C2.2 Engines for Caterpillar Built Machines Caterpillar

Markings on the Piston

Illustration 1	g03811576
Typical example

(1) The arrow that is on the top of the piston must face the front of the engine.

(2) The Shibaura name that is on the inside of the piston must align with the stamped number on the connecting rod.

Piston and Piston Rings

Illustration 2	g03811577
Typical example

Use a feeler gauge to measure the clearance between the piston ring groove and the piston ring. If the clearance is greater than the service limit, use a new piston ring and check the clearance.

If the clearance is within the service limit, renew the piston rings. If the clearance is outside of the service limit, renew the piston.

(1) Top piston ring

Shape of top ring (A) ... Half keystone

Gap of top piston ring ... 0.25 to 0.40 mm (0.00984 to 0.01575 inch)

Service limit for gap of top piston ring ... 1.0 mm (0.039 inch)

Note: It is difficult to measure the wear of the top piston ring. When either the intermediate ring or the oil control ring is outside the service limit, renew all of the rings.

Note: Install the letters "T" or "RN" toward the top of the piston. New top piston rings have a red identification mark. The identification mark must be on the left of the ring gap when the top piston ring is installed on an upright piston.

Note: New top piston rings have a yellow identification mark. The identification mark must be on the left of the ring gap when the top piston ring is installed on an upright piston.

Note: The top surface of the piston ring should be equally distant from the top face of the cylinder block at all points before the piston ring end gap is measured with a feeler gauge.

(2) Intermediate ring

Shape of intermediate ring (B) ... Taper

Clearance between piston ring groove and intermediate ring ... 0.04 to 0.08 mm (0.0016 to 0.0032 inch)

Service limit for clearance of intermediate ring ... 0.25 mm (0.0098 inch)

Gap of the intermediate ring ... 0.5 to 0.7 mm (0.020 to 0.023 inch)

Service limit for gap of intermediate ring ... 1.0 mm (0.039 inch)

Note: Install the word "Top" toward the top of the piston. New intermediate rings have a green identification mark. The identification mark must be on the left of the ring gap when the intermediate ring is installed on an upright piston.

Note: The top surface of the piston ring should be equally distant from the top face of the cylinder block at all points before the piston ring end gap is measured with a feeler gauge.

(3) Oil control ring

Clearance between piston ring groove and oil control ring ... 0.02 to 0.06 mm (0.0008 to 0.0024 inch)

Service limit for clearance of oil control ring ... 0.25 mm (0.0098 inch)

Gap of oil control ring ... 0.1 to 0.4 mm (0.00394 to 0.01575 inch)

Service limit for gap of oil control ring ... 1.2 mm (0.047 inch)

The oil control ring has two components. The two components of the oil control ring are installed in the following order.

1. Spring (D)

2. Oil control ring (C)

Note: A latch pin is used in order to hold both ends of the spring of the oil control ring in position. The ends of the spring of the oil control ring must be 180 degrees opposite the end gap of the oil control ring.

Note: The top surface of the piston ring should be equally distant from the top face of the cylinder block at all points before the piston ring end gap is measured with a feeler gauge.

(4) Piston

Diameter of the piston skirt ... 83.943 to 83.958 mm (3.3048 to 3.3054 inch)

Service limit ... 83.7 mm (3.295 inch)

Clearance of the piston skirt to the cylinder wall ... 0.0425 to 0.0615 mm (0.00167 to 0.00242 inch)

Service limit ... 0.25 mm (0.010 inch)

Diameter of the piston pin ... 27.994 to 28.000 mm (1.1021 to 1.1024 inch)

Service limit ... 27.97 mm (1.10118 inch)

Clearance between the hole for the piston pin and the piston pin ... −0.001 to +0.011 mm (−0.0004 to +0.0004 inch)

Service limit ... 0.02 mm (0.0008 inch)

Refer to Specifications, "Cylinder Head" for the piston height for a given gasket thickness.