C3.3 Industrial Engine Caterpillar

Illustration 1	g00888215
A typical example of a piston and rings

(1) Top compression ring

Naturally Aspirated

The shape of the top compression ring ... Rectangular with a barrel face

Width of the top compression ring ... 2.475 to 2.49 mm (0.097 to 0.098 inch)

Clearance between the top compression ring and the piston groove ... 0.09 to .15 mm (0.0035 to 0.0059 inch)

Ring gap ... 0.30 to 0.55 mm (0.0118 to 0.0216 inch)

Turbocharged

The shape of the top compression ring ... Keystone with a barrel face

Width of the top compression ring ... tapered

Ring gap ... 0.30 to 0.55 mm (0.0118 to 0.0216 inch)

Note: When you install a new top compression ring, make sure that the word "TOP" is facing the top of the piston. New top piston rings have a red identification mark which must be on the left of the ring end gap when the top piston ring is installed on an upright piston.

(2) Intermediate compression ring

The shape of the intermediate compression ring ... Internal step in the bottom edge with a tapered face

Width of intermediate compression ring ... 2.47 to 2.49 mm (0.097 to 0.098 inch)

Clearance between the intermediate compression ring and the piston groove ... 0.05 to 0.09 mm (0.002 to 0.003 inch)

Ring gap ... 0.70 to 0.95 mm (0.0275 to 0.0374 inch)

Note: When you install a new intermediate compression ring, make sure that the word "TOP" is facing the top of the piston. New intermediate rings have a green identification mark which must be on the left of the ring end gap when the top piston ring is installed on an upright piston.

(3) Oil control ring

Shape of oil control ring ... Two-piece coil that is spring loaded

Width of oil control ring ... 3.47 to 3.49 mm (0.1366 to 0.1374 inch)

Clearance between the oil control ring and the groove in the piston ... 0.03 to 0.07 mm (0.0011 to 0.0027 inch)

Ring gap ... 0.30 to 0.55 mm (0.0118 to 0.0216 inch)

Note: A 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 installed opposite the end gap of the oil control ring.

Note: Ensure that the ring end gaps of the piston rings are spaced 120 degrees from each other.

Piston

Note: An arrow which is marked on the piston crown must be toward the front of the engine.

The combustion bowl re-entrant angle for the turbocharged engine ... 80 degrees

The combustion bowl re-entrant angle for the naturally aspirated engine ... 70 degrees

Piston height above cylinder block ... 0.21 to 0.35 mm (0.008 to 0.014 inch)

Width of top groove in piston for the naturally aspirated engine ... 2.58 to 2.60 mm (0.1016 to 0.1024 inch)

Width of top groove in piston for the turbocharged engine ... Tapered

Width of second groove in piston ... 2.54 to 2.56 mm (0.1000 to 0.1008 inch)

Width of third groove in piston ... 3.52 to 3.54 mm (0.1386 to 0.1394 inch)

Piston pin

Diameter of a new piston pin ... 39.694 to 39.700 mm (1.5628 to 1.5630 inch)

Diameter of the bore for the piston pin ... 39.703 to 39.709 mm (1.5631 to 1.5633 inch)