Operator`s manual
OVERHAUL
MANUAL-
LYCOMING DIRECT
DRIVE AIRCRAFT
ENGINES
Section 2
General
Description
draulic
lifter
cylinder
outward.
This
action
forces
the
ball
check
valve
onto its
seat;
thus, the
body
of oil
trapped in
the pressure
chamber
acts as
a cushion.
During
the interval
when the
engine valve
is off
its
seat,
a predetermined
leakage
occurs
between
plunger
and cylinder
bore which
compensates
for any
expansion
or contraction
occurringin
the valve
train.
Immedia-
tely
after
the engine
valve
closes,
the amount
of
oil re-
quired to
fill the pressure
chamber
flows
in from the
supply chamber,
thereby
preparing
for another
cycle
of operation.
2-8.
CRANKCASE.
The
crankcase
assembly
consists
of
two reinforced
aluminum
alloy
castings
divided
at
the
centerline
of
the engine
and
fastened
together
by
a series
of
studs, bolts
and
nuts.
The mating
surfaces
of
the two
castings
are joined
without
the
use of
a gas-
ket, and
the
main bearing
bores
are
machined
for
the
use
of precision
type
main
bearing
inserts.
The
crank-
case
forms the
bearings
for the
camshaft.
2-9.
CRANKSHAFT.
The
crankshaft
is
made from
a
chrome
nickel molybdenum
steel
forging
and all
jour-
nal
surfaces
are
nitrided.
Earlier
models
were
pro-
videdwith
sludge
tubes
at each
crankpin.
These
sludge
tubes
are not
incorporated
in later
models.
This is
not
to imply
that
sludge
tubes
maybe
removed
and not
re-
placed
in
crankshafts
originally
manufactured
with
sludge
tubes.
These
tubes
must be
removed
and
re-
placed
at overhaul.
2-10.
CRANKSHAFT
COUNTERWEIGHTS.
A
system
of
dynamic
counterweights,
to
eliminate
torsional
vi-
bration,
is
provided
on
all six
and
eight
cylinder
and
some
four
cylinder
engines.
Consultthe
latest
edition
of
Service
Instruction
No.
1012
for proper
combination
and
location
on
the crankshaft.
2-11.
ACCESSORY
HOUSING.
The
accessory
housing
is machined
from
an aluminum
alloy casting
and
is
fastened
to
the rear
of
the
crankcase
and the
top
of
the
oil sump.
Accessories
are
mounted
on machined
pads located on
the rear of the
housing.
2-12.
CONNECTING
RODS.
The
connecting
rods
are
made
in the
form of
"H" sections
from
alloy steel
forgings.
They have
replaceable
bearing
inserts
in
the crankshaft
ends and
split type
bronze
bushings
in the
piston
ends.
The
bearing
caps
on the
crankshaft
end
of the
rods are
retained
by
two bolts
through
each
cap
secured
by
a crimp
nut.
2-13.
PISTONS.
The
pistons
are
machined
from
an
aluminum
alloy
forging.
The
piston
pin is
of the full
floating
type
with a
plug located
in
each end
of the
pin.
Consult
Service
Instruction
No.
1037 for
proper
piston
and ring
combinations.
2-14.
LUBRICATION
SYSTEM.
All
subject
engines,
with
the exception
of the
AIO series,
employ
a full
SPLASH
OIL TO ROCKER
ARMSVALVE
STEMS ETC
DRAIN OILTO SUMP
THRU OIL
DRAIN TUBES
ROCKER ARM
BUSHINGS GRAVITY OIL THRU SHROUD TUBES
USE OILTRANSFER
COVER
WHEN NOT USING
GOV.
GOV
PROP
G
O
V
.
OIL
GOVERNOR
IDLER
SHAFT
PUSH RODS
TAPPETS
TO SUMP
PUSH ROD SOCKETS
RETURN
LEFT
BANK
SPLASH
OIL
TO
DRAIN OILTO
UMP
CRANKCASE
OIL HEADER-LEFT
PISTONS,
PISTON
PINS,
SPLASH
OIL TO
PISTONSPISTON
PINS,CAMS,
ETC
CAMS, ETC.
CAMSHAFT
CRANKPIN
BEARING
NOS
CAMSHAFT
PRESSURE OIL
M
AIN
NO.4
MAIN
SPLASH
OILTO
BEARING
BEARING
BEARING
TACH.
DRIVE
MAIN
PUSH
ROD SOCKETS
CRANKCASE
HEADER-RIGHT
BEARING
N TAPPETS
HYD.PUMP
RIGHT BANK
AND DRIVE
SPLASH OIL
TO ROCKER
PUSH
RODS
AN FUEL PUMP
ARMS VALVE STEMS
ETC. ROKER ARM
AND DRIVE
- VACUUM PUMP
BUSHINGS AND DRIVE
DRAIN OILTO SUMP
THRU OIL DRAIN TUBES PRES. SCREEN
GRAVITYOILTHRU
OIL RELIEF
SHROUD
TUBES SPRIN
LOAD
VALVE
OIL COOLER
OIL PUMP BY-PASS VALVE DRAIN OIL TO SUMP
OPTIONAL
THERMOSTATIC
BY-PASS
VALVE
AVALABLE
SUCTION
SCREEN
OIL COOLER
OIL SUMP
Figure 2-4.
Lubrication
Diagram
- 6 Cylinder
Engines
Revised
January,
1970
2-3