GM Storm/Spectrum 1985-1993 Repair Guide

VALVE LASH

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ADJUSTMENT



Except Twin Camshaft Engine

See Figures 1 and 2

  1. Remove the cylinder head or valve cover; refer to Engine & Engine Rebuilding of this repair guide.
  2.  
  3. Rotate the engine in its normal direction of rotation until the notched line on the crankshaft pulley aligns with the 0 degree mark on the timing gear case. The position of the No. 1 piston should be at TDC of the compression stroke.
  4.  

The notch on the crankshaft pulley should align with the 0 degrees mark on the timing gear case. Make sure the rocker arms on the No. 1 cylinder are loose and the rockers on the No. 4 cylinder are tight. If not, turn the crankshaft one complete revolution and align the marks again.

  1. Check the valve lash between the rocker arm and valve stem on both the intake and exhaust valves on the number 1 cylinder, the intake valve(s) on the number 2 cylinder and the exhaust valve on the number 3 cylinder. If the valve lash on the intake valves is not 0.006 in. (0.15mm), adjust the valve lash. If the valve lash on the exhaust valve is not 0.010 in. (0.25mm), adjust the valve lash.
  2.  
  3. Adjust the valve lash by loosening the adjusting screw locknut and turning the adjusting screw until the proper specification is obtained. Tighten the adjusting screw locknut.
  4.  
  5. Set the intake valve to 0.006 in. (cold) for No. 1 and 2 cylinders; exhaust valves to 0.010 in. (cold) for No. 1 and 3 cylinders.
  6.  
  7. When the specified valves are adjusted, rotate the crankshaft 1 full revolution until the piston in the No. 4 cylinder is at TDC on compression stroke. (The No. 4 cylinder rockers will now be loose and the No. 1 rockers will be tight) set the intake valves to 0.006 in. (cold) for No. 3 and 4 cylinders; exhaust valves to 0.010 in. (cold) for No. 2 and 4 cylinders.
  8.  
  9. After the adjustment has been completed, install the head cover.
  10.  



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Fig. Fig. 1: Use a feeler gauge between the rocker arm and valve stem to properly adjust valve lash



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Fig. Fig. 2: Adjust only the specified valves when the engine is a No. 1 or No. 4 TDC of the compression stroke

1.6L Twin Camshaft Engine

See Figures 3, 4, 5 and 6

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the cylinder head or valve cover.
  4.  
  5. Position the No. 1 cylinder at TDC on its compression stroke.
  6.  

The notch on the crankshaft pulley should align with the 0 degrees mark on the timing gear case. Make sure the rocker arms on the No. 1 cylinder are loose and the rockers on the No. 4 cylinder are tight. If not, turn the crankshaft one complete revolution and align the marks again.

  1. Using a feeler gauge, measure the clearance between the cam lobe and the selective shim on the intake and exhaust valves on the No. 1 cylinder, then the intake valves on the No. 2 cylinder and the exhaust valves on the No. 3 cylinder. Note readings.
  2.  
  3. Rotate the crankshaft 360 degrees. Using a feeler gauge, measure the clearance between the cam lobe and the selective shim on the intake and exhaust valves on the No. 4 cylinder, then the intake valves on the No. 3 cylinder and the exhaust valves on the No. 2 cylinder. Note readings.
  4.  
  5. The valve clearance obtained on the exhaust valves should be between 0.008-0.012 in. (0.20-0.30mm). If not, replace the selective shim by turning the camshaft lobe downward and installing tool J-38413-2 or J-38413-3 (valve lash spring spacer) between the camshaft journal and the cam lobe next to the selective shim. Turn cam lobe upward and remove the selective shim. Install new shim using the selective shim chart.
  6.  

The rear camshaft bearing caps must be removed to remove the selective shim.

  1. The valve clearance obtained on the intake valves should be between 0.004-0.008 in. (0.10-0.20mm). If not, replace the selective shim by turning the camshaft lobe downward and installing tool J-38413-2 or J-38413-3 between the camshaft journal and the cam lobe next to the selective shim. Turn cam lobe upward and remove the selective shim. Install new shim using the selective shim chart.
  2.  
  3. When the adjustment is completed, install the cylinder head covers and connect the battery negative cable. Start the engine and check for leaks.
  4.  



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Fig. Fig. 3: Insert a valve lash spring spacer in order to remove the selective shim



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Fig. Fig. 4: Cut-away view of the hydraulic lifter and selective shim mounting



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Fig. Fig. 5: Size selection table - intake shim



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Fig. Fig. 6: Size selection table - exhaust shim

1.8L Twincam Engine

The 1992 and 1993 1.8L Storm engine is equipped hydraulic lifters which require no valve lash adjustment. If a tapping noise is noticed at idle, inspect the valve train components for excessive wear.

 
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