
camshaft

bearing
These

holes
on
the
base

circle

of
the

lobe

supply
lubricant
to
the

earn

pad
surface
of
the
rocker
arm

and

to
the
valve

tip
end
The
cams
feature

a

long
overlap
profile
to
reduce
NOx

emission

Fig
EM
6

Camshafl

VALVE
MECHANISM

The
valve

system
has
the

pivot
type

rocker

arms
that

are
activated

directly

by
the
earn
mechanism

this
has
made

its

moving

parts
considerably
lighter

and

provides
ideal

high
speed
perform

ance

Dual

type
valve

springs
are
in

stalled

h

@l

if

Exhaust

Intake
EM084

Fig
EM
7
Valve
mechanism

EM

3
CAMSHAFT
DRIVE

The
camshaft
is
driven

by
a
double

row
roller
chain
driven

by
the

crank

shaft
The
tension
of
the

chain
is

controlled

by
a

chain
tcosioner

which

is

operated
by
spring
and
oil

pressure

The
rubber
shoe

type
tensioner

damps

vibration

of
the

chain
and
controls
its

tension

EM537

Fig
EM

8
Chain

driving

aystem

MANIFOLDS

The
intake
manifold
is
of
an
alumi

num
cast

alloy

The
exhaust
manifold
is

of
a
dual

design
and

incorporates
a
heat
control

valve
in
it
The

heal
control
valve
is

used
to

warm
the
intake
manifold

A

plate
is
installed
on
the
outer

face
of
the
manifold
to
draw
hot

intake
air

out

through
it
The
exhaust

pipe
is
connected
to
the

flanged
sur

face
of
the
exhaust
manifold

Fig
EM

9
Intak
and
exhaust

manifolds

r

I

I

PRELIMINARY
CLEANING
AND

INSPECTION

DISASSEMBL
Y

PRELIMINARY

CLEANING
AND

INSt

ECTION

Before

disassembling

engine
note

the

following

I
Fuel

oil
or
water

may
leak

past

cylinder
head
and
block
Prior
to

disassembling
check

cylinder
head

1
1ltermal
vacuum
valve

2
Check

valve

3
Altitude

compensator

in

air
cleaner

4
Air

gallery
pipe

S

Auto
choke

6
Automatic

temperature

control
air

cleaner

7
Anti
8ackfire
valve
A
B

valve

8
Boost
Controlled

Deceleration

Device
Bee
D
D

9
P
c
v

valve

to
Air
relief
valve

11
E

G
R

control
valve

12
B
C
D
D

control
valve
and

solenoid
valve

13

Emergency
air

relief
valve

14
Air

pump
air
cleaner

IS
Carbon
canister

16
Air
control

valve

11
Air

pump
Engine
Mechanical

ENGINE

DISASSEMBLY

CONTENTS

EM
4

EM
4
PISTONS
AND
CONNECTING
RODS

CYLINDER

HE
AD
EM
7

EM
7

front
chain

cover
oil

pan
and
oil

filter

gaskets
lInd
crankshaft
and
water

pump
seals
for

signs
of

leakage
past

their

gasketed
surfaces

2
Check
carburetor
and

fuel

pump

for
condition
fuel
hoses
for

deteriora

tion
cracks

or

leakage
of
fuel

past

their

jointed
or
connected

surfaces

Fig
EM

0
Emiuion
control
devic
s

California
mod
18
E
T366

3
Remove

carburetor
air

cleaner

Remove
fresh

air
duct

Disconnect
hot
air
duct
from

air

cleaner

Disconnect
air

cleaner
to
air

pump

hose
at
air

cleaner

Disconnect
air

cleanef
to
rocker

cover

hose
at
rocker
cover

Disconnect

air
cIeaner

to
air

con

trol

valve
hose
at
air

cleaner
Cali

fornia

models

only
Disconnect
air

cleaner
to
A

B
valve

hose
at
air

cleaner

Disconnect
air

cleaner
to

related

part
vacuum
hoses
at
air

cleaner

Loosen
air

cleaner
band
bolt
and

remove
carburetor
air

cleaner
as

sembly
from

carburetor

4

Plug
up
carburetor
air

horn

to

prevent
entry
of

foreign
matter

5

Remove

alternator
drive

belt

alternator
and

alternator
bracket

EM
4
6

Remove
air

pump
drive

belt
cool

er

compressor
and
idler

pulley
if

so

equipped

7
Remove
starter
motor
from
trans

mission

8

Visually

inspect
cylinder
head

cylinder
block
rocker
C
Ner

front

chain
cover
oil

pan
and
all
other
outer

parts
for
oil
water
and
fuel
leaks

breakage
or

missing
parts
such

as
bolts

and
nuts

9

Check

piping
and
electrical
cir

cuits
for
deterioration

breakage
fit

tings
discontinuity
or
insulation

DISASSEMBLY

To

remove

engine
from
vehicle

refer
to

the
instructions
under
the

Engine
Removal

and
Installation

ER
section

I

Remove
transmission
from

en

gine

2
Remove

clutch

assembly
from

flywheeL

3

Thoroughly
drain

engine
oil
and

coolan
t

by

removing
drain

plugs

Store

engine
oil
and

coolant
if

they

are

to
be

used

again

4
Place

engine
assembly
on

engine

stand

I

Remove

cooling
fan

2

Remove

right
engine

mounting

bracket

3

Remove
oil
filter
with
Oil

Filter

Wrench
STI9320000

4

Remove
oil

pressure
swi

tch

5

Install

engine
attachment
to

cylinder
block

utilizing
bolt

holes
in

alternator

bracket
and

water
drain

hole

6
Set

engine
on
stand

Engine
Attachment

ST05260001

Engine
Stand

ST050I

SOOO

EM410

Fig
EM
II

Engine
on

engine
land

Remove

oil
level

gauge

6
Remove

carburetor
from
intake

manifold

1
Disconnect
cylinder
block
to

P
C
V
valve
hose
at
P
C
V

valve

2

Disconnect
A
B
valve
to
E

G
R

passage
hose

at
E
G
R

passage

3
Disconnect
vacuum
tube
to

carburetor

hoses
white
and

yellow
at

vacuum
tube

4
Disconnect
fuel

hose
from

carburetor

5

Remove
dash

pot
bracket
from

intake
manifold

6
Remov
carburetor

attaching

bolts
and

remove
carburetor

assembly

and

gasket

7
Disconnect
distributor

high
ten

sion
cables
from

sparkplugs

8
Disconnect
vacuum
hose

from

distributor
and

remove
distributor
as

sembly

9

Disconnect
fuel

hose
from
fuel

pump
and

remove
fuel
and

vacuum

hoses
combined

from

cylinder
head

10
Remove
fuel

pump
assembly

from

cylinder
head

EM412

Fig
EM
12

Removing
fuel
pump

IJ
Remove
in
take
and
exhaust

manifold

assembly
from

cylinder
head

1
Disconnect
vacuum
hose

from

air
control
valve
and
remove
air
con

trol

valve
for
California
and
a
r
hoses

as
an
assembly
Engine
Mechanical

1
Air
control
valve

2
Distributor
EM531

Fig
EM
13

Removing
air
control

valve

Californio
model

2
Remove
carburetor
air
cleaner

bracket

3
Disconnect
vacuum
hose
from

E
G
R
valve

4
Remove
check
valve
from
air

gallery

pipe

5
Disconnect
E
G
R

tube
from

E

G
R

passage
and
exhaust
manifold

6
Remove
E

G
R

passage
and

E
G
R
valve

from
intake

manifold

I
E

G
R

passage

2
E
G
R
tube

Fig
EM
14
EM532

Removing
E

G
R

tube
and

passage

7
Remove
F
l

C
D

bracket
from

cylinder
head

if
so

equipped

8

Disconnect
vacuum
hoses
from

thermal

vacuum
valve

and
remove

thermostat

housing
and

gasket
from

cylinder
head

EM089

Fig
EM
15

Removing
thermostat

housing

EM
5
9
Remove

cylinder
block
to

P
C
V

valve
hose
blow

by
gas
hose

from

cylinder
block

10
Remove

manifold

attaching

bolts
and
remove
intake
and

exhaust

manifold

assembly
and

gasket
from

cylinder
head

Fig
EM
16

Removing
intake
and

exhaust

manifold
assembly

11
Remove
intake

and
exhaust

manifold

attaching
bolts
and

separate

intake

manifold
from

exhaust
mani

fold

12
Remove
air

gallery
pipes
from

exhaust

manifold

12
Remove

left

engi
e

mounting

bra
et

from

cylinder

blopk

13
Remove
air

pump
and
cooler

compressor
bracket

14
Remove

crankshaft

pulley
in

stalling
bolt
and

washer
and
then

remove

pulley
with
a
two

jaw
puller

15
Remove
water

pump
assembly

16
Remove
rocker

cover

17

R
emove

spark
plugs

18
Remove
fuel

pump
drive
earn

19

Remove
camshaft

sprocket

Refer
to
the

following
note

during

operation
when

removing
camshaft

sprocket
from

engine
installed
on
car

EM091

Fig
EM
17

Removing
cammaf

sprocket

r

28
Remove

cylinder
head

assembly

Use

Cylinder
Head
Bolt
Wrench

STl0120000
to

remove

cylinder
head

bolts
Loosen
bolts

from

CD
to

@
as

shown
in

Figure
EM
18

Fig
EM
IS

Cylinder
head
bolt

loosening
equence

Notes
When

removing
cylinder
heao

from

engiJJe
installed

on
car
follow

the

instructions
below

a
Turn
crankshaft

until
No
I

pilton

is
at
T
D
C

on
its

compression

stroke

b
Remove

rocker
Cover
and
fuel

pump

c
To
facilitate

assembling
o
tion

scribe
8
mark

on

timing
c
8in

and

camshaft

sprocket
with

paint
be

fore
removal

d
Loosen
camshaft
bolt

and
remove

fuel

pump
drive
earn

e

Support
timing
chain

by

utilizing

Chain

Stopper
STl7420001
bet

ween

timiilg
chains
as
shown
in

Figure
EM
19

This
0

peration
eliminates

the

prob

lem
of

realigning

timing
marks

on

timing
chain
and
crankshaft

sprocket

EM538

Fig
EM
19

Supporting
timing
chain

f

Remove
camshaft

sprocket

g
Loosen

cylinder
head
bolts

and

remove

cylinder
head
Engine
Mechanical

29
Invert

engine

30

Remove
oil

pan
and

oil
strainer

EM094

Fig
EM
20

Removing
oil
traintir

and
oil

pump

31

Remove
oil

pump
and
its
drive

spindle
See

Figure
EM
20

32
Remove
front
cover

33

Remove
chain
tensioner

and

chain
slack
side

guide

EM095

Fig
EM
21

Removing
chain
ten
ioner

and
tim

ing
chain

34
Remove

timing
chain

See

Figure
EM
2l

35
Remove

oil
thrower
crankshaft

wonn

gear
and

chain
drive

sprocket

Fig
EM
22

Removing
chain
drive

Proc
et

EM
6
36
Remove

piston
and

connecting

rod

a

mbly
Extract

connecting
rod

bearings
keeping
them
in
order

I

Fig
EM
23

Removing

pilton
and

connecting
rod
aat
m
b

y

37

Remove

flywheel
and

rear

plate

Be

careful
not

to

drop
them

EM415

Fig
EM

24

Removing
flywheel

38
Remove
main

bearing
caps

Use
Crankshaft

Main

Bearing

Cap

Puller
KVIOI04ISO

to
remove
center

and
rear

main

bearing

caps
Keep
them

in
order

KVIOI04IS0

EM539

Fig
EM
25

Removing
rear

main

bearing

cap

39

Remove
two
side
seals
from

rear

main

bearing
ca

p

40
Remove
rear
oil

seal

EM103

EM411

Fig
EM
29

Remouingpi
tonpin

Fig
EM
26
Remouing
rear
oil
eal

41
Remove
crankshaft

42
Remove
baffie

plate
and
cyl

inder
block
net

Fig
EM
27
Removing
baffle
plate
and

nel

PISTONS
AND

CONNECTING
RODS

Remove

piston
rings
with
a

ring

remover

O

EM102

Fig
EM
28

Removing
pilton
rings

2
Press

piston
pin
out
with
Piston

Pin
Press
Stand
STl3030001
Engine
Mechanical

3

Keep
disassembled

parts
in
order

CYLINDER

HEAD

I

Remove
valve
rocker

springs

Loosen
valve

rocker

pivot
lock
nut
and

remove
rocker
arm

by
pressing
valve

spring
down

Fig
EM
3D

Removing
rockerarrm

2

Remove
locate

plate
and
remove

camshaft

EM105

Fig
EM

31
Remouing
cammaft

EM
7
Note
Be

careful
not
to

damage
eam

shaft

bearings
and
earn
lobes

3
Remove

valves

using
Valve
Lifter

STl2070000

STl2070000

Fig
EM
32

Removing
ualves

Notes

a
Take

care
not
to
lose
valve

spring

seat
oil
seal
valve
collet

and
valve

rocker

guide

b
Be
sure

to
keep
camshaft

bearings

intact

or
the

bearing
center
is

liable

to
come
out
of

alignment

61

8

Exhaust
Intake
EM101

Fig
EM
33
Value
components