MBE 4000 – Section 1.22 Rocker Arm

Section 1.22
Rocker Arm

Perform the following procedures for removal and installation of the rocker arm:‪

Section 1.22.1
Rocker Arm Removal

Remove the rocker arm assembly as follows:‪

1. Remove the cylinder head cover on each cylinder head. Refer to "1.1.1 Removal of Cylinder Head Cover" .
2. Remove the rocker arm assembly. See Figure "Rocker Assembly" .
   

   1. Cylinder Head Cover‪	3. Rocker Arm Assembly‪	5. Exhaust Valve Bridge‪
   2. Rocker Arm Mounting Bolt‪	4. Intake Valve Bridge‪	6. Pushrod‪

   Figure 1. Rocker Assembly

   1. Loosen the each valve lash adjusting screw.
   2. Remove each rocker arm mounting bolt.
   3. If removing more than one rocker arm assembly, mark the assembly with a paint pen to identify it on installation.
   4. Remove the rocker arm assembly from the cylinder head.
3. Inspect the rocker arm assembly for wear. If necessary, disassemble the rocker arm assembly and replace any worn parts. Refer to "1.22.2 Rocker Arm Disassembly" .
4. Measure each rocker arm mounting bolt. Replace each bolt longer than 91 mm (3.6 in.), as listed in Table "Specifications, Rocker Arm Mounting Bolts" .

   Size ‪	Max. Shaft Length: mm (in.) ‪	Torque Value: N·m (lb·ft) ‪
   M12‪	91 (3.6)‪	60 (44)‪ then an additional 90°‪

   Table 2. Specifications, Rocker Arm Mounting Bolts
5. Remove the valve bridge from each set of valves, intake and exhaust.
6. Inspect the valve bridges for wear. If necessary, replace any worn valve bridge(s).

Section 1.22.2
Rocker Arm Disassembly

Disassemble the rocker arm unit as follows:‪

1. Remove the rocker arm assembly from the cylinder head. Refer to "1.22.1 Rocker Arm Removal" .
2. Remove the snap rings from each end of the rocker arm shaft. See Figure "Rocker Arm Components" .
   

   1. Snap Ring‪	4. Rocker Support‪	7. Adjusting Screw‪
   2. Washer‪	5. Intake Rocker Arm‪
   3. Exhaust Rocker Arm‪	6. Locknut‪

   Figure 2. Rocker Arm Components

3. Remove the rocker arms and washers from the shafts on each end of the rocker arm support. Keep all parts in order, as removed, for ease of assembly.
   1. Remove the intake rocker arm and washer.
   2. Remove the exhaust rocker arm and washer.
   3. Remove the adjusting screw and locknut from both intake and exhaust rocker arms.
   4. Mark each rocker arm and shaft with paint pens, for ease of installation.
4. Inspect the parts of the rocker arm assembly for wear, and replace if necessary.

Section 1.22.3
Rocker Arm Assembly

Assemble the rocker arm unit as follows:‪

1. Install the adjusting screw and locknut on both intake and exhaust rocker arms. Tighten the locknut 50 N·m (37 lb·ft).
2. Inspect the inside diameter of the rocker arm bushing. Replace the rocker arm bushing if the inside diameter is smaller than 25.005 mm (0.9844 in.) or larger than 25.021 mm (0.9851 in.) as listed in Table "Rocker Arm Bushing Specifications" .

   Description ‪	Specification: mm (in.) ‪
   Bushing Inside Diameter (when installed)‪	25.005-25.021 (0.9844-0.9851)‪
   Shaft Diameter‪	24.967-24.980 (0.9830-0.9835)‪

   Table 4. Rocker Arm Bushing Specifications
3. Inspect the diameter of the rocker arm shaft. Replace the rocker arm shaft if the diameter is smaller than 24.967 mm (0.9830 in.) or larger than 24.980 mm (0.9835 in.).
4. Lubricate the washers, rocker arm bushings, and the shafts of the support with a light coating of engine oil.
5. Install the rocker arms and washers on the correct rocker arm shaft, as marked on removal. Make sure both intake and exhaust rocker arms are installed correctly.
6. When the assembly is complete, secure the assembly by installing a snap ring on the end of each rocker arm shaft.

Section 1.22.4
Rocker Arm Installation

Install the rocker arm unit as follows:‪

1. Install a valve bridge on each set of valves, both intake and exhaust.
2. Lubricate each pushrod with a light coating of engine oil.
3. Inspect each pushrod to be sure it is correctly seated in its tappet. Replace any pushrods that are warped, are not correctly seated, or are not the correct length as listed in Table "Rocker Arm Specifications" .

   Description ‪	Stage ‪	Specification: mm (in.) ‪
   Outside Diameter of Valve Tappets‪	Normal‪	29.931-29.952 (1.1784-1.1792)‪
   Outside Diameter of Valve Tappets‪	Repair Stage I‪	30.444-30.465 (1.1986-1.1994)‪
   Diameter of Tappet Seats (in cylinder block)‪	Normal‪	30.000-30.021 (1.1811-1.1819)‪
   Diameter of Tappet Seats (in cylinder block)‪	Repair Stage I‪	30.500-30.525 (1.2008-1.2018)‪
   Total Length of Pushrods‪		345.0-346.5 (13.58-13.64)‪
   Maximum Pushrod Warpage‪		0.5 (0.02)‪
   Maximum Length of Rocker Arm Mounting Bolts‪		91 (3.6)‪

   Table 5. Rocker Arm Specifications
4. Install the rocker arm assembly.
   1. Position the rocker arm assembly on the cylinder head, as removed.
   2. Install the mounting bolts in the holes in the cylinder head.
   3. Tighten each mounting bolt 60 N·m (44 lb·ft). Final angular tightening: 90 degrees.
5. Adjust the valve lash. Refer to "1.20.3 Valve Lash Adjusting" .
6. Install the cylinder head cover on each cylinder head. Refer to "1.1.2 Installation of Cylinder Head Cover" .