Nissan 240SX/Altima 1993-1998 Repair Guide

Valve Lash

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INSPECTION



See Figures 1, 2 and 3



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Fig. Fig. 1: Check the valve clearance on these valves with the engine at TDC on the No. 1 cylinder



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Fig. Fig. 2: Check the valve clearance on these valves with the engine at TDC on the No. 4 cylinder (engine rotated 360 degrees)



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Fig. Fig. 3: Use a feeler gauge placed between the valve lifter and the camshaft to check valve lash

  1. Start engine and allow it to reach operating temperature.
  2.  
  3. Remove the cylinder head cover and all the spark plugs.
  4.  
  5. Set the No. 1 cylinder at TDC on its compression stroke. Align the pointer with the TDC mark on the crankshaft pulley. Check that the valve lifters on the No. 1 cylinder are loose and valve lifters on the No. 4 cylinder are tight. If not, turn the crankshaft one revolution (360 degrees) and align the pointer with the TDC mark on the crankshaft pulley.
  6.  
  7. Check the following valves:

    Both No. 1 intake valves.
     
    Both No. 1 exhaust valves.
     
    Both No. 2 intake valves.
     
    Both No. 3 exhaust valves.
     

  8.  
  9. Using a feeler gauge, measure the clearance between the valve lifter and the camshaft. Compare the measurements with the figures in the Engine Tune-Up Specifications Chart. Record any valve clearance measurements which are out of specification.
  10.  
  11. Turn the crankshaft one revolution (360 degrees) and align the mark on the crankshaft pulley with the pointer.
  12.  
  13. Check the following valves:

    Both No. 2 exhaust valves.
     
    Both No. 3 intake valves.
     
    Both No. 4 intake valves.
     
    Both No. 4 exhaust valves.
     

  14.  
  15. Using a feeler gauge, measure the clearance between the valve lifter and the camshaft. Compare the measurements with the figures in the Engine Tune-Up Specifications Chart. Record any valve clearance measurements which are out of specification.
  16.  
  17. If all the valve clearances are within specification, install the cylinder head cover and the spark plugs.
  18.  

ADJUSTMENT



See Figures 4, 5, 6, 7, 8 and 9



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Fig. Fig. 4: Place the depressor tool around the camshaft as illustrated



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Fig. Fig. 5: Place the keeper tool between the camshaft and valve lifter to retain the valve lifter



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Fig. Fig. 6: Remove the adjusting shim using a magnet



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Fig. Fig. 7: Determine replacement shim size by measuring the existing shim and adding the difference of the measured valve clearance and the specified valve clearance



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Fig. Fig. 8: The thickness of the shims, in millimeters, is stamped into the top of the shim



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Fig. Fig. 9: After inserting the new shim, install the depressor tool and the keeper tool. Then remove the keeper tool, followed by the depressor tool, and recheck the valve clearance

  1. Adjust the valves with the engine cold.
  2.  
  3. Turn the crankshaft so the camshaft lobe of the valve to be adjusted is pointed straight up.
  4.  
  5. Turn the lifter so the notch is pointed towards the center of the cylinder head; this will facilitate the shim removal process.
  6.  
  7. Using a depressor tool, push down on the lifter and insert a keeper tool on the edge of the lifter to keep the lifter in the depressed position.
  8.  
  9. Remove the depressor tool and remove the shim with a magnet.
  10.  
  11. Determine the replacement adjusting shim size by using the following procedures and formula:
    1. Using a micrometer determine thickness of the removed shim.
    2.  
    3. Calculate the thickness of a new adjusting shim so that valve clearance is within the specified values.

      R = thickness of the removed shim.
       
      N = thickness of the new shim.
       
      M = measured valve clearance.
       
      Formula: N = R + (M - valve clearance from Engine Tune-Up Specifications Chart)
       

    4.  

  12.  

  1. Shims are available in different sizes ranging from 0.0772-0.1055 in. (1.96-2.68mm), in increments of 0.0008 in. (0.02mm). The thickness is stamped on the shim; this side is always installed facing down. Select a new shim with a thickness as close as possible to the calculated value and install it in the lifter.
  2.  
  3. Install the new shim onto the lifter.
  4.  
  5. Depress the lifter and remove the keeper tool. Remove the depressor tool and recheck the valve clearance. Repeat this procedure for any other valves requiring adjustment.
  6.  
  7. Install the cylinder head cover and spark plugs when all valve adjustments are finished.
  8.  

 
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