Finding Top Center Position for No. 1 Piston

SMCS - 1105-531

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Table 1
Needed Tools
9S-9082 / Engine Turning Tool / 1

The No. 1 piston at top center (TC) on the compression stroke is the starting point of all timing procedures.

Note: Some engines have two threaded holes in the flywheel. These holes are in alignment with the holes with plugs in the left and right front of the flywheel housing. The two holes in the flywheel are at a different distance from the center of the flywheel so the timing bolt cannot be put in the wrong hole.

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  1. Timing bolt (1) is a cover bolt. The timing bolt can be installed in either the left side of the engine at location (2) or in the right side of the engine at timing bolt location (4) . Remove both bolts (1) and cover (3) from the flywheel housing. Remove the plug from the timing hole in the flywheel housing.
  1. Put timing bolt (1) (long bolt that holds the cover on the flywheel housing) through the timing hole in the flywheel housing. The 9S-9082 Engine Turning Tool and a 1/2 inch drive ratchet wrench are used in order to turn the engine flywheel in the direction of normal engine rotation. Normal engine rotation is counterclockwise. Normal engine rotation is viewed from the flywheel end of the engine. Turn the engine flywheel until the timing bolt engages with the threaded hole in the flywheel

Electronic Unit Injector - Adjust

SMCS - 1290-025

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Table 1
Required Tools
Part Number / Part Name / Quantity
9U-7227 / Injector Height Gauge / 1

Note: Determine the style of variable valve actuator that is installed on the engine. For the BXS engines, remove the variable valve actuators. For the MXS engines, it is not necessary to remove the variable valve actuators.

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(1) Rocker arm
(2) Adjustment screw
(3) Locknut
(4) 9U-7227 Injector Height Gauge

To make an adjustment to the unit injectors on cylinders 3, 5, and 6 use the following procedure:

  1. Put the No. 1 piston at the top center position on the compression stroke. Refer to Testing and Adjusting, "Finding Top Center Position for No. 1 Piston".
  1. Injector height gauge (4) is used in order to obtain a dimension of 78.0 ± 0.2 mm (3.07 ± 0.01 inch). The dimension is measured from the top of the unit injector to the machined ledge of the fuel injector body.
  1. Turn unit injector adjustment screw (2) clockwise until the correct height is obtained.
  1. Hold the adjustment screw in this position and tighten locknut (3) to a torque of 100 ± 10 N·m (74 ± 7 lb ft).
  1. To make an adjustment to the unit injectors on cylinders 1, 2, and 4, remove the timing bolt. Turn the flywheel by 360 degrees in the direction of engine rotation. The direction of engine rotation is counterclockwise, as the engine is viewed from the flywheel end. This will put the number 1 piston at the top center position on the exhaust stroke.
  1. Repeat Steps 3 through 4.
  1. Remove the timing bolt from the flywheel after all the unit injector adjustments have been made. Reinstall the valve mechanism cover.

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Engine Valve Lash - Inspect/Adjust

Valve Lash Check

An adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. Check the valve lash while the engine is stopped. The range is specified in Table 1.

Table 1
Valve Lash
Valves / Acceptable Range for Valve Lash
Inlet /
0.38 ± 0.08 mm (0.015 ± 0.003 inch)
Exhaust /
0.76 ± .08 mm (0.030 ± 0.003 inch)

If the measurement is not within this range adjustment is necessary. Refer to Testing And Adjusting, "Valve Lash Adjustment".

Valve Lash Adjustment

(A) Inlet valves

(B) Exhaust valves

(C) Left side of the engine

(D) Cylinder number

(E) Front of the engine

(F) Flywheel end of the engine

(G) Right side of the engine

Adjust the valve lash while the engine is stopped. Use the following procedure in order to adjust the valves:

  1. Determine the style of variable valve actuator that is installed on the engine.
  2. For the BXS engines, remove the variable valve actuators.
  3. For the, MXS engines, it is not necessary to remove the variable valve actuators.
  1. Put the No. 1 piston at the top center position. See Testing and Adjusting, "Finding Top Center Position for No. 1 Piston" for further details.

Note: If the engine is equipped with an engine compression brake, loosen the adjustment screw for the lash on the slave piston for the compression brake prior to adjusting the engine valve lash. Refer to the Testing and Adjusting, "Slave Piston Lash - Adjust" topic in order to adjust the slave piston lash.

  1. With No. 1 piston at the top center position of the compression stroke, an adjustment can be made to the valves.

Before any adjustments are made, lightly tap each rocker arm at the top of the adjustment screw. Use a soft mallet to ensure that the lifter roller seats against the camshaft's base circle.

  1. Make an adjustment to the valve lash on the inlet valves for cylinders 1, 2, and 4.
  2. Loosen valve adjustment locknut (3) .
  3. Place the appropriate feeler gauge (5) between the inlet rocker arm and the inlet valve bridge. Turn inlet adjustment screw (4) while valve adjustment locknut (3) is being held from turning. Adjust the valve lash until the correct specification is achieved. Refer to Table 2.
  4. After each adjustment, tighten valve adjustment locknut (3) while valve adjustment screw (4) is being held from turning. Tighten to a torque of 30 ± 7 N·m (22 ± 5 lb ft). Recheck each adjustment.
  1. Make an adjustment to the valve lash on the exhaust valves for cylinders 1, 3, and 5.
  2. Loosen valve adjustment locknut (1) .
  3. Place the appropriate feeler gauge (5) between the exhaust rocker arm and the exhaust valve bridge. Turn exhaust adjustment screw (2) while valve adjustment locknut (1) is being held from turning. Adjust the valve lash until the correct specification is achieved. Refer to Table 2.
  4. After each adjustment, tighten valve adjustment locknut (1) while valve adjustment screw (2) is being held from turning. Tighten to a torque of 30 ± 7 N·m (22 ± 5 lb ft). Recheck each adjustment.
  1. Remove the timing bolt, and turn the flywheel by 360 degrees in the direction of engine rotation. This will position the No. 6 piston at the top center on the compression stroke. Install the timing bolt in the flywheel.
  1. Make an adjustment to the valve lash on the inlet valves 3, 5, and 6.
  2. Loosen valve adjustment locknut (3) .
  3. Place the appropriate feeler gauge (5) between the inlet rocker arm and the inlet valve bridge. Turn inlet adjustment screw (4) while valve adjustment locknut (3) is being held from turning. Adjust the valve lash until the correct specification is achieved. Refer to Table 2.
  4. After each adjustment, tighten valve adjustment locknut (3) while valve adjustment screw (4) is being held from turning. Tighten to a torque of 30 ± 7 N·m (22 ± 5 lb ft). Recheck each adjustment.
  1. Make an adjustment to the valve lash on the exhaust valves 2, 4, and 6.
  2. Loosen valve adjustment locknut (1) .
  3. Place the appropriate feeler gauge (5) between the exhaust rocker arm and the exhaust valve bridge. Turn exhaust adjustment screw (2) while valve adjustment locknut (1) is being held from turning. Adjust the valve lash until the correct specification is achieved. Refer to Table 2.
  4. After each adjustment, tighten valve adjustment locknut (1) while valve adjustment screw (2) is being held from turning. Tighten to a torque of 30 ± 7 N·m (22 ± 5 lb ft). Recheck each adjustment.
  1. Remove the timing bolt from the flywheel after all valve lash adjustments have been made.

Refer to the Testing and Adjusting, "Slave Piston Lash - Adjust" topic for information on adjusting the slave piston lash.

Note: The engine valve lash must be adjusted before you adjust the compression brake.

The lash must also be adjusted on the electronic unit injector. Refer to Testing and Adjusting, "Electronic Unit Injector - Adjust" for more information.

Variable Valve Actuators - Inspect/Adjust

The following procedure should be followed when variable valve actuators (2) have been removed from the engine.

  1. Loosen jam nut (1) .

NOTICE
Do not turn the cylinders clockwise. If you turn the cylinders clockwise, the piston assembly will fall out of the housing. If the piston assembly falls out of the housing, damage to the piston will occur.
  1. Turn the cylinders (2) counterclockwise until the cylinders reach the stop.

Note: Do not force the cylinders. Damage will occur to the cylinders.

  1. Install the variable valve actuators onto the cylinder head. Refer to the Specifications manual for the proper torque sequence.
  1. Set cylinder 1 at the top center position. See Testing and Adjusting, "Finding Top Center Position for the No. 1 Piston" for details on this procedure.

Note: The inlet valves should be fully closed. The rocker arm should rest on the base circle of the camshaft lobe.

  1. Set lash (3) on the following cylinders: 1, 2 and 4. Refer to Specifications, "Variable Valve Actuators" for the amount of lash.
  2. Place the feeler gauge between the piston pin and the rocker arm.

Note: The inlet rocker arm must be in contact with valve bridge (4) when you set the lash for variable valve actuators.

  1. Turn the cylinder clockwise until the feeler gauge fits snugly between the piston and the rocker arm.
  2. Tighten jam nut (1). Refer to Specifications, "Variable Valve Actuators" for the proper torque for the jam nut.
  1. Turn the crankshaft clockwise by 360 degrees. This will position the No. 6 piston at the top center on the compression stroke. Install the timing bolt in the flywheel.
  1. Repeat Step 5 for the following cylinders: 3, 5 and 6.
  1. Connect the proper wiring harness to each solenoid.

Compression Brake Lash - Adjust

The engine valve lash and the injector lash must be within specifications prior to adjusting the lash for the CAT compression brake. Refer to Testing and Adjusting, "Engine Valve Lash - Inspect/Adjust" for the correct procedure for inspection of the engine valve lash. Refer to Testing and Adjusting, "Electronic Unit Injector - Adjust" for the proper procedure for inspection of the injector lash adjustment.

Note: Adjustment of the lash for the CAT compression brake must be performed while the engine is cold. If the engine is warm, allow the engine to cool prior to performing the following adjustments.

Note: The lash is measured between the rod for the CAT compression brake and the exhaust rocker arm. Make all adjustments while the engine is stopped and the exhaust valves are closed.

Use the following procedure to adjust the slave piston lash on cylinders 1, 3, and 5:

(1) Adjustment screw
(2) Adjustment screw locknut
(3) Rod for the CAT compression brake
(4) Exhaust rocker arm
  1. Put the No. 1 piston at the top center position on the compression stroke. Refer to Testing and Adjusting, "Finding Top Center Position for No. 1 Piston".
  1. Loosen adjustment screw locknut (2) and back out adjustment screw (1) until the CAT Compression Brake rod is not in contact with the exhaust rocker arm.
  1. Make sure that the rod for the CAT compression brake is centered in the housing. Set the lash to 0.686 ± 0.050 mm (0.0270 ± 0.0020 inch). Place the appropriate feeler gauge between the rod for the CAT compression brake and the exhaust rocker arm. Turn the adjustment screw in a clockwise direction. Slide the feeler gauge between the rod for the CAT compression brake and the exhaust rocker arm. Continue turning the adjustment screw until a slight drag is felt on the feeler gauge. Remove the feeler gauge.
  1. Torque the adjustment screw locknut. Tighten the locknut to 15 ± 3 N·m (11 ± 2 lb ft).
  1. Recheck the lash setting after you torque the locknut.
  1. Remove the timing bolt and turn the flywheel by 360 degrees in the direction of engine rotation. This will put the No. 6 piston at the top center position on the compression stroke. Install the timing bolt in the flywheel. To adjust the slave piston lash on cylinders 2, 4, and 6, perform Steps 2 through 5.
  1. Remove the timing bolt from the flywheel after all adjustments have been performed. Reinstall the timing cover.