3126 Truck Engine Caterpillar

Illustration 1	g00439604

Note: The inlet and exhaust valve stems must be coated with engine oil prior to installation in the cylinder head.

Note: The tips of the inlet and exhaust valves must be coated with 8T-2998 Lubricant . The lubricant must be applied after assembly of the retainer.

(1) Exhaust valve

(2) Inlet valve

(3) 6I-2307 Spring for exhaust valve

Free length ... 81.0 mm (3.19 inch)

Assembled length ... 70.8 mm (2.79 inch)

Load at assembled length ... 612 ± 31 N (138 ± 7 lb)

Minimum operating length ... 59 mm (2.30 inch)

Load at minimum operating length ... 1325 ± 66 N (298 ± 15 lb)

(4) 7C-4273 Spring for inlet valve

Free length ... 71 mm (2.80 inch)

Assembled length ... 65.9 mm (2.60 inch)

Load at assembled length ... 217 ± 22 N (49 ± 5 lb)

Minimum operating length ... 51 mm (2.0 inch)

Load at minimum operating length ... 858 ± 43 N (193 ± 10 lb)

(5) Height to the top of the valve guides ... 23 ± 0.50 mm (0.906 ± 0.020 inch)

Diameter of valve guide ... 12.065 mm (0.4750 inch)

Note: Install the valve guide from the spring side of the cylinder head.

Note: Assemble the valve guide. Seat the seal against the top of the valve guide.

(6) Valve stem diameter ( new ) ... 8.000 ± 0.008 mm (0.3150 ± 0.0003 inch)

The cylinder head valves can be reused if the minimum dimensions for the valve stems are met.

Minimum diameter of a valve stem ( worn ) ... 7.965 mm (0.3136 inch)

After installation into the cylinder head, the valve guide bore is the following value.

Diameter of the valve guide bore ( new ) ... 8.072 ± 0.013 mm (0.3178 ± 0.0005 inch)

The valve guide can be reused. The valve guide bore must not be larger than the following value.

Maximum diameter of a valve guide bore ( worn ) ... 8.080 mm (0.3181 inch)

(7) Diameter of the valve head

Inlet valve ... 47.00 ± 0.13 mm (1.850 ± 0.005 inch)

Exhaust valve ... 40.00 ± 0.13 mm (1.575 ± 0.005 inch)

(8) Angle of the valve faces

Inlet valve ... 29.75 ± 0.25 degrees

Exhaust valve ... 45 ± 0.25 degrees

Illustration 2	g00291916

(9) Diameter of the valve seat inserts

Inlet valve ... 50.000 ± 0.013 mm (1.9685 ± 0.0005 inch)

Exhaust valve ... 43.000 ± 0.013 mm (1.6929 ± 0.0005 inch)

Diameter of the bore in cylinder head for the valve seat insert

Bore diameter

Inlet valve ... 49.931 ± 0.013 mm (1.9658 ± 0.0005 inch)

Exhaust valve ... 42.931 ± 0.013 mm (1.6902 ± 0.0005 inch)

Note: The valve seat insert must be shrunk by reduced temperature before installing in the head.

(10) Angle of the valve seat inserts

Inlet valve ... 30.25 ± 0.50 degrees

Exhaust valve ... 45.5 ± 0.50 degrees

(11) Depth of the bore in the head for the valve seat insert ... 10.00 ± 0.13 mm (0.394 ± .005 inch)

(12) Outside diameter of the seating face of the valve seat insert

Inlet valve ... 44.029 ± 0.085 mm (1.7334 ± 0.0033 inch)

Exhaust valve ... 38.077 ± 0.046 mm (1.4991 ± 0.0018 inch)

Note: Do not reuse the valve seat inserts if the outside diameter of the valve seat insert is larger than the specified value.

(13) The valve lips can be reused if the minimum dimensions for the valve lips are met.

Inlet valve ... 1.80 mm (0.071 inch)

Exhaust valve ... 1.50 mm (0.059 inch)

(14) Distance from the head of the valve to the cylinder head face. The valve must be closed.

Inlet valve

Maximum permissible distance ... 2.05 mm (0.081 inch)

Minimum permissible distance ... 1.13 mm (0.045 inch)

Exhaust valve

Maximum permissible distance ... 2.85 mm (0.112 inch)

Minimum permissible distance ... 1.50 mm (0.059 inch)