Check and Adjust Valve Clearance

RG7408
RG7408-UN-06AUG96

Flywheel Housing Timing Holes

A - Timing/Rotation Hole

B - Timing Pin Hole

CAUTION: To prevent accidental starting of engine while performing valve adjustments, always disconnect NEGATIVE (—) battery terminal.

IMPORTANT: Valve clearance MUST BE checked and adjusted with engine COLD.

  1. Remove rocker arm cover and crankcase ventilator tube.

  2. IMPORTANT: Visually inspect contact surfaces of valve tips and rocker arm wear pads. Check all parts for excessive wear, breakage, or cracks. Replace parts that show visible damage.

    Rocker arms that exhibit excessive valve clearance should be inspected more thoroughly to identify damaged parts.

    Remove plastic plugs or cover plate from engine timing/rotation hole (A) and timing pin hole (B).

  3. NOTE: Some engines are equipped with flywheel housings which do not allow use of an engine flywheel rotation tool. These engines may be rotated from front nose of engine, using JDG966 Crankshaft Front/Rear Rotation Adapter.

    Using JDE83 or JDG281A Flywheel Turning Tool, rotate engine flywheel in running direction (clockwise viewed from front) until No. 1 cylinder is at TDC compression stroke. Insert JDG1571 Timing Pin in flywheel.

    If No.1 cylinder rocker arms are loose, the engine is at No. 1 TDC compression.

    If No. 1 cylinder rocker arms are not loose, rotate engine one full revolution (360°) to No. 1 TDC compression.


  4. RG7409
    RG7409-UN-06AUG96

    Adjusting Valves

    A - Adjusting Screw Jam Nut

    Adjust valves to following specifications using the valve clearance adjustment procedure described below. Loosen the jam nut (A) on rocker arm adjusting screw. Turn adjusting screw until feeler gauge slips with a slight drag. Hold the adjusting screw from turning with screwdriver and tighten jam nut to specifications. Recheck clearance again after tightening jam nut. Readjust clearance as necessary.

    ItemMeasurementSpecification
    Intake Valve Clearance Adjustment (Rocker Arm-to-Valve Tip) (Engine Cold)Clearance0.36 mm (0.014 in.)
    Exhaust Valve Clearance Adjustment (Rocker Arm-to-Valve Tip) (Engine Cold)Clearance0.46 mm (0.018 in.)
    Rocker Arm Adjusting Screw Jam NutTorque27 N˙m (20 lb-ft)



4-Cylinder Engine

RG4776
RG4776-UN-31OCT97

4-Cylinder Engine Valve Adjustment

A - Front of Engine

B - No. 1 Piston at TDC Compression Stroke

C - No. 4 Piston at TDC Compression Stroke

E - Exhaust Valve

I - Intake Valve

NOTE: Firing order is 1-3-4-2.

Lock No. 1 piston at TDC compression stroke (B).

Adjust valve clearance on No. 1 and 3 exhaust valves and No. 1 and 2 intake valves.

Rotate flywheel 360°. Lock No. 4 piston at TDC compression stroke (C).

Adjust valve clearance on No. 2 and 4 exhaust valves and No. 3 and 4 intake valves.


6-Cylinder Engine

RG4777
RG4777-UN-31OCT97

6-Cylinder Engine Valve Adjustment

A - Front of Engine

B - No. 1 Piston at TDC Compression Stroke

C - No. 6 Piston at TDC Compression Stroke

E - Exhaust Valve

I - Intake Valve

NOTE: Firing order is 1-5-3-6-2-4.

Lock No. 1 piston at TDC compression stroke (B).

Adjust valve clearance on No. 1, 3, and 5 exhaust valves and No. 1, 2, and 4 intake valves.

Rotate flywheel 360°. Lock No. 6 piston at TDC compression stroke (C).

Adjust valve clearance on No. 2, 4, and 6 exhaust valves and No. 3, 5, and 6 intake valves.


The Following Steps Are to Install the Rocker Arm Cover Gasket

IMPORTANT: Replace rocker arm cover gasket every time the rocker arm cover is removed.

NOTE: The procedure shown is for the 4045 engine. The 6068 engine is similar.

NOTE: This procedure is to install a standard or a high-temperature rocker arm cover gasket. Use the appropriate procedure.

NOTE: For extended high temperature operations, the optional high temperature gasket kit is available to prevent oil leakage between valve cover and head, in the area above the exhaust ports and/or directly beneath the turbo.

NOTE: Extended high temperature rocker arm cover gasket (optional) is designed for non-High Pressure Common Rail (HPCR) engines.

  • Carefully remove the old gasket from rocker arm cover. Do not use any cutting tool that could damage the cover.
  • Clean the groove with acetone. Dry with compressed air.
  • Clean the mating surface of cylinder head.

Rocker Arm Cover Gap Adjustment for High-Temperature Gasket

IMPORTANT: Installation of the high-temperature rocker arm cover gasket requires the measurement/adjustment of the gap between the rocker arm cover and the cylinder head.

  1. RG27005
    RG27005-UN-08APR15

    Rocker Arm Cover Assembly

    A - Plug (4 used)

    B - Flanged Head Nut (4 used)

    C - O-Ring (4 used)

    D - Rocker Arm Cover

    E - Rocker Arm Cover Gasket

    Install rocker arm cover (D) without gasket (E) or O-rings (C).


  2. RG33390
    RG33390-UN-27JAN21

    Tightening Sequence

    Install flanged head nuts (B) and tighten in sequence shown to specification.

    ItemMeasurementSpecification
    Rocker Arm Cover NutsTorque35 N·m (26 lb·ft)


  3. RG27006
    RG27006-UN-08APR15

    Rocker Cover Gap

    A - Rocker Arm Cover

    B - Gap

    C - Cylinder Head

    Use a feeler gauge to measure the gap (B) between the rocker arm cover (A) and the cylinder head (C).


  4. Remove rocker arm cover from an engine.

  5. RG27007
    RG27007-UN-08APR15

    D - Hold-Down Stud

    E - Shim

    If gap (B) measured in Step 3 is less than 1.5 mm (0.059 in), install one shim (E) onto each rocker arm cover hold down stud (D).


  6. If the gap measured in Step 3 is greater than 1.5 mm (0.059 in), do not install any shims.


Rocker Arm Cover Gasket Installation

  1. RG27005
    RG27005-UN-08APR15

    Rocker Arm Cover Assembly

    A - Plug (4 or 6 used)

    B - Flanged Head Nut (4 or 6 used)

    C - O-Ring (4 or 6 used)

    D - Rocker Arm Cover

    E - Rocker Arm Cover Gasket

    Install a new rocker arm cover gasket (E) in the groove at the base of rocker arm cover (D). Start at the ends and work toward the center of the cover. Do not use sealant on the gasket (E).


  2. IMPORTANT: Prevent damage to engine components. ALWAYS discard O-rings when removed. Reuse of O-rings can cause leakage.

    Install rocker arm cover (D) onto the cylinder head over the studs of the rocker arm shaft retaining cap screws. Install O-rings (C) onto the studs.

  3. IMPORTANT: The Non-High Pressure Common Rail (HPCR) engines require a different tightening specification. Use the appropriate torque value for the engine.

    RG33390
    RG33390-UN-27JAN21

    Tightening Sequence 4045 Engine

    RG33483
    RG33483-UN-18FEB21

    Tightening Sequence 6068 Engine

    Install flanged head nuts (B) onto the studs of the rocker arm shaft retaining cap screws. Tighten in sequence shown to specification.

    ItemMeasurementSpecification
    Rocker Arm Cover Nuts
    Non-HPCR Engines with 2-Valve HeadTorque35 N·m (26 lb·ft)
    HPCR Engines with 2-Valve HeadTorque11 N·m (97 lb·in)


  4. Install plugs (A).

OUOD006,00000E3-19-20210218