GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Camshaft and Bearings

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REMOVAL & INSTALLATION



Most engines covered by this manual (except the 1.9L) utilize lifters between the camshaft and valve train. 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.

1.9L Engine

See Figures 1 and 2

  1. Remove the rocker (camshaft) cover from the engine. For details, please refer to the procedure earlier in this section.
  2.  
  3. Rotate camshaft until No. 4 cylinder is on the TDC of it's compression stroke.
  4.  
  5. Remove the distributor cap. Using a marking tool, mark the rotor-to-housing and the housing-to-engine positions, then remove the distributor from the engine.
  6.  
  7. Disconnect the fuel lines and remove the fuel pump from the engine.
  8.  
  9. Using two pry bars, depress the timing chain adjuster lock lever to lock the automatic adjuster shoe in its fully retracted position. After locking the automatic adjuster, check that the chain is in a free state.
  10.  



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Fig. Fig. 1: Depressing the adjuster and adjuster lock lever-1.9L engine



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Fig. Fig. 2: Locking the timing chain adjuster in position-1.9L engine

  1. Remove the timing sprocket-to-camshaft bolt, the sprocket and the fuel pump drive cam from the camshaft. Keep the timing sprocket on the chain damper and the tensioner without removing the chain from the sprocket.
  2.  
  3. Remove rocker arm, the shaft and the bracket assembly, the remove the camshaft assembly.
  4.  

To install:
  1. Using set of "V'' blocks and a dial indicator, inspect the camshaft for damage and/or wear; replace it, if necessary.
  2.  
  3. Using a generous amount of clean engine oil or a suitable pre-lube, lubricate the camshaft and journals.
  4.  
  5. Install the camshaft, the rocker arm, the shaft and the bracket assembly.
  6.  
  7. Check that the mark on the No. 1 rocker arm shaft bracket is in alignment with the mark on the camshaft and that the crankshaft pulley groove is aligned with the TDC mark (0 degree) on the front cover.
  8.  
  9. Assemble the timing sprocket to the camshaft by aligning it with the pin on the camshaft; use care not to remove the chain from the sprocket.
  10.  
  11. Install the fuel pump drive cam, the sprocket retaining bolt and washer. Remove the half-moon seal in from end of head; then install torque wrench and torque bolt to 58 ft. lbs. (78 Nm); replace the half-moon seal in cylinder head.
  12.  
  13. Using the alignment marks, install the distributor.
  14.  
  15. Using a medium pry bar, depressing the adjuster shoe to release the lock, check the timing chain tension.
  16.  
  17. Check valve timing, the rotor and mark on distributor housing should be in alignment when the No. 4 cylinder on TDC. The timing mark on damper pulley should align with TDC mark (0 degree mark) on front cover.
  18.  
  19. To complete the installation, install the rocker arm cover and components. Adjust the drive belts. Refill the cooling system.
  20.  

2.0L Engine

See Figure 3

If the camshaft bearings are to be replaced, the following procedure requires the use of the camshaft bearing removal/installation tool No. J-6098 or equivalent.

  1. Drain the engine cooling system.
  2.  
  3. Remove the timing chain and the rocker arm assemblies.
  4.  
  5. Remove the radiator hoses, the radiator-to-engine bolts and the radiator.
  6.  
  7. Remove the distributor cap, mark the rotor-to-housing and the housing-to-engine positions, then remove the distributor.
  8.  
  9. Raise and support the front of the truck safely using jackstands.
  10.  
  11. Disconnect the fuel lines and remove the fuel pump.
  12.  
  13. Remove the jackstands and carefully lower the vehicle.
  14.  
  15. Remove the rocker arm studs and the pushrod guides.
  16.  
  17. Remove the valve lifters.
  18.  

When removing the pushrods and the valve lifters, keep them in order. All valve train components which are to be reused MUST be reinstalled in their original locations.

  1. Carefully pull the camshaft from the front of the block, being sure that the camshaft lobes do not contact the bearings.
  2.  



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Fig. Fig. 3: Timing chain and camshaft mounting-2.0L engine

  1. If removal of camshaft bearings is necessary, use the following procedure:
    1. Using camshaft bearing removal/installation tool J-6098 or equivalent, install the 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.  

  2.  

To install:
  1. If the camshaft bearings were removed:
    1. Install the rear and intermediate bearings with the oil hole between the 2 and 3 o'clock position. Install the front bearing with the holes at 11 o'clock and 2 o'clock.
    2.  
    3. Install a fresh camshaft bearing rear cover using sealant.
    4.  

  2.  
  3. 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.
  4.  

If installing a new camshaft, be sure to coat the lobes with GM Part No. 1051396 or equivalent.

  1. Install the camshaft sprocket and timing chain. Align the timing chain and sprockets and tighten the camshaft sprocket bolt.
  2.  
  3. Install the remaining components in the reverse order of removal.
  4.  
  5. Adjust the valve lash. Adjust the drive belts. Refill the cooling system.
  6.  

2.2L Diesel Engine

See Figure 4

If the camshaft bearings are to be replaced, the following procedure requires the use of the camshaft bearing removal/installation tool No. J-29764 or equivalent.

  1. Remove the engine from the vehicle and mount it on a workstand.
  2.  
  3. Disconnect the PCV hoses from the rocker arm cover.
  4.  
  5. Remove the rocker arm cover, the rocker arm shaft and the pushrods.
  6.  
  7. Remove the upper timing housing cover. Turn the crankshaft to align the timing marks, then install a holding bolt into the injection pump gear.
  8.  
  9. Remove the crankshaft damper pulley and the lower timing housing cover.
  10.  
  11. Remove the injection pump timing gear flange, the timing belt tension spring and the pulley, then remove the timing belt.
  12.  
  13. Remove the camshaft sprocket, the hub and the camshaft oil seal retainer.
  14.  
  15. Remove the oil pump and the valve lifters.
  16.  
  17. Remove the camshaft from the front of the engine, using care not to damage the camshaft bearings.
  18.  

To install:
  1. Inspect the inner bearing faces for damage. Using an inside micrometer, measure the inside diameter of the camshaft bearings; if bearing clearance is greater than 0.0047 in. (0.12mm), replace the bearing(s).
  2.  
  3. Using the camshaft bearing removal/installation tool No. J-29764 or equivalent, remove the camshaft bearings.
  4.  
  5. Using the same tool, install the replacement bearings into the engine block; be sure to align the oil ports in the bearings with those in the cylinder body.
  6.  



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Fig. Fig. 4: Camshaft oil hole alignment-2.2L diesel engine (others similar)

  1. Install the camshaft to the engine, taking care not to damage the bearings.
  2.  
  3. Install the valve lifters and the oil pump.
  4.  
  5. Install the camshaft sprocket, hub and camshaft oil seal retainer.
  6.  
  7. Install the injection pump timing gear flange, the timing belt tension spring, pulley and the timing belt.
  8.  
  9. Install the lower timing housing cover and the crankshaft pulley.
  10.  
  11. Make sure the holding bolt is removed from the injection pump gear, then install the upper timing housing cover.
  12.  
  13. Install the pushrods and the rocker arm shaft, then install the rocker arm cover.
  14.  
  15. Connect the PCV hoses to the rocker arm cover.
  16.  
  17. Install the to the vehicle.
  18.  

2.5L Engine

See Figures 5, 6 and 7

  1. Disconnect the negative battery cable and drain the engine cooling system.
  2.  
  3. Remove the radiator from the vehicle.
  4.  
  5. If equipped with A/C, disconnect the condenser baffles and the condenser, then raise the condenser and set it aside without disconnecting the refrigerant lines.
  6.  
  7. Remove the grille and filler panel from the front of the vehicle.
  8.  
  9. Remove the timing cover from the engine.
  10.  
  11. Matchmark and remove the distributor.
  12.  
  13. Remove the oil pump drive shaft.
  14.  
  15. Remove the pushrod cover:
    1. Remove the alternator and bracket.
    2.  
    3. Disengage the ignition coil wires, then remove the spark plug wires and bracket from the intake manifold.
    4.  
    5. Remove the fuel pipes and clips from the pushrod cover.
    6.  
    7. Remove the oil pressure gage sender, then remove the wiring harness brackets from the pushrod cover.
    8.  
    9. Unscrew the nuts from the cover attaching studs, reverse 2 of the nuts so the washers face outward and screw them back onto the 2 inner studs.
    10.  
    11. Assemble the 2 remaining nuts to the same 2 inner studs with the washers facing inward, then using a small wrench on the inner nut (on each stud) jam the nuts slightly together.
    12.  
    13. Again using the wrench on the inner stud, unscrew the studs until the cover breaks loose, then remove the nuts from the studs and remove the cover from the engine. Remove the studs from the cover and reinstall them to the engine. Tighten the studs to 88 inch lbs. (10 Nm).
    14.  

  16.  
  17. Remove the rocker arm cover, pushrods and valve lifters from the engine.
  18.  

When removing the pushrods and the valve lifters, be sure to keep them in order for reassembly purposes.

Click image to see an enlarged view

Fig. Fig. 5: Removing the camshaft thrust plate-to-engine screws-2.5L engine



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Fig. Fig. 6: Timing mark alignment-2.5L engine

  1. Position the camshaft gear so access to the thrust plate retainers is possible. Remove the camshaft thrust plate-to-engine bolts.
  2.  
  3. If not done already, align the timing marks, then while supporting the camshaft (to prevent damaging the bearing or lobe surfaces), carefully remove it from the front of the engine.
  4.  

To install:
  1. Inspect the camshaft for scratches, pitting and/or wear on the bearing and lobe surfaces. Check the timing gear teeth for damage.
  2.  
  3. If necessary, replace the camshaft bearings as follows:
    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 at the correct clocking to ensure the oil holes in the block and bearings align.
    8.  
    9. Install a fresh camshaft bearing rear cover using sealant.
    10.  

  4.  



Click image to see an enlarged view

Fig. Fig. 7: Pushrod cover installation-2.5L engine

  1. Lubricate the camshaft using a high viscosity oil with zinc (such as 12345501 or equivalent), then carefully insert the camshaft into the engine while aligning the timing marks.
  2.  
  3. Turn the camshaft as necessary, then install the camshaft thrust plate-to-engine bolts to and tighten to 90 inch lbs. (10 Nm).
  4.  
  5. Install the valve lifters, then install the pushrods and rocker arms to the engine.
  6.  
  7. Using a thin bead of RTV sealant, install the pushrod cover to the engine, then tighten the stud nuts to 106 inch lbs. (12 Nm) starting at the front nut and working toward the rear of the engine. Reposition and secure the remaining components which were removed to access the pushrod cover.
  8.  
  9. Install the oil pump drive shaft.
  10.  
  11. Align and install the distributor.
  12.  
  13. Install the timing cover to the engine.
  14.  
  15. Install the the grille and filler panel to the front of the vehicle.
  16.  
  17. If equipped with A/C, reposition and secure the condenser and condenser baffles.
  18.  
  19. Install the radiator from the vehicle.
  20.  
  21. Connect the negative battery cable, then properly refill the engine cooling system.
  22.  

2.8L and 4.3L Engines

See Figures 8, 9, 10 and 11

  1. Properly relieve the fuel system pressure, then disconnect the negative battery cable.
  2.  
  3. Drain the engine cooling system.
  4.  
  5. Remove the radiator from the vehicle.
  6.  
  7. Remove the rocker arm covers from the engine.
  8.  
  9. Remove the intake manifold assembly.
  10.  
  11. Remove the rocker arms, pushrods and lifters.
  12.  
  13. Remove the crankshaft pulley and hub.
  14.  
  15. Remove the engine front (timing) cover.
  16.  



Click image to see an enlarged view

Fig. Fig. 8: Aligning the timing marks-2.8L engine



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Fig. Fig. 9: Aligning the timing marks-4.3L engine

  1. Align the timing marks on the crankshaft and camshaft sprockets.
  2.  
  3. Remove the camshaft sprocket and timing chain.
  4.  
  5. Remove the thrust plate screws, then remove the thrust plate.
  6.  
  7. 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.
  8.  



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Fig. Fig. 10: Use bolts as a handle to help remove the camshaft



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Fig. Fig. 11: 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 105 inch lbs. (12 Nm).
  4.  
  5. Install the timing chain and camshaft sprocket.
  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 radiator to the vehicle.
  18.  
  19. Connect the negative battery cable and properly refill the engine cooling system.
  20.  

INSPECTION



See Figures 12 and 13

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.



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Fig. Fig. 12: Checking the camshaft for straightness



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Fig. Fig. 13: 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 90° 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, the camshaft must be reground or replace.

 
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