Camshaft And Cylinder Head Inspection (SOHC)

TOOLS REQUIRED:

SA91101NE Feeler Gauge
SA91102NE Gauge Ball Set
SA9177NE Straight Edge (24")
SA9179NE Dial Indicator

Remove camshaft. Using a punch and hammer, remove the rear camshaft plug, if not removed previously, by driving it inward.

Fig 1: Removing Camshaft
Courtesy of GENERAL MOTORS CORP.
Measure the camshaft thrust (end play). Install the camshaft, thrust plate, and camshaft timing sprocket. Using a Dial Indicator SA9179NE (or equivalent), measure the thrust clearance while moving the camshaft back and forth. If clearance is greater than maximum, replace the thrust plate and/or camshaft.
Camshaft Thrust Clearance
1. Standard: 0.070-0.200 mm (0.028-0.0079 in.)
2. Service Limit: 0.250 mm (0.0098 in.) max.
NOTE: If the camshaft is not removed through the rear of the cylinder head, an impact driver and T-40 TORX™ must be used to loosen the thrust plate retaining screws. TORX™ screws (are usually damaged during removal and) should be replaced.
Remove camshaft from camshaft housing:
1. Remove the timing chain sprocket and thrust plate.
  
  Fig 2: Timing Chain Sprocket And Thrust Plate
  Courtesy of GENERAL MOTORS CORP.
2. Turn the camshaft slowly while removing it in order to prevent damage to the camshaft housing.
  
  Fig 3: Turning Camshaft
  Courtesy of GENERAL MOTORS CORP.
Inspect camshaft:
1. Place the camshaft ends in V-blocks and, using a dial indicator or service tool SA9179NE (or equivalent), measure the total runout at the center journal. If the runout is greater than maximum, replace the camshaft.
  
  Fig 4: Inspecting Camshaft
  Courtesy of GENERAL MOTORS CORP.
  
  Circle Total Runout
  1. Standard: 0.05 mm (0.0020 in.) max.
  2. Service Limit: 0.07 mm (0.0028 in.) max.
2. Using a dial indicator, measure the cam lobe lift rise. Place the camshaft in V-blocks located next to the lobe being measured. If the cam lobe lift rise is less than minimum, replace the camshaft.
  
  Fig 5: Measuring Cam Lobe Lift Rise
  Courtesy of GENERAL MOTORS CORP.
  
  Cam Lobe Lift Rise (Intake and Exhaust)
  1. Standard: 6.428-6.493 mm (0.2531-0.2556 in.)
  2. Service Limit: 6.400 mm (0.2520 in.) min.
    
    Fig 6: Measuring Cam Lobe Rise
    Courtesy of GENERAL MOTORS CORP.
3. Using a micrometer, measure the journal diameter.
  Journal Diameter
  1. Standard: 44.399-44.424 mm (1.748-1.749 in.)
  2. Service Limit: 44.375 mm (1.747 in.) min.
    
    Fig 7: Using A Micrometer, Measure The Journal Diameter
    Courtesy of GENERAL MOTORS CORP.
4. Using an inside micrometer or Gauge Ball Set SA91102NE (or equivalent), measure the housing bore diameter.
  Bore Diameter
  1. Standard: 44.475-44.500 mm (1.751-1.752 in.)
  2. Service Limit: 44.513 mm (1.753 in.) max.
    
    Fig 8: Measuring The Housing Bore Diameter
    Courtesy of GENERAL MOTORS CORP.
5. Subtract the journal diameter measurement from the housing bore diameter measurement. If the clearance is greater than maximum, replace the camshaft and/or cylinder head.
  Oil Clearance
  1. Standard: 0.51-0.101 mm (0.0020-0.0040 in.)
  2. Service Limit: 0.138 mm (0.0054 in.) max.
6. Inspect camshaft bore for flatness. Using a precision Straight Edge (24") SA9177NE (or equivalent) and Feeler Gauge SA91101NE (or equivalent), measure the surfaces contacting the camshaft for warpage. If warpage is greater than maximum, replace the cylinder head.
  Maximum Warpage
  1. Standard: 0.05 mm (0.0020 in.) max.
  2. Service Limit: 0.064 mm (0.0025 in.) max.
    
    Fig 9: Inspecting Camshaft Bore For Flatness
    Courtesy of GENERAL MOTORS CORP.