Piston And Connecting Rod; Camshaft; Rocker Arm; Valves - Jeep cherokee 2000 Service Manual

9 - 6 2.5L ENGINE
DESCRIPTION AND OPERATION (Continued)

PISTON AND CONNECTING ROD

DESCRIPTION
The pistons are made of a high strength aluminum
alloy, the piston skirts are coated with a solid lubri-
cant (Molykote) to reduce friction and provide scuff
resistance. The connecting rods are made of cast iron.
Fig. 6 Piston and Connecting Rod Assembly

CAMSHAFT

DESCRIPTION
The camshaft is made of cast iron with eight
machined lobes and four bearing journals.
Fig. 7 Camshaft—Typical
1 – CAMSHAFT
2 – LOBES
3 – BEARING JOURNAL
OPERATION
When the camshaft rotates, the lobes actuate the
tappets and push rods forcing upward on the rocker
arms which applies downward force on the valves.

ROCKER ARM

DESCRIPTION
The rocker arms are made of stamped steel and
have a operational ratio of 1.6:1.
Fig. 8 Rocker Arms—Typical
1 – CAPSCREWS
2 – BRIDGE
3 – PIVOT ASSEMBLY
4 – PUSH RODS
5 – ROCKER ARMS
OPERATION
When the push rods are forced upward by the cam-
shaft lobes the push rod presses upward on the
rocker arms, the rocker arms pivot, forcing down-
ward pressure on the valves forcing the valves to
move downward and off from their seats.

VALVES

DESCRIPTION
The valves are made of heat resistant steel and
have chrome plated stems to prevent scuffing. All
valves use three bead lock keepers to retain the valve
spring and promote valve rotation (Fig. 9).
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