GM Full-Size Trucks 1970-1979 Repair Guide

Timing Chain Cover and Front Oil Seal

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REMOVAL & INSTALLATION



Inline 6-Cylinder Engines

See Figures 1 and 2



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Fig. Fig. 1: Apply a suitable sealer to the front cover mounting locations - 250 inline 6-cylinder engine shown



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Fig. Fig. 2: Cut the oil pan seal flush with the front of the block

  1. Drain the engine coolant, remove the radiator hoses, and remove the radiator.
  2.  


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. Remove the fan belt and any accessory belts. Remove the fan pulley.
  2.  
  3. A harmonic balancer/torsional damper puller is necessary to pull the balancer. Install the puller and remove the balancer/damper.
  4.  
  5. Remove the two screws which attach the oil pan to the front cover. Remove the screws which attach the front cover to the block. Do not remove the cover yet.
  6.  
  7. Before the front cover is removed, it is necessary to cut the oil pan front seal. Pull the cover forward slightly.
  8.  
  9. Using a sharp knife or razor knife, cut the oil pan front seal flush with the cylinder block on both sides of the cover.
  10.  
  11. Remove the front cover and the attached portion of oil pan front seal. Remove the front cover gasket from the block.
  12.  
  13. To install the front cover, first obtain an oil pan front seal. Cut the tabs from the new seal.
  14.  
  15. Install the seal in the front cover, pressing the tips into the holes provided in the cover. Coat the mating area of the front cover with a room temperature vulcanizing (RTV) sealer first.
  16.  
  17. Coat the new front cover gasket with sealer and install it on the cover.
  18.  
  19. Apply a 1 / 8 in. bead of RTV sealer to the joint formed at the oil pan and cylinder block.
  20.  
  21. Install the front cover.
  22.  
  23. Install the harmonic balancer. Make sure the front cover seal is positioned evenly around the balancer. If you do not have access to a balancer installation tool (and you probably don't) you can either fabricate one using the illustration as a guide, or you can tap the balancer on using a brass or plastic mallet. If you use the last method, make sure the balancer goes on evenly.
  24.  
  25. The rest of the installation is in the reverse order of removal.
  26.  

V6 and V8 Engines
EXCEPT DIESEL ENGINES

See Figures 3 through 13



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Fig. Fig. 3: Unfasten and remove the retaining bolts ...



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Fig. Fig. 4: ... then remove the pulley



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Fig. Fig. 5: Attach a suitable puller to the torsional damper ...



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Fig. Fig. 6: ... then remove the damper from the crankshaft



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Fig. Fig. 7: Unfasten the front timing cover retaining bolts



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Fig. Fig. 8: Carefully separate the cover from the block



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Fig. Fig. 9: Remove the front cover from the engine block



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Fig. Fig. 10: Carefully clean the old gasket and sealant from the mating surfaces, using a suitable scraper



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Fig. Fig. 11: Sealer application points - gasoline V6 and V8 engines



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Fig. Fig. 12: When guiding the front cover into place, make sure the seal remains in place



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Fig. Fig. 13: View of the seal installation with the cover installed

  1. Drain the cooling system.
  2.  


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. Remove the crankshaft pulley and damper, using Tool J-23523 Damper Pulley remover and installer.
  2.  
  3. Remove the water pump.
  4.  
  5. Unfasten the screws holding the timing case cover to the block, then remove the cover and gaskets.
  6.  
  7. Thoroughly clean the gasket mating surfaces.
  8.  
  9. Use a suitable tool to pry the old seal out of the front face of the cover.
  10.  
  11. Install the new seal so that the open end is toward the inside of the cover, using Tool J-35468 Seal installer.
  12.  

Coat the lip of the new seal with oil prior to installation.

  1. Check that the timing chain oil slinger is in place against the crankshaft sprocket.
  2.  
  3. Apply sealer to the front cover as shown in the accompanying illustration. Install the cover carefully onto the locating dowels.
  4.  
  5. Tighten the attaching screws to 6-8 ft. lbs. (8-11 Nm).
  6.  
  7. Install the damper pulley using Tool J-23523 Damper Pulley installer and tighten the retaining bolt to specifications. (See the Torque Specifications Chart).
  8.  

DIESEL ENGINES

See Figures 14 and 15



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Fig. Fig. 14: Grind a chamfer on one end of each dowel pin - 350 diesel engine



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Fig. Fig. 15: Carefully trim the pan seal using a razor blade

  1. Drain the cooling system and disconnect the radiator hoses.
  2.  


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. Remove all belts, fan and pulley, crankshaft pulley and balancer, using a balancer puller.
  2.  


WARNING
The use of any other type of puller, such as a universal claw type which pulls on the outside of the hub, can destroy the balancer. The outside ring of the balancer is bonded in rubber to the hub. Pulling on the outside will break the bond. The timing mark is on the outside ring. If it is suspected that the bond is broken, check that the center of the keyway is 16 degrees from the center of the timing slot. In addition, there are chiseled aligning marks between the weight and the hub.

  1. Unbolt and remove the cover, timing indicator and water pump.
  2.  
  3. It may be necessary to grind a flat on the cover for gripping purposes.
  4.  
  5. Grind a chamfer on one end of each dowel pin.
  6.  
  7. Cut the excess material from the front end of the oil pan gasket on each side of the block.
  8.  
  9. Clean the block, oil pan and front cover mating surfaces with solvent.
  10.  
  11. Trim about 1 / 8 in. off each end of a new front pan seal.
  12.  
  13. Install a new front cover gasket on the block and a new seal in the front cover.
  14.  
  15. Apply sealer to the gasket around the coolant holes.
  16.  
  17. Apply sealer to the block at the junction of the pan and front cover.
  18.  
  19. Place the cover on the block and press down to compress the seal. Rotate the cover left and right and guide the pan seal into the cavity using a small screwdriver. Oil the bolt threads and install two bolts to hold the cover in place. Install both dowel pins (chamfered end first), then install the remaining front cover bolts.
  20.  
  21. Apply a lubricant, compatible with rubber, on the balancer seal surface.
  22.  
  23. Install the balancer and bolt. Tighten the bolt to 200-300 ft. lbs. (271-406 Nm).
  24.  
  25. Install the other parts in the reverse order of removal.
  26.  

 
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