GM Full-Size Trucks 1980-1987 Repair Guide

Camshaft

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REMOVAL & INSTALLATION



In-line 6 Cylinder

See Figure 1

  1. Remove the grille. Remove the radiator hoses and remove the radiator.
  2.  
  3. Remove the timing gear cover.
  4.  
  5. Remove the valve cover and gasket, loosen all the rocket arm nuts, and pivot the rocker arms clear of the pushrods.
  6.  
  7. Remove the distributor and the fuel pump.
  8.  
  9. Remove the pushrods. Remove the coil and then remove the side cover. Remove the valve lifters.
  10.  
  11. Remove the two camshaft thrust plate retaining screws by working through the holes in the camshaft gear.
  12.  
  13. Remove the camshaft and gear assembly by pulling it out through the front of the block.
  14.  
  15. If either the camshaft or the camshaft gear is being renewed, the gear must be pressed off the camshaft. The replacement parts must be assembled in the same way. When placing the gear on the camshaft, press the gear onto the shaft until it bottoms against the gear spacer ring. The end clearance of the thrust plate should be 0.001-0.005 inch.
  16.  
  17. Pre-lube the camshaft lobes with clean engine oil and then install the camshaft assembly in the engine. Be careful not to damage the bearings.
  18.  
  19. Turn the crankshaft and the camshaft gears so that the timing marks align. Push the camshaft into position and install and torque the thrust plate bolts to 7 ft. lbs.
  20.  
  21. Check camshaft and crankshaft gear run-out with a dial indicator. Camshaft gear run-out should not exceed 0.004 inch and crankshaft gear run-out should not be above 0.003 inch.
  22.  
  23. Using a dial indicator, check the backlash at several points between the camshaft and crankshaft gear teeth. Backlash should be 0.004-0.006 inch.
  24.  



Click image to see an enlarged view

Fig. Fig. 1: Removing camshaft. Slowly turn the cam as you remove it

  1. Install the timing gear cover. Install the harmonic balancer.
  2.  
  3. Install the valve lifters and the pushrods. Install the side cover. Install the coil and the fuel pump.
  4.  
  5. Install the distributor and set the timing. Pivot the rocker arms over the pushrods and adjust the valves.
  6.  
  7. Install the radiator, hoses and grille.
  8.  

Gasoline V6 and V8

See Figures 2 and 3

  1. Disconnect the negative battery cable.
  2.  
  3. Drain and remove the radiator.
  4.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Disconnect the fuel line at the fuel pump. Remove the pump.
  2.  
  3. Disconnect the throttle cable and the air cleaner.
  4.  
  5. Remove the alternator belt, loosen the alternator bolts and move the alternator to one side.
  6.  
  7. Remove the power steering pump from its brackets and move it out of the way.
  8.  
  9. It may be necessary on some models, to remove the air conditioning compressor from its brackets and move the compressor out of the way without disconnecting the lines.
  10.  



Click image to see an enlarged view

Fig. Fig. 2: The camshaft timing gear bolts may be grasped and used to pull the camshaft from the engine block



Click image to see an enlarged view

Fig. Fig. 3: Slowly turn the camshaft as you remove it from the engine

  1. Disconnect the hoses from the water pump.
  2.  
  3. Disconnect the electrical and vacuum connections.
  4.  
  5. Mark the distributor as to location in the block. Remove the distributor.
  6.  
  7. Raise the car and drain the oil pan.
  8.  
  9. Remove the exhaust crossover pipe and starter motor.
  10.  
  11. Disconnect the exhaust pipe at the manifold.
  12.  
  13. Remove the harmonic balancer and pulley.
  14.  
  15. Support the engine and remove the front motor mounts.
  16.  
  17. Remove the flywheel inspection cover.
  18.  
  19. Remove the engine oil pan.
  20.  
  21. Support the engine.
  22.  
  23. Remove the engine front cover.
  24.  
  25. Remove the valve covers.
  26.  
  27. Remove the intake manifold, oil filler pipe, and temperature sending switch.
  28.  
  29. Mark or assort the lifters, pushrods, and rocker arms as to location so that they may be installed in the same position. Remove these parts.
  30.  
  31. If the car is equipped with air conditioning, discharge the air conditioning system, see Routine Maintenance , and remove the condenser.
  32.  
  33. Remove the fuel pump eccentric, camshaft gear, oil slinger, and timing chain. Remove the camshaft thrust plate on front of camshaft, if equipped.
  34.  
  35. Carefully remove the camshaft from the engine pulling straight backwards to avoid journal or bearing damage. The camshaft timing gear bolts may be used as a grip to pull the camshaft from the block.
  36.  
  37. Inspect the shaft for signs of excessive wear or damage.
  38.  
  39. Liberally coat camshaft and bearings with heavy engine oil or engine assembly lubricant and insert the cam into the engine.
  40.  
  41. Align the timing marks on the camshaft and crankshaft gears. See Timing Chain Replacement for details.
  42.  
  43. Install the distributor using the locating marks made during removal. If any problems are encountered, see Distributor Installation.
  44.  
  45. Install the remainder of the parts in the reverse of above but pay attention to the following points:
    1. Install the timing indicator before installing the power steering pump bracket.
    2.  
    3. Install the flywheel inspection cover after installing the starter.
    4.  
    5. Replace the engine oil and radiator coolant.
    6.  

  46.  

8-350 Diesel

See Figures 4 and 5

If equipped with air conditioning, the system must be discharged by an air conditioning specialist before the camshaft is removed. The condenser must also be removed from the car. Removal of the camshaft also requires removal of the injection pump drive and driven gears, removal of the intake manifold, disassembly of the valve lifters, and retiming of the injection pump.

  1. Disconnect the negative battery cables.
  2.  
  3. Remove the intake manifold and gasket and the front and rear intake manifold seals. Refer to the intake manifold removal and installation procedure.
  4.  
  5. Remove the balancer pulley and the balancer. Remove the engine front cover.
  6.  
  7. Remove the valve covers. Remove the rocker arms, pushrods and valve lifters. Be sure to keep the parts in order so that they may be returned to their original positions.
  8.  
  9. Remove the camshaft sprocket retaining bolt, and remove the timing chain and sprockets, using the procedure outlined earlier.
  10.  
  11. Position the camshaft dowel pin at the 3 o'clock position.
  12.  
  13. Push the camshaft rearward and hold it there, being careful not to dislodge the oil gallery plug at the rear of the engine. Remove the fuel injection pump drive gear by sliding it from the camshaft while rocking the pump driven gear.
  14.  
  15. To remove the fuel injection pump driven gear, remove the pump adapter, the snapring, and remove the selective washer. Remove the driven gear and spring.
  16.  
  17. Remove the camshaft by sliding it out the front of the engine. Be extremely careful not to allow the cam lobes to contact any of the bearings, or the journals to dislodge the bearings during camshaft removal. Do not force the camshaft, or bearing damage will result.
  18.  
  19. If either the injection pump drive or driven gears are to be replaced, replace both gears.
  20.  
  21. Coat the camshaft and the cam bearings with a heavy weight engine oil, GM lubricant No. 1052365 or the equivalent.
  22.  
  23. Carefully slide the camshaft into position in the engine.
  24.  
  25. Fit the crankshaft and camshaft sprockets, aligning the timing marks as shown in the timing chain removal and installation procedure, above. Remove the sprockets without disturbing the timing.
  26.  
  27. Install the injection pump driven gear, spring, shim, and snapring. Check the gear end-play. If the end-play is not within 0.002-0.015 inch, replace the shim to obtain the specified clearance. Shims are available in 0.003 inch increments, from 0.080 inch to 0.115 inch.
  28.  
  29. Position the camshaft dowel pin at the 3 o'clock position. Align the "zero" marks on the pump drive gear and pump driven gear. Hold the camshaft in the rearward position and slide the pump drive gear onto the camshaft. Install the camshaft bearing retainer.
  30.  
  31. Install the timing chain and sprockets, making sure the timing marks are aligned.
  32.  
  33. Install the lifters, pushrods and rocker arms. See Rocker Arm Replacement, Diesel Engine for lifter bleed down procedures. Failure to bleed down the lifters could bend valves when the engine is turned over.
  34.  
  35. Install the injection pump adapter and injection pump. See the appropriate Sections under Fuel System above for procedures.
  36.  
  37. Install the remaining components in the reverse order of removal
  38.  



Click image to see an enlarged view

Fig. Fig. 4: Camshaft and oil gallery plugs at rear of block



Click image to see an enlarged view

Fig. Fig. 5: 350 diesel injection pump drive gear installation

8-379 Diesel
REMOVAL
  1. Disconnect both batteries.
  2.  
  3. Jack up the truck and safely support it with jackstands.
  4.  
  5. Drain the cooling system, including the block.
  6.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Disconnect the exhaust pipes at the manifolds. Remove the fan shroud.
  2.  
  3. Lower the truck.
  4.  
  5. Remove the radiator and fan.
  6.  
  7. Remove the vacuum pump and the intake manifold.
  8.  
  9. Remove the injection pump and lines as outlined in Fuel System . Make sure you cap all injection lines to prevent dirt from entering the system, and tag the lines for later installation.
  10.  
  11. Remove the water pump.
  12.  
  13. Remove the injection pump drive gear.
  14.  
  15. Scribe a mark aligning the line on the injection pump flange to the front cover.
  16.  
  17. Remove the injection pump from the cover.
  18.  
  19. Remove the power steering pump and the generator and lay them aside.
  20.  
  21. If the truck is equipped with air conditioning, remove the compressor (with the lines attached) and position it out of the way.
  22.  


CAUTION
DO NOT disconnect the air conditioning lines unless you are familiar with this procedure. Refer to Routine Maintenance "Air Conditioning".

  1. Remove the valve covers.
  2.  
  3. Remove the rocker shaft assemblies and pushrods. Place the pushrods in order in a rack (easily by punching holes in a piece of heavy cardboard and numbering the holes) so that they can be installed in correct order.
  4.  
  5. Remove the thermostat housing and the crossover from the cylinder heads.
  6.  
  7. Remove the cylinder heads , with the exhaust manifolds attached.
  8.  
  9. Remove the valve lifter clamps, guide plates and valve lifters. Place these parts in a rack so they can be installed in the correct order.
  10.  
  11. Remove the front cover.
  12.  
  13. Remove the timing chain assembly.
  14.  
  15. Remove the fuel pump.
  16.  
  17. Remove the camshaft retainer plate.
  18.  
  19. If the truck is equipped with air conditioning, remove the air conditioning condenser mounting bolts. Have an assistant help in lifting the condenser out of the way.
  20.  
  21. Remove the camshaft by carefully sliding it out of the block.
  22.  

INSTALLATION

Whenever a new camshaft is installed, GM recommends replacing all the valve lifters, as well as the oil filter. The engine oil must be changed. These measures will help ensure proper wear characteristics of the new camshaft.

  1. Coat the camshaft lobes with Molykote or an equivalent lube. Liberally lube the camshaft journals with clean engine oil and install the camshaft carefully.
  2.  
  3. Install the camshaft retainer plate and torque the bolts to 20 ft. lbs.
  4.  
  5. Install the fuel pump.
  6.  
  7. Install the timing chain assembly.
  8.  
  9. Install the front cover.
  10.  
  11. Install the valve lifters, guide plates and clamps. Rotate the crankshaft as previously outlined so that the lifters are free to travel.
  12.  
  13. Install the cylinder heads.
  14.  
  15. Install the pushrods in their original order. Install the rocker shaft assemblies, then install the valve covers.
  16.  
  17. Install the injection pump to the front cover, making sure the lines on the pump and the scribe line on the front cover are aligned.
  18.  
  19. Install the injection pump driven gear, making sure the gears are aligned. Re-time the injection pump.
  20.  
  21. Install the remaining engine components in the reverse order of removal. Make the necessary adjustments (drive belts, etc.) and refill the cooling system.
  22.  

CAMSHAFT INSPECTION



Completely clean the camshaft with solvent, paying special attention to cleaning the oil holes. Visually inspect the cam lobes and bearing journals for excessive wear. If a lobe is questionable, have the cam checked at a reputable machine shop; if a journal or lobe is worn, the camshaft must be reground or replaced. Also have the camshaft checked for straightness on a dial indicator.

If a cam journal is worn, there is a good chance that the bushings are worn.

 
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