Franklin 6A4-150-B3, 6A4-165-B3, B31 Service Manual
SERVICE MANUAL
FRANKLIN AIRCRAFT
ENGINE
M
ODELS
6A4-150-85, 851, & 6A4-165-B5
4IRCOOLID
MOTOIS,
II~.
SYRACUSB.
HEW
YORI:
V.I.
A.
C
A.La
ADDRES.
AIRCOOLED
FRANKLIN
AIRCRAFT
ENGINES
Model
6A4-150-B5,ยท
B51,
&
6A4-165-B5
"NOT
LIABLE
FOR
ACCURACY
AND
EFFECTIVENESS
OF
ORIGINAL
TEXT."
Air Service Caravan
Co.,
Inc.
INSPECTION,
MAINTENANCE
AND
OVERHAUL
INSTRUCTIONS
C
LLEGt
F I
'0
J
ST.
I L
TECH
OLOG
AIRCOO
LED MOTOR
S, I
NC.
SYRACUSE
8,
NEW
YO
RK
TABLE
OF
CONTENTS
Se
cti
on
Page
S
ection
P
age
In
troduction
______
___
_______________
____ ____ ______
__ 5
XVII
Valves
and
Va lve Springs.......
___
.....
_____
25
Valves
__
... _
.......
__.
....
_......
_______
._._
... _..
25
II
Wa
rra n
ty
____
____________
_____
__.
________
____
._____
__ 5
Valve
Springs_
.... _.
____
._.
__
.. _
___
...
_____
... _
25
XVIII
Valve
Actuati
ng Mec
hanism.
____ .__
..__
__
26
III
Omit
7
Hydraulic Lifters
____ .__
..
__
..... _.. __..... ____
26
Hydraulic Lift
er
(Servicin
g)
..........._ 27
IV Repl
acement
Parts
and
Shipping
Lifter
Rods
and Tube
s_......
_. ____
..
_______
28
In
structions _______
_______
__
______
____ ____ ___ ___ 8
Rocker
Pins
a nd
Rockers
______
... _...
_.
__ . 28
V Eng i
ne
Specifications____
____
__ __ __
____
___
_____
9
XIX
Lubricating
System___
.. _...
__
._
.... _.. _.. _.
.....
29
Lubricating
Syste
m- I
nspection
and
Se
rvicing._.
___ .___
......
_._
.. _..
___ .__
29
VI
Table
of
Limits
and
Tolerances___ _____
__
10
Oil
Pan
_._..
___
____
..
___ .______
...
_.
__
._
......
____ . 30
Oil
Pump___. _
__
...
__
..
___
..... _
_____________
..
_.
__
30
VII
Re
comme
nded T
ightening
Torque
Oil
Inlet
Flo
at
(Flot o) _..
___
._.
__ .__ ._.
___
30
Valu
es _____
____
____
_________________ _____
_________
12
Oil By-
Pass
Plate
______________
__.
______ .._.
___
3 1
VIII
~Overhaul
Perio
ds
and
XX
Inlet
Manifold ______
.. . __. __
__
.. _____
___
.. _....
___
32
I
Perio
dic I ns
pec
tions
Check
List
______12-13
XXI
Accessory
Gear
Train
___
__ .__________
._.
____
.. _
33
IX
En
gin
e L
ubrication-GeneraL
__________
__
14
Magneto
Drive
Geor and Hub._.
_____
._
33
Magneto
Driven
Gear
___ .__ .._._
... _...
____
33
Generator
Driven Gear
___
.__.
__
.. _..
_.
____
33
X
Crankca se
______ ______
___
._
____ ___ _______
____
______ _ 14
Tachometer
Drive. __..
__
...
__ .___
..
____._.
___
33
Starter
Gear
Assemb
ly ... _...
____
..
___
..
___ . 34
X I
Cra nkshaft _____
______
____ ________________
_
_____ ___
15
C
rankshaft Bear
ings_____
______
_________
____
16
XXII
Ignition _____
___
__ .__
_______
... _____.__
___
...
_._ ..__
._
35
Cranks
ha
ft
Oil
Seal.-__
___
_________________
16
Magnetos-Pri
nci
ples
of Operation
35
1m
ulse
Starter
on the LA- 6
and
XII Ca
msha
ft
___
___________________._._
._________________
17
S6RN-21
Ma
gneto
s _
________._.
_._.
____
36
Magneto
Installati
on
.__
._
..
___
__
._________
39
Eisemann
Magnetos
-M
inor
X I
II
Timi
ng
Gear Case _
_______ .._______________
_______
17
Inspection .__
....
__
._
..
_.
___
__ .________
...
_.
37
Magn
eto T i
ming Check____ .___
.. _.
..
__..
___
38
XIV Connecting Rods_______________________
_..
______
__
18
Bend
ix-Sci nt i 110 Magneto_______
.. _
___
._.
38
Spa
rk
Plugs
__ ..______ .____
._
.. _...
__
.___
._.
______
38
XV Piston, Pis
ton Pins and Rings
___
____.______ 19
Pis
ton _______.____________
___
________
_________
___
___
19
XXIII
Carbureti
on .. _____..
_____________ ._____
.__
_________
40
Pis
ton
Pin _
__
______________________
_______________
19
Pist
on Rings
__ __ _____ .__
______
__.
_____
___
_____
__
20
XXIV
Generator
and
Volta
ge
Regulator._ ..____
42
Gen
erator
...._____
._
. __
_____ .___
...
_____ ._______
_ 4 2
Volt
age
Reg
ula
tor_____
..
_. ___
_______________ . 42
XVI Cy
linder
Assemb
ly ___
______
_________
.. __
__
______
2 1
Cylinders
__.
__ .________________._. ___.
__
...
__
....
21
XX
V
Starting Mo
tor
_._
.. _..
_.
____._. _______
...
____
.....
43
Va
lve
Guides
________
__.
______
__ .__
..... ___ .____
. 21
Valve
Seat Inserts_
___
____
________________ .._.
22
Studs
and
Fastenings.. ______.___
____ .._.
__
22
XXVI
Engine Assembly.
____ .___._____ .___ .____
......
__
44
Fins
__
.. .. _..
___
_.___
__
... _
._
...______.. . _
._. ___
... _
23
He
l icoi
Is
._
.. __._....
__
... . ____._.... .. _.
______..
__
23
XXVII
Engine Run
-In S
chedule
and
Testing
__
48
T
- I TRODUCTION
7 0
Years
of
Frankl in
engineering
experience
plus
the
highest
quality
in
ma terials a nd workm
ans
hip, t
o-
gether
with
the
most modern
manufacturing
methods
are
back
of eve
ry Fran
klin engine shipped from
our
factory.
It
is
the
purpose
of
this
manual
to furnish ready
reference
and
practical information on the operation,
inspection, preventive
maintenance
and
complete overhaul
of
the
model 6A4-1 50-83 a nd 831 and
6A4-165-B3
Franklin engines
and
their
accessories .
The
name
and
data
plate, which is located
either
on
the
starter
Bendix housing
or
on
the
lower right
hand
side of
the crankca
se just above
the
oil pan,
indicates
the
engine
model.
An
effort
has
been
mode
to
arrange
the
material
in
the
manual
so
that
the
description, function, in-
spection
and
repair
of
the
component
parts
of
the
engine
and
its accessories
are
completely covered
in
their
individual sections.
In referring to locations on
the
engine, it is
assumed
that
the
observ er's position
is
at
the accessory
end
of
the
engine, facing forward
in
line with
the
crankshaft.
Hence, t
he pro
peller end
will
be r
eferred
to
as
the
front
of
the
engine
irrespective
of
the
p03ition
the
engine
occupies
in the
air
craft. Cylinders
number
1, 3,
and 5 are
on
the
left side
of
the
engine
and
cyl
inders
numb
er
2, 4,
and 6 are
on
the
right
with
numbers 1 and 2 at
the
rear.
It
is
recommended
in
the
interest
of
safety,
operating economy
and
maximum
service life
of
the
engine
that
the
operating
limits, inspections, tolerances,
maintenance
and
overhaul
instruct
ions
and
methods
be strictly
adhered
to. It
is
also recommended
that
existing instructio ns
of
the
various
air
craft, pro-
peller
and
accessory
manufacturers
regarding
the
servicing
of
their
products
be
rigidly followed.
Additional or revised information will
be
issued
as
it
becomes available. Please keep us advised
of
your
current
mailing
address
to
insure
prompt
receipt
of
this
mat
erial.
To insure
that
your best
interests
be
served
and
satisfaction
be guaranteed,
we re
com
mend that
replacements
be
made
with
genuine
Franklin
parts
only. A list
of
authorized
Franklin d
istribut
ors,
together
with shipping instructions,
appears
on
page
7.
Please
address
all
technical
service inquiries
or
comments
to
Service Division, Aircooled Motors, Inc.,
Syracuse
8,
New York. They
wi
II
receive
prompt
and
courteous
atten
tion.
11-
WARRANTY
Aircooled Motors, Inc.,
warrants
each
new Franklin
engine
or
new
part
manufactured by
it
again
st
defects
in
material
or
workmanship
under
normal use,
but
its
obligation
under this war ranty
is
specif
i-
cally Iimited
to
replacing
or
repai ring
at
its factory
any
such
engine
or part which shall, within
90
days
after
delivery
thereof
to
the
original
purchaser
and
prior
to
50
hours of
operati
on, be
returned
to
Aircooled Motors, Inc., with its permission,
transportation
charges
prepaid, and which upon exa mi-
nation
by Aircooled Motors, Inc.,
is
determined
by Aircooled Motors, Inc. to be defective.
This
warranty
shall
not
apply
to
any
such
engine
or
parts
which have
bee
n repaired or
alt
ered outside
Aircooled Motors, Inc. factory
in
any
way so
as
to
affect,
in its
judgment
, its operation,
or
which h
ave
been
subjected
to
misuse, neglect, improper
maintenance
or
accident,
or
which sha
ll have been
oper-
ated
at
a speed
exceeding
the
factory
rated
speed.
Aircooled Motors, Inc.
makes
no
warranty
with
respect
to
ignition
apparat
us, carb
uretor
s, instrument
s,
tr
ade
accessories,
or
other
equipment
which it does
not
itself build
or manufact
ure inasmuch as such
eq
uipment
is
usually
guaranteed
by
the
respective
manufacturers
thereo
f.
The
foregOing
is
the
exclusive
warranty
made
by Aircooled Motors, Inco Ther
e a re no
other warranties
expressed or implied,
in
fact
or
in
law,
made
by Aircooled Motors, Inc.
AIRCOO
LED
MOTORS, INC.
Syracuse 8, New Yor k
5
....
c
e
....
...
.c
en
Ai
II -
PARTS
A D
SERVIC
E
IMPOR
T
A~T
Save
time
and shipping
expen
se
by ordering all parts from
the
Distributor in your territory. Send your order directly to him. Be sure
to
specify
model and serial number
of
engine for which parts are ordered.
AUTHORIZE
D
FRANK
LIN
DISTRIBUTORS
ALABAMA
Southern
Airways
527
Come
r Bldg., Birmin gha m
3,
Ala.
ALASKA
Pacific
Airmotive
Corporation
Sherril l Field,
Anchorage,
Alaska
ARKANSAS
Arkansas
Aviati on Service
Grider
Field,
Pine
Bluff,
Arkans
as
Central
Flyi
ng
Service
Municipal
Airp
ort,
Little
Rock,
Ark.
CALIFORNIA
Faulkner
Avia tion
Industries
Long
Beach
Municipal
Airport
L
ong
Beach
8,
Californ
ia
Hagel
in
Aircraft
Motors
Co.
933
Airway,
Glend
a le,
California
Rankin
Aviation Industries
Tulare, Califo
rnia
CANADA
Le
avens
Bros.
Air
Services,
Ltd
.
Barker
Airport
, To
ront
o,
Canada
Macleod
Airc
raft
Limited
55
15
Cypr
ess St.,
Vancouver,
B.
C.
Northwest
Industri
es,
Ltd.
Mupicipal Airport,
P. O. Box
517
, Edmonton,
Alb
erta
COLORADO
Moun
tain
States
Aviation
, Inc.
38
00
Dah
lia
Street,
Denver
16,
Colo.
CONNECTICU
T
Simsb ury Flying Service, Inc.
Simsbury
Airport, Si
msbury,
Conn.
DELAWARE
Aircrafters.
Inc.
Airport
, Rehobo
th
Beach,
Delaware
FLORIDA
Wallace Ai r
craft
Company
Sarasota,
Florida
Palm
Bea
ch
Aero
Corp.
L
antana, Florida
GEO RGIA
Aviation
Supply
Corporation
Atlanta
Municipal
Airport
Atla
nta
, Georgio
ILLINO
IS
Snyder
Ai
rcraft
Cor
porat
ion
53 15 W e
st
63 rd St., Ch
icago
38, III.
INDIA A
Air Sa les & Service, Inc.
Wier
Cook MuniCipal
Airport
In
dianapo
lis, In
diana
Munci
e A
viati
on
Corporation
MUncie
Airport, Munc
ie,
Indiana
Roscoe
Turn
er
Aero.
Corporation
Municipal
Airp
ort,
India
napolis, Ind.
Sky
Service
Corp
orati
on
Mun
icip
al
Airport,
Evansville, Ind.
IOWA
Hunter
Flying Service
P. O. Box 18 3, Ce
da
r R
apids.
Iowa
KANSAS
Harte
Flying Service
Municipal
Airport, Wichi
ta, K
ansas
KENTUCK
Y
Kentu
cky
Air
Transpor
t, Inc.
Bo
wman
Field, Louisville 5,
Kentucky
Louisville Fl
yin g Service
Bowman Field, Louisville 5,
Kentucky
MAINE
Airways, Inc.
Munici
pa l A irp
ort, Waterville,
Moine
Sky
Harbor
Flying Se rvice
A
ubu
rn-Lewist
on
Airport
Auburn, Maine
MARYLAND
Capitol
Airc
raft
Sa les
Hy
de
Field, Clinton,
Mar
yland
MASSACHUSETTS
Eastern
Aviation
, Inc.
Wenham,
Massachusetts
JenninQs
Bro .
Air Service
Grafton
Airport,
North
Graft
on,
Mass.
7
MICHIG
AN
Aircraft
Sales
Corporation
1040
Buhl Bldg.,
Detroit
26,
Mich.
Baker-Eberle
Aviation
Corp.
Detroit
City
Airport,
Detroit
5, Mich.
Barr
Aviation
Corp
.
Detroit
City
Airport,
Detroit,
Mich.
Michiqan
Central
Airlines, Inc.
Bishop Flying Service Division
Flint,
Michigan
Northern
Air
Service
Grand
Rapids
Airport
Grand
Rapids
8,
Michigan
MIN
NESO
TA
American
Aviation
Corporation
Flying Cloud Field, Hopkins,
Minn.
Hinc k Flying Service, Inc .
Metropolitan
Airport
Minneapolis,
Minnesota
Van
Dusen
Aircraft
Supplies
2004 Lyndale
Avenue,
South
Minneapolis
5,
Minnesota
MI
SSO
URI
Brayton
Flying Service, Inc.
Lambert-St.
Louis
Airport
St. Louis
21,
Missouri
Hampton
Aircraft,
Inc.
5852
Hampton
Avenue
St. Louis
9,
Missouri
Ong
Aircraft
Corporation
P. O. Box
214,
Kansas
City,
Mo.
Springfield
Flying Service, Inc.
Municipal
Airport,
Springfield, Mo.
Supply Division, Inc.
Lambert
Airport, Robertson, Mo.
N
EBRA
SKA
Omaha
Aircraft
Company
Municipal
Airport,
Omaha,
Neb.
N
EW
HAMPSHIRE
Wm.
E.
Martin
Flying Service
P. O. Box
276/
Concord, N. H.
NEW
JER
SEY
Safair
Flyi~g
School
Bendix
Airport,
Teterboro,
N. J.
NEW YORK
Buffalo A
eronautical
Corp.
Hangar
One, Buffa
lo
Airport
Buffalo, New York
Haven
Flying Service
Sche
nectady
County
Airpo
rt
Schenectady
, New York
Ithaca Flying Service, Inc.
Mun
icipa l Air
port,
Ithaca,
N.
Y.
Leech Airc r
aft,
Inc.
42
0 Lexington A
venue
Ne
w Yo rk 1
7, New York
O'Conn
or
Air
cra
ft Comp
any
Albany
Air
port, Albany, New Y
ork
NORTH CAROLINA
Piedm
ont
Aviation, Inc.
Sm
ith
-Reynolds Air
port
W
inston-Salem I,
Nor
th
Ca rolina
OHIO
Harrington
Air Service, Inc.
Mupici
pa l Airpo rt,
Mansfield,
Ohio
M
etc
alf Flyi
ng Service, Inc.
Toledo Munic ipal Airpor t, Toledo, O.
No rthw
ay
Flying Service
Norton Fie
ld, Colum bus, Ohio
Tri-St
at
e Avi
atio
n Corp.
Cincin
nati
Airport, Sharonv ille, O.
Tusca rawas Co
unty
Aviation, Inc.
Mu
nicipal Airport
New Phila
delph
ia, Ohio
OKLAHOMA
Fr
ank
Clarks
12
25
North
Robinson
Ok lahoma
City 3,
Oklaho
ma
OR
EGON
Westem Skyways Service
18
04
N. E. Union Avenue
Portl
and
12,
Oregon
A.
W. Whitaker
5001 -50
1 5 N.
E.
Uni
on Avenue
Port
land, Oreg
on
PENNSYLVANIA
Boulevard Airp
ort
, Inc.
G
etty
sburg, P
ennsy
lvania
G.
D.
Kelsey
Philadelph
ia
Municipal
Air
port
Philadelphia
42, Pennsy lvania
Krant z
Aeronau
tical C
orp
.
Part
Erie Airport, Erie, P
enn
.
Philadelp
hia
Aviation Corp.
1607
Finance
Building
Philadelph
ia
2,
Penn
sylvania
Scholter Aviati on
Compa
ny
Pitt
sburgh-Butler Airpor t, Butler, Po.
SOUTH
CAROLINA
Carolina
Aviat
ion, Inc.
Municipal
Airport
, Greenville,
S.
C.
Dixie
Aviation Comp
any
Municipa
l Airport, Col
umbia,
S.
C.
Hawth
orne Aero Supply
Hawthorne
Field,
Orange
burg, S. C.
SOUTH
DAKOTA
Dakota
Aviation Co.
W . W . Howes Muni cip
al
Airp
ort
Huron,
South
Dako
ta
TENNESSEE
Capitol Airways, Inc.
Howse Field, Nashvil le,
Te
nnessee
Southern
Air Services
Municipal
Airport, Memphis,
Tenn.
TEXAS
A
ircraft
Sales
Company
Meacham
Field, Fort
Worth,
Texas
Ca
nyon Aviation Service
Canyon,
Texas
Southwest Aircraft, Inc.
Mea
cham
Field, Fo
rt Wort
h, Te
xas
Weatherly-Campbell
Aircraft
Highland
Park
Airport, Dallas, Tex.
VIR
GI
NIA
Coastalair
Corporation
Virginia Beach Airport
Virginia Beach, Virginia
Virginia Airmotive
Woodr
um Field, Roanoke,
Va.
Virginia
Cub
Distributors
Shadwell, Virginia
WA
SH INGT
ON
Northwest
Aircraft
Distributing Co.
Box
649,
Vancouver,
Washington
Northwest
Air Service, Inc.
Boeing Field,
Seattle
8, W
ash.
WEST
VIRGINIA
Glenn T.
Clark
Clark Field, Winfield,
West
Virginia
WIS
CONSIN
Fliteways, Inc.
P.
O.
Box
1808, MilWaukee
1,
Wis.
Racine Flying Se"rvice
Horlick Racine Airport, Racine,
W
is.
IV
-
EPLACEMENT
PARTS
AND
SHIPPING
INSTRUCTIONS
When
con
tactin
g your a u
thorized
Franklin
distributor or
the facto
ry
concerning
par
ts or service,
ple
ase
give
both the
engine
model
and
the
engine serial
numbers
as stamped
on
the
data
plate
on
the
engine. This infor
mation
will
insure prompt,
accurate
service
and
pre
vent
undue
delay. Due to periodic
c
hanges in
engin
es,
the
engine
number
is
most important.
Wh
en
returning
par
ts
to your Franklin
distributor
or
the
factory, att
ach a tag
to
each
part
with your
n
ame, addr
ess a nd
the
model
and
serial
number
of
the engi
ne
from which
the
part
was rem oved,
togeth
er
with
the date
of your original
letter
of
refer
ence
to the p
art
in
que
stion. This
will
assure
the
prom
pt
handling
of your service requests.
When
shipping
parts
to the factory, be sure
they
are
shipped
pre
pa
id
and
that
they
are
carefully
packed
to prevent
damage.
Information regarding parts avail
able
in oversizes
or
und ersizes may be found
in
the
Parts
Book on
the 6A4-
1S0-B3
and
831
and
6A4-165-B3
engines.
Shou
ld
any
problem
arise
which
presents
the
need for specia l handling, or which requi res special
inform
atio
n, we
suggest
that
you
contact
the
neatest
Franklin
Authorized
Distributor or the
factor
y
and every
eff
ort
will
be
made
to
assist
you.
SPECIFY
MODEL
AND
SERIAL
NUM
BE R O F
ENG
I N E
8
fiG.
2.
Three
Quarter
Right Rear View
v- ENGINE SPECIFICATIONS
Model
Number
of
Cylinders
Bore
Stroke
Piston
Displacement
Compression Ratio
Rated
Speed in RPM
Rated
Brake
Horsepower
Idle Speed in RPM
Crankshaft
Rotation
Propeller
Shaft
Rotation
Propeller to
Crankshaft
Ratio
Maximum
Cylinder
Temperature
Maximum
Oil
Temperature
Oil Pressure
Oil Pressure
at
Idle
Oil
Capacity
Oil Specifications
Heavy Duty
Heavy Duty
Maximum
Operating
Time
between
Oil
Changes
Valve
Clearance
with
lifters
Bled
Down
and
Engine Cold
Firing
Order
Spark
Timing
Spark
Plugs
Spark
Plug
Gap
Fuel
Minimum
Octane
Fuel
Pump
Pressure (Bellanca Only)
Starter
Generator
Magneto
Breaker
Point
Gap
Maximum
Drop Single
Magneto
6A4-150-B3 6-B3
1
6
4.5"
3.5"
335 cu. in.
7:1
2600
150
HP
at
2600
RPM
500
to
600
Clockwise
Clockwise
1 : 1
520ยฐF
Maximum
Spark
Plug
230ยฐF
"
30
to
50
PSI
Maximum
10
to
20
PSI
Minimum
8
Quarts
Free Air
Temperature
Viscosity
Above
40ยฐF
SAE
40
Below
40ยฐF
SAE
20
25
Hours. More
often
if condi-
tions
warrant.
.040"
Cylinders 1
-4-5-2-3
-6
28
Deg rees BTC
Champion
J -
10
.014"
to
.018"
80
Nonleaded
Aviation
7
1
12
PSI
Maximum
12
Volt
15 Amp.
to
25
Amp.
.
019"
to
.021"
200
RPM
9
6A4-165-B3
6
4.5"
3.5"
335
cu. in.
7:1
2800
165 HP
at 2800
RPM
500 to 6
00
Clockwise
Clockwise
1 : 1
52
0ยฐF
Maximum
Spark
Plug
2
30
0
30
to
50 PS I Maxi"
mum
10
to
20
PSI
Minimum
8.8
Qua rts
Fr
ee
Air
Temperature
Viscosity
Above
40ยฐF
SAE
40
Below 40ยฐF
SAE
20
25
Hours. More
often
if
condi-
tions warrant.
.04
0"
Cy
li nder
s 1-4-5-2-3
-6
32 D
egre
es BTC
Cha
mp ion
J-
l 0
.0
14"
to
.018
"
80
Nonleaded Av
iation
7
1
12
P
SI
Maximum
12 Volt
25
Amp.
ot Spe cified
2
00
RPM
VI
- TABLE
OF
LIMITS
AND
TOLERANCES
Desc ripti
on
of
Limits
Cra
nkc
ase
& T
hr
us t
Wash
er
Dowel
Thrust
Was
her & Cr
ank
case
Dowel
Crankcase
Half
& Dowel
Crankshaft Bus
hing & Crankshaft
Crankshaft End
Clearan
ce
Co
nnecting
Rod Bushing &
Crankshaft
Connecting
Rod &
Bol
t (Diam.)
Co
nnecting
Rod Side
Clea
ran
ce
Crank
cas
e &
Mounting
Bra
ket
Dowel
Mounting
Bracket
& Cr
ankcase
Dowel
Camshaf
t Bushing &
Camshaft
Camshaft End Cl
eara
nce
Crankshaft
Gear & Crankshaft
Cam
sha
ft
Gear
& Ca
msha
ft
Cr
ankshaft
&
Camshaft
Gea
rs
(Backlash)
Cr
ankshaft & Magneto
Dr ive
Gear
Hub
Cranksh
aft Run
Out
Ma
in &
Crank
Journ
al
Fillet Radii
Cra nksh
aft
& Dowel
(Flange)
Piston
& Piston Pin
(Hand
Push Fit
with
Piston
at Room
Temperature
)
C
onnecting
Rod & Piston Pin
Piston Pin &
Plug
C
ylinder Liner
Exte
nsion Below
Cylinder
Flange
Cylinder
Barrel &
Piston
Pin (End
Clear
.)
Cylinder Barrel & Pi
ston
(Skirt)
Cylinde
r Barrel &
Piston (Top
land & lands
between
grooves)
Piston Ring
Gap
(All Rings)
Piston
& ,Top Piston Ring (Side
Clearance)
Piston &
2nd
Piston
Ring (Side
Clearance)
Pi
sto
n &
3rd
Piston
Ring (Side
Clearance)
Bushing &
Valve Rock
er Pin
Mfg.
Min.
.
0008T
.00lT
.
OOOST
.002l
.
008
.001Sl
.000Sl
.008
,OOOST
.OOOST
.001Sl
.006
.00lT
.OOOST
.004
.002T
.125
.0015T
.0000
.0007L
.000Sl
.
500
.015
.002l
.028L
.013
.00SSl
.0035l
,002l
.002l
10
Mfg
.
Max.
.0017T
.OOST
.001l
.
004l
.
020
.0034l
.
002l
.014
.001l
.
00ll
.002Sl
.010
.002T
.002T
.012
.0038T
.002
.140
.003T
.
0012
l
.002Sl
.51S
.033
.0035l
.
030l
.023
.007L
.005l
.
003Sl
.0035L
Max.
After Wea r
.004l
.010l
.001l
.0
06l
.026
.00
55L
.002l
.018l
.002l
.002l
.004l
.014l
.00lT
.OOO
ST
.016
.002T
.004
.00lT
.OO
OSl
.0
02l
.004l
.O
SO
.007L
.036l
.040
.009l
.007l
,005Sl
.007L
Va
lve Rock
er
Support (Stamped) & Val
ve Rocke
r Pin
Valve
Rocker
Support
(AI. Block) &
Valve
Rocker
Pin
Valve Rocker End
Clearance
V
alve
Guide & Cylinder
Head
(Early Engin
es)
V
alve
Guide & Cylind
er
Head
(la
te
Engines)
Valve
Guide & Intake
Valve
V
alve
Guide
& Exh
au
st Valv
e
C
ylinder
Head
& In
take
Valve
Seat Insert
Cyl
inder
Head & Ex
haust
Valve
Seat
Inse
rt
Val
ve
Lifter
& C
ran
kcase
Oi I
Pump Gea
r & Sh a
ft
Oi I
Pump
Drive Sh
aft
& Pum p Body
Oil
Pump Drive Gears & Shaft
Oil P
ump Sta t
ionary
Sha
ft
& P
ump Body
Oil Pu
mp
Driv
en
Gea
r &
Shaft
Oil Pu
mp
Gea
rs & Pu
mp Body
Oil Pu
mp Gears (Backlas
h)
Oil
Pump
Drive & Driven (
Back
lash)
Mag.
Drive G
ear Hub &
Gea
r
M
ag
. Drive Gea
r H
ub & Tach.
Dri
ve Gear
M
ag. Driv
e & Driv
en Gears
(Backlash)
Mag. &
Mag.
Adapt
er
Mag.
Driven
Gear
& Ma g
net
o, Driven
Gear
Hub
S
tarter Gear
Hub & Crankshaft
Tach. Drive & Drive n
Gear
s (Ba ckl
ash)
Ta
ch. Drive Connector & Ta
ch. Driven
Gear
Tach.
Connector
Sleeve &
Tach
. Drive
Connector
Tac
h.
Conn
ector
Sleeve & Tach. Drive H
ousing
Gen
erat
or Gear & Hu
b
G
enerat
or
Drive & Driven Gears
(Backla sh )
C
rankcase
& Dowel (Timing
Case)
Timing
Gear
Case & Crankcase
Dowel
T
iming
Gear Ca
se & Mag. Adapt
er
Tim
ing Gear
Case & Starter
Timing
Gear Case
& Ge
nerator
.001T
.001T
.003
.003T
.002T
.0
02Sl
.00
2Sl
.004T
.
00
4 1T
.001 l
.
OOOST
.00l
l
.
0000
.OOO
ST
.
000Sl
.002
l
.
004
.004
.002T
.OOOST
.006
.000Sl
.00
0Sl
.004T
.001
.001 2T
.
OOO
ST
.001Sl
.000
6l
.006
.0
00l
T
.000lT
.00
0Sl
.00
0Sl
.0
00Sl
.00lS
l
.
000Sl
.008
.004T
.003T
.
004
3L
.0043l
.00
6T
.006 1T
.00
2l
.002T
.
00
2Sl
.0
0l
ST
.001ST
.00
2l
.007l
.008
.008
.003ST
.
002
T
.010
.0045L
.
00
25l
.0052T
.003
.00
2T
.0
0l3T
.003Sl
.00
26l
.
010
.0013T
.0013T
.
004
Sl
.00
4Sl
.004SL
.0
02
SL
.001Sl
.00
8l
.0
02T
.
002
T
.
006
l
.
006l
.0
03T
.003T
.004l
.
OOO
ST
.004L
.
000
.
000
.0
04l
.010
l
.01
5
.01
2
.0
02
.0005T
.0 16
.0
04l
.003T
.
01
0l
.001T
.OOOST
.008l
.0
04l
.
016
.001 l
.001 L
.008l
.008l
.008l
11
VII-
RECOMMENDED TIGHTENING
TORQUE
VALUES
NAME
Stud
Stud
Stud
Stud
Screw
Screw
Screw
Nut
Nut
Nut
Standard
SIZE
OF
THREADS
Studs,
Screws
6'
1/4-20
5/
16-18
3/8-16
7/16-14
1/4-20
5/16-18
3/8-16
1/4-28
5/16-24
3/8-24
Nuts
TORQUE
VALUE
FOR
TIGHTENING <INCH-LIS.)
MINIMUM-MAXIMUM
25-60
50-90
75-110
95-195
60-75
105-
120
120-145
60-75
1
10-130
300-360
Special Applications
Oil Pump
Attaching
Screw
1/4-20
55-60
Crankcase
Cover Screw
5/16-18
Oil
Pan Holding Screw
5/16-18
60-75
Cylinder Hold-Down
Nut
3/8-24
240-300
Cylinder Hold-Down
Nut
7/
16-20
300-330
Crankcase
Tie Bold
Nut
5/
16-24
Camshaft
Bearing Stud
Nut
5/16-24
145-180
Mounting Bracket Stud
Nut
5/16-24
Distributing
Zone
to
Manifold Bolt
5/16-24
Starter
Mounting
Nut
3/
8-24
145-180
Spark
Plugs
14MM
180-240
Magneto
Nut
7/16-20
240-300
VIII-OVERHAUL
PERIODS
AND
PERIODIC
INSPE
TIONS
TOP OVERHAUL
MAJOR OVERHAUL
The
time
at
which a top overhaul
will
be neces-
No
definite
period
is
set
for a major overhaul.
sary
will
vary considerably with
the
type
of
opera-
Most engines
will
require
an
overhaul
after
600
to
tion
and
the
care
taken
of
the
engine
generally.
700
hours
of
operation.
The
periodic inspections
Proper i'1spections performed
at
the
specified
and
general
operating
characteristics
will
indica
te
periods (See inspection check list)
will
reveal
the
the
necessity
of
a major overhaul if one
is
needed
necessity
of
a top overhaul.
If
a top overhaul
is
not
sooner.
required
at
300
hours,
the
rubber
magneto
and
generator
drive shock absorber cushions should be
inspected
at
this time. Any worn cushions should
be
replaced.
12
----
------
-----------
----
------
-----
--
------
------
----
----
---
----
----
--------
------
--
----
--------------------
---
----
--
---------
--------------------------------
--
PERIOD C NSPECTIONS CHECK LIST
COVERING MODEL 6A4-150-B31, 6A4-150-13
and
6A4-165-83 ENGINES
Propeller
Blades
(Visual)
x
Ignition
Wires & Terminals
(Visual)
x
AccessibJe
Nuts
, Cop Screws & Fasteners fV;suaJ) x
Fuel
and
Oil Level
x x
x x
--------------
-
-------
--
-
Engine
Controls
(Free
Movement
& Full
Range)
x
x
x
x
--~-------------------
------------------------
--
Oil
Leaks
x
x
x
x
Fuel
Leaks
x x
x
x
Propeller
Bolts
(Check
for
Tightness & Safetying)
x
x
x
I~nition
Wires &Terminals
(Check
for
Tightne~-C~hafing&S~~~ere
d
ss,~ ~~~-
~~o~--
~----
------------
-------~
Connections-Clean)
x
x
x
Accessible
Nuts,
Cap
Screws & Fasteners
(Check
for
Tightness & Safetying)
x x
x
Engine
Controls
(Check
Free
MovemEmt, Full
Range & Linkage
System,
Lubricate)
x x x
Oil
Change
(More
Often
if
Operating
Conditions
Warrant)
x x x
------
--~------------
-----------------------
~--
---
Propeller
Track
x x
Exhaust
System
(Check
for
Leaks & Tightness)
x
x
x
Ora
in
Plugs & Fi
Ifer
Cops
(--=C:-=-h
-ckfo
n
--- --i -
&
sk
---
-------------
----------
-
e
----,
~-r---=T:-=ig=-:-h-t
-ess, ---;:;S~a-;;-fe
ty-,-ng
------;;;
-
--=G~a
----,
;--et
Condition)
x x
x
Cooling
Air
Baffles
(Check
for
Obstructions & Leaks)
x x x
Filters,
Strainers & Sumps
(Inspect & Clean)
x x
x
Compression
Check
(Check
all
cylinders
by
pulling
through
Propeller)
x
x x
--~
~~-~7-
--
_7~--~~~
--
--------------
--
--
--
--
Manifold
Equalizer
Pipe
Hose
Connection
(Check
condition
of
Hose
and
Tightness
of
Clamps)
x x x
Magneto
Breaker
P~o-in
ts----:
&
::-:-
---ibut-r
-----;-
(-=C
:-;:--ck
co-
nd---;-:-it
--=-
ion
of
rotor
&
-~
:;;--;::
Distr-----::-
--o-
he-
=-------
-
Distributor & Point
Condition & Gap)
x
x
Magneto
Timing & Synchroniza
_t_io_n
_________
~~~~
__
~~~~
__
~~
__
_________
________
_
Spark
Plugs
(Clean & Regap)
x
~
--------
-~
------~
----
--------~----~~
--
Cylinder
Fins
(Check
for
Breaks--Clean)
x
--
-
---
,
Carburetor
(Clean & Drain)
x
Fuel Lines
(Check
for
Chafing-Blow
Out
)
x
------
--~
--------
---~------
-
Engine
Mounts
(Chec
for
Tightness & Wear)
x
Generator
(Check
Connections,
Charging
Rate)
x
~---
~
~~
--
-----
---~----
~
--
Starter
(Check
Connections & Operation
of
Bendix
Drive)
x
Valve
Clearance
(Check & Adjust)
Every
200
Hours
Minimum
Magneto & Generator
Shock
Absorber
Drives
(Replace
worn
absorbers)
Every
300
Hours
Minimum
------
--------
-----~~--
---
----
~--
13
x
IX -ENG
INE LUBRICA ION
T
he primary
purpose
of
engine lubrica t ion is to
prevent met
a l-to-meta l conta ct between moving
par
ts. T
he
friction
accompany
ing
such meta
l-t
:>-
metal contact would
result in a loss
of
power, rapid
wear, a nd a
temp
erature
rise th
at might
cause part
s
to
fa
il. The a
ction
of the oil
is
to co
at
each met
a l
surface with a film. Be tween t
he
two films, other
l
ayers
of
the
oil sli
de
a long ov
er
each
other, t
hus
rep
lacing the high
frict
ion
of
metal-to-m
eta l c
on-
tact
by the low
inter
na l fricti
on
of
the
oil.
I n the process
of
circulating th
rough
the eng
ine,
oil absorb s he a t from
the
va rious
part
s. Most
of
this heat
is
dissipated
when the oil flows
through
the
oi
I coole
r.
It
is
ver
y im
port
ant that
an oil
of
the
proper
vis-
cosity
be used, since using too
heavy
an
oil will
impair
ci rcula ti
on
and insu
fficient
lubricati on w
ill
resu lt.
Operating
condition
s will control the period
be-
tween oil chang
es; however, t
he maxim
um
time
s
hould
not exce
ed
25
hou
rs.
Th
e S.A
.E.
lette
rs on a n oil co
ntainer do not
det
erm
ine the quali
ty of the lubric
ant.
The
refiner's
rep
utatio
n is y
our
best
guide
to the qua lity
of
the
product.
Pr
op
er lubrication
of y
our
engine should
be giv en
your most
ca reful a
ttention since improper
lubrica-
tion is evid
ence
d only after the dam
age
to
the
engi ne
has
occurred
and
is often very
cost ly. Using
the
proper
grade of
a good lu
bricant is cheaper
than
repa ir bills.
We
str
ong
ly
recommend
that
our
specifi
cation
a nd service
instructions
be strictly
followed.
ENGIN E
OI
L SPEC IFICA
TIONS
FOR MODEL
6
A4-150
-B3 A ND 831 AND
6A4-165-B3
ENG IN
ES
S
AE
40 when
free
air
temperature
is 40ยฐF or
above.
SAE 20 when free a ir tem
perature
is
below 40ยฐF.
x - CRANKCASE
The cra
nkcase is
built
in two h
alv
es of
high-
s
trength a luminum
alloy. (See Fig. 3. ) Each
crank-
ca
se half cont
ains
three
cylinder mounting p
ads
and
two e
ngin
e mount brack
et pads.
The left case
half
also
includes pads for the o
il
pump a nd oil
b
y-pass plat
e.
The
cran
kca
se whe n assembl
ed
as a unit
has a top
machined
face
to
take
a
cov
er
and a bottom machined
fac
e on which
the
o
il
pan
is
mounted. On
the model 6A4-
150-B3
a
nd
B31
eng
ines, a n oil seal is obtain
ed
between the
halves
at
the
nose
section
by two .135"-.14
5"
di-
ameter
synthetic
rubber packing
str
ips. Thes
e p
ack
-
ing
strips
fit
into grooves
mac
hin
ed into
the ma
ting
face
of
the
right
crankcase
half. The
se st rips
are
longer
than
the
grooves so
that they must
be
t
rimmed
to
length
after the
crank
case
is assembled
with
the
cra
nksh
aft
a nd camshaft. Ex
treme care
should
be taken
to
trim the ends
of t
he packing
strips absolutely flush w
ith
the face of
the
crank
-
ca
se.
This
is
partic
ula rly important
in t
he
nose oil
seal reces s, as
an
oil
leak
wil
l oc
cur
if t
he
packing
protrudes a t this loc
ation
. The model 6A4-
165-83
engine
does
not have
the rubber packing strips
be-
tween the c
ase
ha lves, and the packing st rip grooves
a re omit
te
d. An oil sea l
is obt
ained
on this
model
by
si
lk threads plac
ed
on the rig
ht
crankca
se half
in
the same positi
on
as the
grooves were located
in t
he othe
r models.
Fig.
46
shows t
he loc
ati
on of
these grooves. The threa ds a re
also trimmed flush
wi
th the
cra
nkcase fa
ces
oft
er
assembl
y. It is im-
po rtan t
that
the small rubber po cking rin
gs
at the
through
st
uds
be
in place b
efore
the
case
is re-
assembled. On
the
mod
el 6A4
-165-
B3
engin
e, it is
ne
cessa ry to put a sma
ll fiber was
her
under the oil
cro
ss-ov
er passage sea l rin g
to
pre
vent
it from fail-
ing in
to
the p
assa
ge. I t is advisable
to
ho ld the oil
sea
l p
ock
ing strips and rings in p
lace
with
a lig
ht
coot of
cup
grease
duri ng assembly.
7
6
3
FIG. 3.
I.
Main
Bearin
g J
ournal
2.
Propeller
Shaft
Bearing
Journal
3.
Nose Se
al
Adapting
Recess
4.
Engine
Mounting
Bracket
5.
Cylinder
Hold-Down
Stud
6.
Top
Crankcase
Cover
Mounting
Pad
10
Crankcase
7.
Rear
Through
Tie
Stud
8.
Crankcase
Assembly
Stud
9.
Top
Front
Through
Tie
Stud
10.
Front
Through
Tie
Stud
1 1.
Thrust
Washer
Mount-
ing
Pad
12.
Camshaft
Through
Tie
Stud
14
4
FIG.
4.
Crankshaft
and
Main
B arings
10
The
crankcase
on
the
model
6A4-165-B3
engine
has
drilled oil passages
and a mount
pad
to
take
a
propeller control valve'. This
pad
is
on
the
left front
of
the
crankcase
just
above
the
engine
mount
bracket.
The
two halves
are
joined internally
bya
series
of
six special
heat-treated
3/
8"
studs
located
at
the
main
bearing journals
and
four
heat-treated
5/ 16"
studs
located
at
the
camshaft bearing
jour-
nals.
Castle
nuts
safetied
with
cotter
pins
and
flat
washers
are
used on all internal
studs
. Two 3/
8"
studs
at
the
front
bearing
journal
and two
3/
8"
studs
at
the
rear
bearing
journal,
as well
as
one
5/
16"
stud
at
the
front
top protrude
through
the
right
crankcase
half. These five
studs
are
secured
externally using
flat
washers
and
elastic
stop
nuts.
Three
5/
16"-24x7-3/ 16"
hex
head
bolts
are
in-
stalled along the
top
of
the
case,
as
well as
three
5/
16"-24
x 1-3/
8"
hex
head
bolts installed
at
the
front
end
of
the
engine
straight
through
both
crankcase
halves. Plain 5/ 16" washers
are
used
under bolt
heads
and
under
the
specified
elastic
stop
nuts.
When
assembling
the
crankcase
halves, observe
that
the
aligning dowels
fit
in their respective holes
and
draw
up
the
crankcase
assembly
nuts
evenly.
XI-CRA
1
5
Wh
en
assembled with mati ng halves,
the
crank
-
sh
aft main bearing
hole
is
bored to 2,406" to
2.407"
and the
camsha
ft beari ng hole is bored to
1. 1245"
to 1
.1250
".
Each
of
the
six cylinder pods are s
tudded
at the
proper locations
as
follows: Four studs, 7/ 16-
14
NC
stud
end, 7/ 16-20-NF-
3 nut
end, dr
iven to a h
eight
above
pad
of 1
-1
/ 8". Four studs 3/ 8-1 6 NC
stud
end, 3/
8-24
-NF-3 n
ut
end, driven to a height
above
pad
of 1-1/
16".
One
pad
is loc
ated
at
each of
the
four low
er
out-
side corn e
rs
of
the
cra nkc
ase
to
acc
omm
odate
the
engine
moun ting brackets. Four dowels
are
located
in
the
case
to align
the
brackets, one do
wel
for each
bra
cket. On
the
early engines, the
brackets
a re
secured to
the case by
mea
ns
of two
studs.
5/
16-18 x 7/
8" hex
hea
d cap screws are used on
the
later
engine . Some engi
ne
models u
se
flat
washers
and
drilled he
ad
hex
ca p scre
ws
safetied
with lacing wire. On some engines
the low
er righ
t-
hand
bracket
is
of
special desi
gn with a p
ad
for
fuel
pump attachm
ent.
When
the
crankcase
is
disasse mbled a t engi
ne
overhaul, it
is
important
that
all plugs be removed
and
the
oil galleries and o
il
pass
ages
be thorough ly
flushed
out
before reinstalling
the plugs.
KSHAFT
1. Cr
ankshaft Gear
2.
Center Main
Journal
3.
Connecting Rod Journal
4.
Front
Main
and
Pro-
peller
Shaft Journa
ls
5.
Re
ar Main
Journa
l
6 .
Re
a r Main Bearing
7.
Cente
r M
ain Bearing
8. Fro
nt Main Bearing
9. Propeller Sha ft Bearing
10.
Pr
ope ller Bolt Flan
ge
Bush ing
15
The
crankshaft
is a one
piece, six throw, alloy
steel forging,
heat
treated
and
designed
to
with-
stand
high stress.
It
is
drilled f
or lightness
and
to
supply lubrication to all
the
beari ngs. (See Fig. 4. )
The
fillets
ground
on
the
crankshaft
have a
.125"
to
.140"
radius on
the
main
bea ring journals
and
connecting rod bearing journals.
These
fillets reduce
the
tendency
toward localization of stress
and
for
this reason it
is
important
that fil
let
specifica -
tions be observed
if
the
crankshaft
is
reground.
Also,
after
regrinding
the
journals, the fillets should
be
shot
peened
according
to
Aircooled Motors speci-
fication # 1 1981 .
CRANKSHAFT BEARINGS
The
crankshaft
is
supported
in
the
crankcase
by
five
split
steel-backed,
main
bearings
of
.0770"
to
.0775"
wall thickness
after
plating
. (See Figure
4.)
The
bearing shells
have
0 crush fit to secure
them
in
the
crankcase
bore
and
insure rigid
support
for
the
crankshaft.
The
five bearings
are
referred to by
number
with
the
# 1 bearing
at
the
rear
of
the
engine.
It
is
essential
that
the
bear
ing shell halves
containing
the
oil holes be
assembled
so
that
they
motch
the
oil
passages
in
the
left
crankcase
half.
Figure
No.4
shows
the
#4
main
bearing
with a
single oil groove. This
bearing
on
the
model
6A4-165-B3
engine
has
an
additional
oil
transfer
groove
to
provide a
passage
for propeller control
oil. This bearing having
the
oil
transfer
groove
will
. be suppl ied for service
replacement
for
the
#4
and
#5
bearings
on
all model engines referred to in
this
manual.
The
crankshaft
end-play, when
the
crankshaft
is
fitted
in
the
crankcase,
is
.008"
to
.020"
and
is
controlled by two split
bronze
thrust
washers lo-
cated
and
doweled to
the
front
and
rear
sides of
the
crankcase
web
of
the
front
center
main
bearing
support
in
both
crankcase
halves.
The
end
play
should be
checked
with
both
crankcase
halves
sepa-
rately
as
well
as
after
assembly
to
make
sure
that
the
.008"
minimum
clearance
is
obtainable.
Thrust
washers
must
be replaced in pairs
as
slight
varia-
tions in thickness exist between
different
pairs.
The
crankshaft
main
bearing journal
diameter
is
ground
to
2.249"
to
2.250"
and
the
connecting
rod
bearing journal
is
ground to
1.9365"
to
1.9375".
When
assembled in
the
crankcase,
the
clearance
between
the
crankshaft
journa
ls
and
main
bearings
is
.002"
to
.004".
Eight bushings with inside
diameter
threaded
3/8"
-24
NF-3
are
pressed into
the
flange
at
the
front
of
the
crankshaf
t for
attaching
the
propeller.
The
.6265"
to .627
0"
major
outside
diameter
of
the
bushing
is
a .
0015"
to
.003"
press fit
in
the
.624"
to
.625"
reamed holes in
the crankshaft
flange.
The
model 6A4-150-B31
has a 5"
diameter
bolt circle
flange.
The
model
6A4-150-B3
and
6A4-165-B3
engines
hqve a
standard
SAE-3 5.25" bolt circle
flange. Two
Woodruff
key
seats
3/
16
by 1-1/
8"
are
cut
in
the
rear
main
bearing journal extension
for
att
aching
the
crankshaft
gear, starter
gear
and
accessory drive gear.
The
crankshaft
runout,
token
with
the
shaft
sup-
ported on its main
bearing
journals, should
not
exceed
.002"
total
indicator reading.
The
crankshaft
of
the
6A4-165-B3
engine
is
drilled
at
the
front
main
journal to provide a pas-
sage
for propeller
actuating
oil from
the
crankcase
to
the
hollow propeller
shaft.
The
aluminum
plug
closing
the
end
of
the
propeller
shaft
should
not
be
removed
except
possibly
at a major
overhaul when
it
is
desired
to
thoroughly
clean
the
shaft.
This plug
is
assembled with a press
fit
in
the
shaft
and
is
safetied
with a
set
screw. If
the
plug
is
ever re-
moved, it should be replaced by a new
part,
as
the
old one
is
usually
damaged
by removal.
The
1/8"
pipe plug, which
is
installed in
the
center
of
the
aluminum
plug, should also never be removed ex-
cept
when a hydraulically
actuated
propeller is
installed
on
the
engine.
The
hollow propeller
shaft
carries
engine
oil which
will
escape
if
either
plug
is
not
in
place
during
engine
operation.
The
crankshaft
flange
has
the
following
mark-
ings on
the
rim
of
its outside
diameter:
"No.
1
U.D.C.,
24
and
28
degrees."
The
No. 1 U.D.C.
mark,
when in line with
the
center
line of
the
crank-
case
at
the
top
of
the
engine, refers to top
dead
center
of
No. 1 cylinder.
The
28
degree
mark
is
used for ignition timing on
the
model 6A4-1 50-B3
and
B31
engines
and,
when
01
igned with
the
crank-
case
center
line,
refresents
28
degrees before top
dead
center
on No. cyl
inder
when
on
the
compres-
sion stroke.
The
32
degree
mark
is
used for igni-
tion timing
the
6A4-165-B3
and,
when al igned
with
the
crankcase
center
line, represents
32
de-
grees before
top
dead
center
on
No.1
cylinder when
on
the
compression stroke.
Before installation
at
the
factory, every
crank-
shaft
is
100% magnetically
inspected
and
tested
for dynamic
and
static
balance.
CRANKSHAFT OIL
SEAL
!
4
FIG.
5.
Crankshaft
Oil Seal
1.
Crankshaft
Oil
Seal
3.
Oil
Seal
RetainerWasher
Spring
4.
Retainer
Washer
2.
Crankshaft
Oil
Seal
Attachment
Screw
Packing
A spring loaded all seal
is
installed
in
the
3.248"
to
3.250"
recess in
the
front end
of
the
crankcase,
formed by
the
assembly of
the
two
crankcase
halves. (See Fig. 5. )
The
free length
of
the
spring
itself
in
the
open position should
measure 7 -1 / 8"
to
7-1 / 4".
Be
sure
to
specify
the
correct
part
number
when ordering
the
seal. (See Fig. 5-1.)
The
spring
side of
the
seal
is
towards
the
rear
of
the
engine
and
a light
coating
of
sealing compound
is
applied
to
the
outside
surface
of
the
seal before pressing
the
seal into place.
The
split
in
the
seal should be
located
approximately
45
degrees
from
the
crank-
case
parting
line
to
insure
that
no oil
seepage
will
occur where
the
seal ends come together.
The
seal
should be
topped
into position evenly to
prevent
distortion
and
insure proper
seating
in
the
crank-
case
bore. A
split
retainer
plate
is
used
to
hold
the
seal in position. This
plate
is
attached
to
the
front
end
of
the
crankcase
by
means
of
two
1 /
4"
-20
x 1/
2"
hex
head
cap
screws
and
two 1 /
4"
shakeproof
washers.
16
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