Jeep Cherokee

 Service Manual

Engine » 4.0L engine » Service procedures
Piston fitting

BORE GAGE METHOD

(1) To correctly select the proper size piston, a cylinder bore gauge, capable of reading in 0.003 mm (.0001 in.) INCREMENTS is required. If a bore gauge is not available, do not use an inside micrometer.

(2) Measure the inside diameter of the cylinder bore at a point 49.5 mm (1-15/16 inches) below top of bore. Start perpendicular (across or at 90 degrees) to the axis of the crankshaft at point A and then take an additional bore reading 90 degrees to that at point B (Fig. 20).

(3) The coated pistons will be serviced with the piston pin and connecting rod pre-assembled. The coated piston connecting rod assembly can be used to service previous built engines and MUST be replaced as complete sets. Tin coated pistons should not be used as replacements for coated pistons.

Fig. 18 Valve Spring Tester

1 - TORQUE WRENCH
2 - VALVE SPRING TESTER

(4) The coating material is applied to the piston after the final piston machining process. Measuring the outside diameter of a coated piston will not provide accurate results (Fig. 19). Therefore measuring the inside diameter of the cylinder bore with a dial Bore Gauge is MANDATORY. To correctly select the proper size piston, a cylinder bore gauge capable of reading in 0.003 mm (.0001 in.) increments is required.

(5) Piston installation into the cylinder bore requires slightly more pressure than that required for non-coated pistons. The bonded coating on the piston will give the appearance of a line-to-line fit with the cylinder bore.

Valve timing

Valve service

Piston fitting

Piston ring-fitting

Fitting connecting rod bearings

Fitting crankshaft main bearings

Form-in-place gaskets

Engine performance

Honing cylinder bores

Repair damaged or worn threads

Service engine assembly (short block)

Hydrostatic lock

Engine oil service