Piston Measurements and Replacement

Fig. 14 Measuring Piston Diameter:

PISTONS

When measuring piston diameter, place micrometer 3/16 inch below cross slot or 3/8 inch below oil ring groove, Fig. 14. Cylinder liner diameter is measured two inches down from top of liner and perpendicular to the cylinder centerline. The difference between the two readings should be .0010-.0018 inch on 4.5L engines or .0004-.0020 inch on 4.9L engines. Cylinder bore out of round should not exceed .0008 inch. If any reading is not within specifications, the piston and cylinder liner must be replaced. No attempt should be made to rebore or hone the cylinder liner. Refer to CYLINDER LINER procedure.

PISTON PINS

Piston pins are a matched fit with the piston and are not available for separate replacement. Piston pins are pressed into the connecting rods and will not become loose enough to cause a knock or tapping until after very high mileage.

PISTON RINGS

On these engines, replacement rings are available in standard size only. If piston ring clearance is excessive, the piston and cylinder liner must be replaced. Refer to CYLINDER LINER procedure.