GM Full Size Vans 1967-1986 Repair Guide

Cylinder Head

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REMOVAL & INSTALLATION



Inline Six Cylinder Engine

See Figure 1



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Fig. Fig. 1: Inline six cylinder engine cylinder head tightening sequence

  1. Drain the cooling system and remove the air cleaner. Disconnect the PCV hose. If equipped, disconnect the air injection hose.
  2.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by 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 accelerator pedal rod at the bellcrank on the manifold, and the fuel and vacuum lines at the carburetor.
  2.  
  3. Disconnect the exhaust pipe at the manifold flange, then remove the manifold bolts and clamps and remove the manifolds and carburetor as an assembly. On those 1975 and later engines with the intake manifold integral with the head, remove the carburetor and the exhaust manifold.
  4.  
  5. Remove the fuel and vacuum line retaining clip from the water outlet. Then disconnect the wire harness from the heat sending unit and coil, leaving the harness clear of clips on the rocker arm cover.
  6.  
  7. Disconnect the radiator hose at the water outlet housing and the battery ground strap at the cylinder head.
  8.  
  9. Disconnect the wires and remove the spark plugs. Disconnect the coil-to-distributor primary wire lead at the coil and remove the coil on models without HEI.
  10.  
  11. Remove the rocker arm cover. Back off the rocker arm nuts, pivot the rocker arms to clear the pushrods and remove the pushrods.
  12.  
  13. Remove the cylinder head bolts, cylinder head and gasket.
  14.  

To install:
  1. Place a new cylinder head gasket over the dowel pins in the cylinder block with the bed up. Do not use sealer on composition steel/asbestos gaskets.
  2.  
  3. Guide and lower the cylinder head into place over the dowels and gasket.
  4.  
  5. Use sealant on the cylinder head bolts, install and tighten them down slightly.
  6.  
  7. Tighten the cylinder head bolts a little at a time with a torque wrench in the correct sequence. Final torque should be as specified.
  8.  
  9. Install the valve pushrods down through the cylinder head openings and seat them in their lifter sockets.
  10.  
  11. Install the rocker arms, balls and nuts and tighten the rocker arm nuts until all pushrod play is taken up.
  12.  
  13. Install the thermostat, the thermostat housing and the water outlet using new gaskets. Then connect the radiator hose.
  14.  
  15. Install the temperature sending switch.
  16.  
  17. Install the spark plugs.
  18.  
  19. Use new plug gaskets (if required) and torque to specifications.
  20.  
  21. Install the coil then connect the heat sending unit and the coil primary wires, and the battery ground cable at the cylinder head.
  22.  
  23. Clean the surfaces and install a new gasket over the manifold studs. Install the manifold. Install the bolts and clamps and torque as specified.
  24.  
  25. Connect the throttle linkage.
  26.  
  27. Connect the PCV fuel and vacuum lines and secure the lines in the clip at the water outlet. Connect the air injection line.
  28.  
  29. Fill the cooling system and check for leaks.
  30.  
  31. Adjust the valve lash as explained later.
  32.  
  33. Install the rocker arm cover and position the wiring harness in the clips.
  34.  
  35. Clean and install the air cleaner.
  36.  

V6 Engines

See Figure 2



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Fig. Fig. 2: V6 engine cylinder head tightening sequence

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the intake manifold as described later.
  6.  
  7. Remove the exhaust manifold as describer later.
  8.  
  9. Remove the air pipe at the rear of the head (right cylinder head).
  10.  
  11. Remove the generator mounting bolt at the cylinder head (right cylinder head).
  12.  
  13. Remove the power steering pump and brackets from the cylinder head, and lay them aside (left cylinder head).
  14.  
  15. Remove the air conditioner compressor, and lay it aside (left cylinder head).
  16.  
  17. Remove the rocker arm cover as outlined previously.
  18.  
  19. Remove the spark plugs.
  20.  
  21. Remove the pushrods, as outlined previously.
  22.  
  23. Remove the cylinder head bolts.
  24.  
  25. Remove the cylinder head.
  26.  
  27. Clean all gasket mating surfaces, install a new gasket and reinstall the cylinder head.
  28.  
  29. Install the cylinder heads using new gaskets. Install the gaskets with the head up.
  30.  

Coat a steel gasket on both sides with sealer. If a composition gasket is used, do not use sealer.

  1. Clean the bolts, apply sealer to the threads, and install them hand tight.
  2.  
  3. Tighten the head bolts a little at a time in the sequence shown. Head bolt torque is listed in the Torque Specifications chart.
  4.  
  5. Install the intake and exhaust manifolds.
  6.  
  7. Torque the cylinder head bolts to 65 ft. lbs. (88 Nm) and adjust the rocker arms.
  8.  
  9. Install the remaining components in the reverse of the removal procedure.
  10.  

Gasoline V8 Engines

See Figures 3 through 7



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Fig. Fig. 3: Use a breaker bar to remove the cylinder head bolts



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Fig. Fig. 4: Remove the cylinder head ...



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Fig. Fig. 5: ... then remove the cylinder head gasket



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Fig. Fig. 6: V8 engine cylinder head tightening sequence



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Fig. Fig. 7: Always use a torque wrench to tighten the bolts to the proper specification

  1. Remove the intake manifold as described later.
  2.  
  3. Remove the exhaust manifolds as described later and tie out of the way.
  4.  
  5. If the van is equipped with air conditioning, remove the A/C compressor and the forward mounting bracket and lay the compressor aside. Do not disconnect any of the refrigerant lines.
  6.  
  7. Back off the rocker arm nuts and pivot the rocker arms out of the way so that the pushrods can be removed. Identify the pushrods so that they can be installed in their original positions.
  8.  
  9. Remove the cylinder head bolts and remove the heads.
  10.  
  11. Install the cylinder heads using new gaskets. Install the gaskets with the head up.
  12.  

Coat a steel gasket on both sides with sealer. If a composition gasket is used, do not use sealer.

  1. Clean the bolts, apply sealer to the threads, and install them hand tight.
  2.  
  3. Tighten the head bolts a little at a time in the sequence shown. Head bolt torque is listed in the Torque Specifications chart.
  4.  
  5. Install the intake and exhaust manifolds.
  6.  
  7. Adjust the rocker arms as explained later.
  8.  

Diesel Engines

See Figures 8 and 9



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Fig. Fig. 8: Exploded view of the 6.2L diesel cylinder head mounting



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Fig. Fig. 9: Tightening sequence for 6.2L diesel engines

  1. Remove the intake manifold, using the procedure outlined above.
  2.  
  3. Remove the rocker arm cover(s), after removing any accessory brackets which interfere with cover removal.
  4.  
  5. Disconnect and label the glow plug wiring.
  6.  
  7. If the right cylinder head is being removed, remove the ground strap from the head.
  8.  
  9. On the 350, remove the rocker arms bolts, the bridged pivots, the rocker arms, and the pushrods, keeping all the parts in order so that they can be returned to their original positions. On the 379, remove the rocker shaft assemblies. It is a good practice to number or mark the parts to avoid interchanging them.
  10.  
  11. Remove the fuel return lines from the nozzles.
  12.  
  13. Remove the exhaust manifold(s), using the procedure outlined earlier in this section.
  14.  
  15. On the 350, remove the engine block drain plug on the side of the engine from which the cylinder head is being removed.
  16.  
  17. Remove the head bolts. Remove the cylinder head.
  18.  
  19. To install, first clean the mating surfaces thoroughly. Install new head gaskets on the engine block. Do not coat the gaskets with any sealer on either engine. The gaskets have a special coating that eliminates the need for sealer. The use of sealer will interfere with this coating and cause leaks. Install the cylinder head onto the block.
  20.  
  21. Clean the head bolts thoroughly. On the 350, dip the bolts in clean engine oil and install them into the cylinder block until the heads of the bolts lightly contact the cylinder head. On the 379, the left rear head bolt must be installed into the head prior to head installation. Coat the threads of the 379 cylinder head bolts with sealing compound (GM part #1052080 or equivalent) before installation.
  22.  
  23. On the 350, tighten the bolts in the illustrated sequence to 100 ft. lbs. (135 Nm). When all the bolts have been tightened to this figure, begin the tightening sequence again, and torque each bolt gradually in the sequence shown until the final torque specified is met.
  24.  
  25. Install the engine block drain plugs on the 350, the exhaust manifolds, the fuel return lines, the glow plug wiring, and the ground strap for the right cylinder head.
  26.  
  27. Install the valve train assembly. Refer to the Diesel Engine Rocker Arm Replacement in this section for the valve lifter bleeding procedures.
  28.  
  29. Install the intake manifold.
  30.  
  31. Install the valve covers. These are sealed with RTV type silicone sealer instead of a gasket. See the Valve Cover procedure for proper sealer application. Install the cover to the head within 10 minutes, while the sealer is still wet.
  32.  

CLEANING & INSPECTION



See Figures 10 and 11



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Fig. Fig. 10: Use a gasket scraper to remove the bulk of the old head gasket from the mating surface



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Fig. Fig. 11: An electric drill equipped with a wire wheel will expedite complete gasket removal

Gasoline Engines

Any diesel cylinder head work should be handled by a reputable machine shop familiar with diesel engines. Disassembly, valve lapping, and assembly can be completed by the following procedures.

One the complete valve train has been removed from the cylinder head(s), the head itself can be inspected, cleaned and machined (if necessary). Set the head(s) on a clean work space, so the combustion chambers are facing up. Begin cleaning the chambers and ports with a hardwood chisel or other non-metallic tool (to avoid nicking or gouging the chamber, ports, and especially the valve seats). Chip away the major carbon deposits, then remove the remainder of carbon with a wire brush fitted to an electric drill.

Be sure that the carbon is actually removed, rather than just burnished.

After decarbonizing is completed, take the head(s) to a machine shop and have the head hot tanked. In this process, the head is lowered into a hot chemical bath that very effectively cleans all grease, corrosion, and scale from all internal and external head surfaces. Also have the machinist check the valve seats and recut them if necessary. When you bring the clean head(s) home, place them on a clean surface. Completely clean the entire valve train with solvent.

CHECKING FOR HEAD WARPAGE



See Figures 12 and 13



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Fig. Fig. 12: Check the cylinder head for warpage along the center using a straightedge and a feeler gauge



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Fig. Fig. 13: Be sure to check for warpage across the cylinder head at both diagonals

Lay the head down with the combustion chambers facing up. Place a straight edge across the gasket surface of the head, both diagonally and straight across the center. Using a flat feeler gauge, determine the clearance at the center of the straight edge. If warpage exceeds 0.003 in. (0.0762mm) in a 6 in. (152mm) span, or 0.006 in. (0.152mm) over the total length, the cylinder head must be resurfaced (which is akin to planing a piece of wood). Resurfacing can be performed at most machine shops.

When resurfacing the cylinder head(s) of V type engines, the intake manifold mounting position is altered, and must be corrected by machining a proportionate amount from the intake manifold flange.

RESURFACING

Cylinder head resurfacing should be done by a qualified machine shop.

 
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