GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Camshaft and Bearings

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REMOVAL & INSTALLATION



On all engines equipped with lifters, a complete new set of lifters must be installed whenever the camshaft is replaced in order to prolong the new camshaft's service life.

2.2L Engine

See Figure 1


CAUTION
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. If equipped, have the air conditioning system discharged by a qualified technician using a proper refrigerant recovery/recycling station.
  2.  
  3. Properly relieve the fuel system pressure, then disconnect the negative battery cable.
  4.  
  5. Drain the engine cooling system and the engine oil.
  6.  
  7. Remove the air duct from the air inlet.
  8.  
  9. Remove the upper radiator shroud, then disengage the oil and transmission cooler lines at the radiator.
  10.  
  11. Tag and disengage all hoses from the radiator.
  12.  
  13. If necessary for clearance, remove the radiator and air conditioning condenser from the vehicle.
  14.  
  15. Remove the serpentine drive belt.
  16.  
  17. Remove the rocker arm cover.
  18.  
  19. Remove the cylinder head.
  20.  
  21. Unfasten the anti-rotation bracket bolts and brackets, then remove the valve lifters.
  22.  
  23. Unfasten the oil pump drive retaining bolt, then remove the drive by lifting and twisting.
  24.  
  25. If equipped, remove the Camshaft Position (CMP) sensor.
  26.  
  27. Remove the crankshaft pulley and hub.
  28.  
  29. Remove the serpentine drive belt idler pulley.
  30.  
  31. Remove the timing cover from the engine.
  32.  
  33. Remove the timing chain and camshaft sprocket.
  34.  
  35. Unfasten the camshaft thrust plate retaining bolts, then remove the plate from the block.
  36.  
  37. Install the sprocket bolts or longer bolts of the same thread into the end of the camshaft as a handle, then pull the camshaft straight out of the engine, turning slightly as it is withdrawn and taking care not to damage the bearings.
  38.  
  39. If removal of camshaft bearings is necessary, use the following procedure:
    1. Install a camshaft bearing removal/installation tool with the shoulder toward the bearing. Ensure that enough threads are engaged.
    2.  
    3. Using two wrenches, hold the puller screw while turning the nut. When the bearing has been released from the bore, remove the tool.
    4.  
    5. Assemble the tool on the driver to remove the front and rear bearings.
    6.  
    7. Install the bearings (outer bearings first) so that the oil holes in the block and the bearing align.
    8.  
    9. Install a fresh camshaft bearing rear cover using sealant.
    10.  

  40.  

To install:


Click image to see an enlarged view

Fig. Fig. 1: A suitable camshaft bearing removal/installation tool is required when replacing the bearings

  1. Inspect the camshaft, journals and lobes for wear and replace, if necessary.
  2.  
  3. Inspect the bearings for scratches, pits or a loose fit in their bores and replace, if necessary.
  4.  
  5. Coat the camshaft lobes and journals with a high viscosity oil with zinc such as No. 12345501, or equivalent.
  6.  
  7. Carefully insert the camshaft in the engine, turning it slightly from side to side and it is inserted.
  8.  
  9. Install the thrust plate and tighten the retaining bolts to 106 inch lbs. (12 Nm).
  10.  
  11. If equipped, install the CMP sensor.
  12.  
  13. Install the timing chain and camshaft sprocket.
  14.  
  15. Install the timing cover to the engine.
  16.  
  17. Install the serpentine drive belt idler pulley.
  18.  
  19. Install the crankshaft pulley and hub.
  20.  
  21. Install the oil pump drive by inserting while twisting, then install the retaining bolt and tighten to 18 ft. lbs. (25 Nm).
  22.  
  23. Install the valve lifters and the anti-rotation brackets.
  24.  
  25. Install the cylinder head.
  26.  
  27. Install the rocker arm cover.
  28.  
  29. Install the air conditioning condenser and the radiator assemblies. Engage all hoses removed from the radiator.
  30.  
  31. Engage the oil and transmission cooler lines at the radiator, then install the radiator shroud.
  32.  
  33. Install the serpentine drive belt.
  34.  
  35. Engage the air cleaner assembly and connect the negative battery cable.
  36.  
  37. Fill the crankcase with the correct grade and amount of oil.
  38.  
  39. Fill the cooling system with coolant.
  40.  
  41. Connect the negative battery cable.
  42.  
  43. Have the air conditioning system charged by a qualified technician using a proper refrigerant recovery/recycling station.
  44.  

4.3L Engines

See Figures 2, 3 and 4


CAUTION
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. If equipped, have the air conditioning system discharged by a qualified technician using a proper refrigerant recovery/recycling station.
  2.  
  3. Properly relieve the fuel system pressure, then disconnect the negative battery cable.
  4.  
  5. Disconnect the air intake duct, if applicable.
  6.  
  7. Drain the engine cooling system.
  8.  
  9. If necessary for clearance, remove the radiator and air conditioning condenser from the vehicle.
  10.  
  11. Remove the rocker arm covers from the engine.
  12.  
  13. Remove the intake manifold assembly.
  14.  
  15. Remove the rocker arms, pushrods and lifters.
  16.  
  17. Remove the crankshaft pulley and hub.
  18.  
  19. Remove the engine front (timing) cover.
  20.  



Click image to see an enlarged view

Fig. Fig. 2: Aligning the timing marks-4.3L engine

  1. Align the timing marks on the crankshaft and camshaft sprockets.
  2.  
  3. Unfasten the balance shaft drive gear bolt and remove the gear to allow clearance for camshaft removal.
  4.  
  5. Remove the camshaft sprocket and timing chain.
  6.  
  7. If necessary, remove the crankshaft position sensor reluctor ring and sprocket.
  8.  
  9. Remove the thrust plate screws, then remove the thrust plate.
  10.  
  11. Install the sprocket bolts or longer bolts of the same thread into the end of the camshaft as a handle, then remove the camshaft front the front of the engine while turning slightly from side to side, as necessary. Take care not to damage the camshaft bearings when removing the camshaft.
  12.  



Click image to see an enlarged view

Fig. Fig. 3: Use bolts as a handle to help remove the camshaft



Click image to see an enlarged view

Fig. Fig. 4: Common camshaft bearing removal tool-OHV engines

  1. If removal of camshaft bearings is necessary, use the following procedure:
    1. Install a camshaft bearing removal/installation tool with the shoulder toward the bearing. Ensure that enough threads are engaged.
    2.  
    3. Using two wrenches, hold the puller screw while turning the nut. When the bearing has been released from the bore, remove the tool.
    4.  
    5. Assemble the tool on the driver to remove the front and rear bearings.
    6.  
    7. Install the bearings so that the oil holes in the block and the bearing align.
    8.  
    9. Install a fresh camshaft bearing rear cover using sealant.
    10.  

  2.  

To install:
  1. Lubricate the camshaft journals with clean engine oil or a suitable pre-lube, then install the camshaft into the block being extremely careful not to contact the bearings with the cam lobes.
  2.  
  3. Install the camshaft thrust plate and tighten the bolts to 106 inch lbs. (12 Nm).
  4.  
  5. Install the timing chain, camshaft sprocket and balance shaft drive gear.
  6.  
  7. Install the engine front (timing) cover.
  8.  
  9. Install the crankshaft pulley and hub.
  10.  
  11. Install the valve lifters, then install the pushrods and rocker arms. Properly adjust the valve clearance.
  12.  
  13. Install the intake manifold assembly.
  14.  
  15. Install the rocker arm covers to the engine.
  16.  
  17. Install the air conditioning condenser and the radiator assemblies. Engage all hoses removed from the radiator.
  18.  
  19. Connect the negative battery cable and properly refill the engine cooling system.
  20.  

INSPECTION



See Figures 5 and 6

Using solvent, degrease the camshaft and clean out all of the oil holes. Visually inspect the cam lobes and bearing journals for excessive wear. If a lobe is questionable, check all of the lobes as indicated. If a journal or lobe is worn, the camshaft MUST BE reground or replaced.



Click image to see an enlarged view

Fig. Fig. 5: Checking the camshaft for straightness



Click image to see an enlarged view

Fig. Fig. 6: Measuring camshaft lobe lift

If a journal is worn, there is a good chance that the bearings are worn and need replacement.

If the lobes and journals appear intact, place the front and rear journals in V-blocks and rest a dial indicator on the center journal. Rotate the camshaft to check the straightness. If deviation exceeds 0.001 in. (0.0254mm), the camshaft should likely be replaced.

On most engines lobe lift can be measured with the camshaft still installed. Simply remove the rocker cover and rocker arm, then use a dial gauge on the end of the pushrod. When the pushrod is at the bottom of its travel, set the dial gauge to "0'' then turn the engine and note the gauge's highest reading.

Check the camshaft lobes with a micrometer, by measuring the across the lobe centerline from the nose to the base and again at the centerline across the diameter at 90º from the first measurement (see illustration). The lobe lift is determined by subtracting the second measurement (diameter) from the first (diameter plug lobe lift). If the lobes vary from specification,