C3.3B Tier 4 Interim and EU Stage 3A Engines for Caterpillar Built Machines – Piston and Rings

Piston Ring Gap

1. Insert the piston ring into the lower part of the liner (the least worn part) with the piston.

Illustration 1	g03008660

2. Measure the ring gap with a feeler gauge.

   Table 1

   Top ring	New	C2.6 - 0.020 to 0.035 mm (0.00079 to 0.00138 inch) C3.3B - 0.25 to 0.40 mm (0.0099 to 0.015 inch)
   	Allowable limit	1.25 mm (0.0492 inch)

   Table 2

   Second ring	New	0.30 to 0.45 mm (0.012 to 0.017 inch)
   	Allowable limit	1.25 mm (0.0492 inch)

   Table 3

   Oil ring	New	0.25 to 0.45 mm (0.0099 to 0.017 inch)
   	Allowable limit	1.25 mm (0.0492 inch)

3. If the gap exceeds the allowable limit, replace the piston ring.

Clearance Between Piston Ring and Groove

1. Clean the rings and the ring grooves, and install each ring in its groove.

Illustration 2	g03008876

2. Measure the clearance between the ring and the groove with a feeler gauge or depth gauge.

   Table 4

   New	Top ring	0.050 to 0.090 mm (0.0020 to 0.0035 inch)
   	Second ring	0.090 to 0.12 mm (0.0036 to 0.0047 inch)
   	Oil ring	0.020 to 0.060 mm (0.00079 to 0.0023 inch)

   Table 5

   Allowable limit	Top ring	0.15 mm (0.0059 inch)
   	Second ring	0.20 mm (0.0079 inch)
   	Oil ring	0.15 mm (0.0059 inch)

3. If the clearance exceeds the allowable limit, replace the piston ring.

4. If the clearance still exceeds the allowable limit with new ring, replace the piston.

Piston Pin Bore

Illustration 3	g03008976

1. Measure the piston pin bore inside diameter in both the horizontal and vertical directions with a cylinder gauge.

   Table 6

   Piston pin bore inside diameter	New	C2.6 - 26.000 to 26.013 mm (1.02362 to 1.02413 inch) C3.3B - 28.000 to 28.013 mm (1.1024 to 1.1028 inch)
   	Allowable limit	C2.6 - 26.05 mm (1.02559 inch) C3.3B - 28.05 mm (1.104 inch)

2. If the measurement exceeds the allowable limit, replace the piston.

Oil Clearance Between Piston Pin and Small End Bushing

Illustration 4	g03009002

1. Measure the outside diameter of the piston pin where it contacts the bushing with an outside micrometer.

2. Measure the inside diameter of the piston pin bushing at the connecting rod small end with a cylinder gauge. Calculate the oil clearance.

   Table 7

   Piston pin outside diameter

   New

   C2.6 - 26.006 to 26.011 mm (1.02386 to 1.02405 inch) C3.3B - 28.006 to 28.011 mm (1.1026 to 1.1027 inch)

   Table 8

   Small end bushing inside diameter

   New

   C2.6 - 26.025 to 26.040 mm (1.02460 to 1.02519 inch) C3.3B - 28.031 to 28.046 mm (1.1036 to 1.1041 inch)

   Table 9

   Oil clearance between piston pin and small end bushing	New	C2.6 - 0.014 to 0.034 mm (0.00055 to 0.00134 inch) C3.3B - 0.020 to 0.040 mm (0.00079 to 0.0015 inch)
   	Allowable limit	0.15 mm (0.0059 inch)

3. If the clearance exceeds the allowable limit, replace the bushing. If it still exceeds the allowable limit, replace the piston pin.