3126B Marine Engine Caterpillar

Two-Piece Articulated Piston

Illustration 1	g01388740

Illustration 2	g01388762

(1) Crown assembly

(2) Connecting rod

Note: Install the connecting rod and piston group in the engine with the part number to the rear of the engine. The rear of the engine is the flywheel end of the engine. Lubricate the piston group with clean engine oil before the piston group is inserted into the block.

Top Ring and Intermediate Ring

(3) The top ring has the mark "UP-1".

Install the piston ring with the side marked "UP-1" toward the top of the piston. The yellow stripe faces to the right of the ring end gap.

The ends of the piston ring have a clearance when the piston ring is installed in a cylinder with a specific bore size.

Gauge diameter ... 110 mm (4.3 inch)

Clearance ... 0.40 ± 0.10 mm (0.016 ± 0.004 inch)

(4) The intermediate ring has the mark "UP-2".

Install the piston ring with the side marked "UP-2" toward the top of the piston. The red stripe faces to the right of the piston ring end gap.

Thickness of the new piston ring ... 2.98 ± 0.01 mm (0.1173 ± 0.0004 inch)

The ends of the oil control piston ring have a clearance when the ring is installed in a gauge with a specific diameter.

Gauge diameter ... 110 mm (4.3 inch)

Clearance ... 0.60 ± 0.10 mm (0.024 ± 0.004 inch)

Oil Control Ring

(5) The oil control piston ring has a spring that is installed with the ring. The gap in the spring should be a distance of 180 degrees from the ring end gap when the oil control piston ring is assembled. The light green colored portion of the spring must be visible at the ring end gap.

Width of the groove in a new piston for the oil control piston ring ... 4.041 ± 0.013 mm (0.1591 ± 0.0005 inch)

Thickness of the new piston ring ... 3.985 ± 0.010 mm (0.1569 ± 0.0004 inch)

The ends of the oil control piston ring have a clearance when the ring is installed in a gauge with a specific diameter.

Gauge diameter ... 110 mm (4.3 inch)

Clearance ... 0.45 ± 0.15 mm (0.018 ± 0.006 inch)

After the piston rings have been installed, rotate the piston rings so that the end gaps are 120 degrees from each other.

(6) Piston skirt

Lubricate the entire piston in zone (A) prior to assembly into the cylinder block. Use clean engine oil.

Piston Pin Bore

(7) Piston pin

Piston pin bore diameter that is in the crown assembly without the bearing. ... 43.808 ± 0.008 mm (1.7247 ± 0.0003 inch)

Piston pin bore diameter that is in the piston skirt ... 40.020 ± 0.008 mm (1.5756 ± 0.0003 inch)

Piston pin diameter ... 39.993 ± 0.005 mm (1.5745 ± 0.0002 inch)

Length of piston pin ... 89.95 ± 0.15 mm (3.541 ± 0.006 inch)

Thoroughly lubricate the piston pin with clean engine oil prior to assembly.