Isuzu Cars and Trucks 1981-1991

Valve Lash

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adjustment
All Engines Except 4XE1 (1.6L DOHC) and V6

NOTE
The valves are adjusted with the engine COLD. It is best to allow an engine to sit overnight before beginning a valve adjustment. While all valve adjustments must be made as accurately as possible, it is better to have the adjustment slightly loose rather than slightly tight. A burned valve may result from overly tight valve adjustments.

  1. Remove the rocker arm cover and discard the gasket.
  2.  
  3. Make sure both the cylinder head and camshaft retaining bolts are tightened to the proper torque.
  4.  
  5. Rotate the crankshaft pulley until the No. 1 piston is at TDC of the compression stroke.
  6.  



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Fig. Valve adjustment procedure


NOTE
To make sure the piston is on the correct stroke, remove the spark plug and place a finger over the hole. Feel for air being forced out of the spark plug hole. Both valves on No. 1 cylinder will be closed. Stop turning the crankshaft when the TDC timing mark on the crankshaft pulley is directly aligned with the timing mark pointer.

  1. With the No. 1 piston at TDC of the compression stroke, adjust the clearance according to the "Valve Adjusting Sequence" illustrations in this section.
  2.  



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Fig. Valve adjusting sequence all 4-cylinder gasoline engines



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Fig. Valve adjusting sequence 4FB1 diesel engines



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Fig. Valve adjusting sequence C223 and C223-T diesel engines

  1. Adjust the clearance by loosening the locknut and turning the adjusting screw. Retightening the locknut when the proper thickness feeler gauge passes between the camshaft or valve stem and has a slight drag when the clearance is corrected.
  2.  
  3. Rotate the crankshaft 1 complete revolution (360and#x00B0;) to position the No. 4 piston at TDC of its compression stroke and adjust the clearances as shown in the illustration.
  4.  
  5. After adjustment, use a new gasket, sealant and install the rocker arm cover.
  6.  

4XE1-WT (DOHC) Engine

NOTE
Inspect and adjust the valve clearance when the engine is COLD. Retorque the camshaft bearing cap bolts to 7 ft. lbs. (10 Nm) before inspecting and adjusting valve clearance.

  1. Remove the cylinder head cover.
  2.  
  3. Remove the spark plugs.
  4.  



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Fig. Press down the tappet by the cam lift, turning camshaft and place the spacer on the upper circumference o the tappet from outside of the cylinder head



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Fig. Release cam lift by turning the camshaft and hold the tappet down with the spacer. Remove the adjuster shim from the spark plug side with a small prybar and magnetic finger



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Fig. Valve adjusting sequence 4XE1-WT (DOHC) engine



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Fig. Adjuster shim selection chart (intake)



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Fig. Adjuster shim selection chart (exhaust)

  1. Set the No. 1 cylinder to TDC on the compression stroke by turning the crankshaft pulley and align the notched line with the 0 mark on the timing cover. Check that the tappets on the No. 1 have play and tappets on the No. 4 have no play. If not, turn the crankshaft one revolution and align the marks as above.
  2.  
  3. The allowable valve clearance is 0.004 and 190.008 in. (0.10 and 190.20mm) for intake and 0.008 and 190.012 in. (0.20 and 190.30mm).
  4.  
  5. Measure the clearance between the cam lobe and adjuster (shim) of the valves. Refer to "Valve Adjuster Sequence" illustration in the section.
  6.  
  7. Record the measurements which are out of the allowable clearance.
  8.  
  9. Turn the crankshaft one revolution and measure the remaining valves, refer to the "Valve Adjuster Sequence" illustration.
  10.  
  11. The valves are adjusted by replacing the shims.
  12.  
  13. Press down the tappet by the cam lift, turning the camshaft. Place the spacer tool J-38413-2 on the upper circumference of the tappet from the outside of the cylinder head.
  14.  
  15. Release the cam lift by turning the camshaft and hold the tappet down with the spacer tool. Remove the shim from the spark plug side with a small prybar or magnetic finger. Use the cutaway in the tappet to remove the shim.
  16.  
  17. Determine the thickness of the shim by using the following formula and accompanying charts:
  18.  
    1. Measure the thickness of the original shim with a micrometer.
    2.  
    3. Calculate the thickness of an available shim so that the valve clearance comes within the allowable value.
    4.  
    5. Ta = thickness of the available shim
    6.  
    7. M = measured valve clearance
    8.  
    9. To = thickness of original shim
    10.  
    11. M + To = Ta
    12.  
    13. Select the available shim with a thickness as close as possible to the calculated values.
    14.  

  19. Install the shim by placing it into the tappet. Press down the tappet by turning the camshaft and remove the spacer tool.
  20.  
  21. Install the cylinder head cover.
  22.  

V6 Engines
  1. Remove the rocker arm cover.
  2.  
  3. Rotate the crankshaft until the No. 1 cylinder is on TDC of its compression stroke.
  4.  


NOTE
When the notch on the damper pulley is aligned with the 0 timing mark and the rocker arms of the No. 1 cylinder do not move, the engine is at TDC of the compression stroke of the No. 1 cylinder.

  1. With the engine at TDC of the No. 1 cylinder, adjust the following valves:
  2.  
    1. Exhaust: 1, 2 and 3
    2.  
    3. Intake: 1, 5 and 6
    4.  

  3. Back out the adjusting nut until lash is felt.
  4.  
  5. Tighten the adjusting nut until the lash is removed, then, turn the nut 1 1 / 2 additional turns to center the lifter plunger.
  6.  
  7. Rotate the engine 1 complete revolution and reposition the notch on the damper pulley with the 0 make on the timing tab. this is the No. 4 firing position.
  8.  
  9. With the engine at TDC of the No. 4 cylinder, adjust the following valves:
  10.  
    1. Exhaust: 4, 5 and 6
    2.  
    3. Intake: 2, 3 and 4
    4.  

  11. Back out the adjusting nut until lash is felt.
  12.  
  13. Tighten the adjusting nut until the lash is removed, plus, turn the nut 1 1 / 2 additional turns to center to lifter plunger.
  14.  
  15. Using a new gasket and sealant, install the rocker arm cover.
  16.  



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Fig. Valve adjustment procedure V6 engine

 
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