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

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DESCRIPTION AND OPERATION (Continued)

PISTON AND CONNECTING ROD

The pistons are made of a high strength aluminum

alloy with an anodized top ring groove and crown.

Piston skirts are coated with a solid lubricant

(Molykote) to reduce friction and provide scuff resis-

tance. The connecting rods are made of ductile iron.

A pressed fit piston pin is used to attach the piston

and connecting rod.

Fig. 6 Piston and Connecting Rod Assembly

The camshaft is made of gray cast iron with twelve

machined lobes and four bearing journals. 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.

The rocker arms are made of stamped steel and

have a operational ratio of 1.6:1. When the push rods

are forced upward by the camshaft lobes the push

rod presses upward on the rocker arms, the rocker

arms pivot, forcing downward pressure on the valves

forcing the valves to move downward and off from

their seats (Fig. 8).

Fig. 7 Camshaft—Typical

1 – CAMSHAFT

3 – BEARING JOURNAL

Fig. 8 Rocker Arms 4.0L Engine

1 – CAPSCREWS

3 – PIVOT ASSEMBLY

4 – PUSH RODS

5 – ROCKER ARMS

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