Mercury Monterey Specifications download pdf (Page 27)

1-20

GROUP

ENGINES

AND

EXHAUST SYSTEMS

VALVE TRAIN

The intake and exhaust valve as-

semblies are the rotating-type. The

tappets are the solid steel, mushroom-

type.

The camshaft is supported by

four bearings pressed into the block.

It is driven by a sprocket and timing

chain in mesh with a sprocket on the

crankshaft. Camshaft thrust is con-

trolled by a thrust plate located be-

tween the timing chain snubber pad

and the front journal of the camshaft.

An eccentric, made integral with the

camshaft, operates the fuel pump.

Silent lash rocker arms are used

which mechanically provide zero

valve lash and minimize valve train

noise and wear. The operation and

parts identification of the silent lash

rocker arms are shown in Fig. 4.

When the valve is closed, the

tappet is on the base circle of the

camshaft lobe and the valve push rod

is in its lowest position. With the

rocker arm in this position, the

eccentric actuating spring expands

forcing the plunger outward against

the valve and takes up any clearance

that may be present (Fig. 4).

As the camshaft rotates and the

valve begins to open, the valve push

rod is forced up against the rocker

arm which in turn pushes the

eccentric down on the valve. This

action moves the eccentric inward,

slightly and compresses the spring

and plunger (Fig. 4). As the high

point on the camshaft lobe rotates

ROCKER ARM

PLUNGER

VALVE OPENING

VALVE CLOSING

A1197-A

FIG.

4—Silent Lash Rocker Arm Operation

past the tappet, the push rod is

lowered and the valve spring closes

the valve. The eccentric actuating

spring expands and pushes the

plunger against the eccentric. The

eccentric then moves outward against

the valve to take up any clearance

that tends to be present.

The rocker arm eccentric func-

tions throughout the rocker arm

motion during the valve opening and

closing cycle, compensating for ex-

pansion or wear of the valve train.

Therefore, solid contact (zero lash)

between all parts of the valve train

mechanism is maintained.

LUBRICATION SYSTEM

Oil from the oil pan sump is

forced through the pressure-type

lubrication system (Fig. 5) by a

rotor-type oil 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.

The engine has a full-flow filter

which filters the entire output of the

pump before the oil enters the en-

gine.

The filter has an integral relief

valve and mounting gasket. The re-

lief 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 en-

gine 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 pas-

sage in each main bearing web.

The timing chain and sprockets

are lubricated through a flat on the

No.

1 camshaft bearing.

Oil slingers prevent leakage by di-

recting oil away from the crankshaft

front and rear oil seals.

Cylinder walls, pistons, and pis-

ton pins are lubricated through a

drilled hole in each connecting rod

which indexes with a drilled hole in

the connecting rod journal of the

crankshaft.

Oil under reduced pressure lubri-

cates the valve rocker arm shaft as-

sembly. The oil is fed through a

drilled passage in the cylinder block

at the No. 3 camshaft bearing. The

oil is metered by a groove in the

bearing. The passage in the block

indexes with a hole in the cylinder

head. An oil inlet tube directs the oil

into the hollow rocker shaft through

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Mercury Monterey Specifications Page 27

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