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,·

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

520°F

Maximum

Spark

Plug

230°F

"

30

to

50

PSI

Maximum

10

to

20

PSI

Minimum

8

Quarts

Free Air

Temperature

Viscosity

Above

40°F

SAE

40

Below

40°F

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

0°F

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

40°F

SAE

40

Below 40°F

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 40°F or

above.

SAE 20 when free a ir tem

perature

is

below 40°F.

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