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PART 8-2- 200, 250 C.I.D. SIX CYLINDER ENGINES
8-23
CYLINDER BLOCK
The cylinders are numbered from
1 to 6 starting at the front of the en-
gine. The firing order is 1-5-3-6-2-4.
The distributor, located on the left
front of the engine, drives the oil
pump through an intermediate drive
shaft.
The crankshaft is supported by
seven main bearings. Crankshaft and
thrust is controlled by the flanges of
the No. 5 main bearing.
The pistons have two compression
rings and one oil control ring. The
top compression ring is molybdenum
·
coated and the lower compression
ring is phosphate-coated. The oil
control ring assembly consists of a
serrated spring and two chrome-
plated steel rails.
VALVE TRAIN
The Six cylinder engines utilize
hydraulic valve lifters to provide
zero
lash.
The operation and parts
identification of the hydraulic valve
lifters are shown in (Fig.
4).
When
the valve
is
closed, the lifter assembly
is on the base circle of the camshaft
lobe and the valve push rod is in
its lowest
position.
With the lifter
assembly in this position, the plunger
spring expands, forcing the plunger
upward. This action is transmitted
to the
valve
rocker arm via the
valve push rod until there is solid
contact between the valve and the
valve end of the valve rocker arm
(zero valve lash).
As the lifter plunger moves up-
ward, the volume of the compression
chamber is increased, resulting in
reduced oil pressure in the compres-
sion chamber. Therefore, to equalize
the resulting pressure differential be-
tween the supply chamber and the
compression chamber, the disc valve
moves off its seat and permits oil to
flow from the supply chamber to the
compression
chamber.
When the
compression chamber becomes filled
with oil, the pressures in the two
chambers are
equalized.
The oil flow
ceases and the disc valve spring seats
the disc valve and closes the disc
valve port.
As the camshaft rotates, the lifter
assembly is raised by the camshaft
lobe.
This increases the push rod
force against the lifter plunger and
hydraulic pressure immedately builds
up in the compression chamber until
it acts
as
a solid member of the valve
operating mechanism
.
The lifter then
FIG. 2-Typical
Front
View
becomes a hydraulic ram which
forces the valve in the cylinder head
to open. During this period, a slight
leakage of oil past the plunger occurs
(calibrated leak down rate).
As the high point of the camshaft
lobe rotates and passes by the foot
of the valve
lifter,
the valve in the
cylinder head seats and the valve
lifter assembly is forced downward.
Reduced force on the lifter plunger
at
.
this time relieves the pressure on
the lifter plunger and it is free to be
moved upward by the plunger spring.
This action allows oil to flow once
again through the oil holes in the
lifter body and plunger.
The operating cycle is completed
for each revolution of the camshaft.
Zero clearance (lash) in the valve
train mechanism is maintained at all
times by the hydraulic force and ex-
pansion of the plunger spring be-
tween the lifter body and plunger.
LUBRICATION SYSTEM
Oil from the oil pan sump is
forced through the pressure-type lu-
brication system
(Fig.
6) by a rotor
pump.
A spring-loaded relief valve
in the pump limits the maximum
pressure of the system. Oil relieved
by the valve is directed back to the
intake side of the pump.
All the oil discharged by the
pump passes through a full flow-
type filter before it enters the en-
gine.
The filter has an internal by-
2S0-2v
pass valve and mounting gasket.
The by-pass valve permits oil to
by-pass the filter if it becomes
clogged,
thereby maintaining an
emergency supply of oil to the
engine at all times. An anti-drain
back diaphragm prevents a reverse
flow of oil when the engine is
stopped.
From the filter, the oil flows into
the main oil gallery. The oil gallery
supplies oil to all the camshaft and
main bearings through a drilled
passage in each main bearing web.
The timing chain and sprockets
are splash-lubricated from the oil
pan.
An oil slinger prevents leaka6e by
directing oil away from the crank-
shaft rear oil seal.
Cylinder walls, pistons and piston
pins are lubricated through a drilled
hole in each connecting rod which
indexes with a drilled hole in the
connecting rod journal of the crank-
shaft.
Oil from the main gallery feeds
pressure oil to the hydraulic valve
lifters and lubricates the lifter bores
in the cylinder block. A reservoir at
each valve lifter bore boss traps oil
so that oil is available for valve lifter
lubrication as soon as the engine
starts.
Oil under reduced pressure is fed
to the valve rocker arm shaft assem-
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