Chevrolet Blazer/Jimmy 1969-1982 Repair Guide

Cylinder Head

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REMOVAL & INSTALLATION



Six Cylinder Engines


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Fig. Fig. 1 Cylinder head bolt tightening sequence-6 cylinder engines

  1. Drain the cooling system and remove the air cleaner. Disconnect the PCV hose. If equipped, disconnect the air injection hose.
  2.  
  3. Disconnect the accelerator pedal rod at the bellcrank on the manifold, and the fuel and vacuum lines at the carburetor.
  4.  
  5. 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 1975 and later engines, remove the carburetor and the exhaust manifold.
  6.  
  7. Remove the fuel and vacuum line retaining clip from the water outlet. Then disconnect the wire harness from the temperature sending unit and coil, leaving the harness clear of clips on the rocker arm cover.
  8.  
  9. Disconnect the radiator hose at the water outlet housing and the battery ground strap at the cylinder head.
  10.  
  11. 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.
  12.  
  13. Remove the rocker arm cover. Back off the rocker arm nuts, pivot the rocker arms to clear the pushrods and remove the pushrods.
  14.  
  15. Remove the cylinder head bolts, cylinder head and gasket.
  16.  

To install:

  1. Place a new cylinder-head gasket over the dowel pins in the cylinder block with the bead 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 snugly.
  6.  
  7. Tighten the cylinder head bolts a little at a time with a torque wrench in the correct sequence to the proper specification.
  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 necessary) and torque to specifications. This is covered in .
  20.  
  21. Install the coil then connect the temperature 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 valves 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.  

V8 Gasoline Engines


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Fig. Fig. 2 Cylinder head bolt tightening sequence-V8 engines



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Fig. Fig. 3 Remove the old gasket material



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Fig. Fig. 4 Loosen the cylinder head retaining bolts ...



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Fig. Fig. 5 ... then remove the cylinder head from the engine



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Fig. Fig. 6 When installing the cylinder head, use a torque wrench and tighten the bolts in the proper sequence

  1. Remove the intake manifold as outlined in this section.
  2.  
  3. Remove the exhaust manifolds as described later and tie out of the way.
  4.  
  5. If the vehicle is equipped with A/C, remove the 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 bead 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 to the proper specification.
  4.  
  5. Install the intake and exhaust manifolds.
  6.  
  7. Install the A/C compressor.
  8.  
  9. Adjust the valves as explained later.
  10.  

Diesel Engine


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Fig. Fig. 7 Cylinder head bolt tightening sequence-V8 diesel engines

  1. Remove the fuel injection lines. Cap all lines, nozzles and fittings.
  2.  
  3. Remove the intake manifold.
  4.  
  5. Remove the rocker arm covers, after removing any accessory brackets that are in the way.
  6.  


CAUTION
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 quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Drain the radiator and remove the dipstick tube.
  2.  
  3. Disconnect the ground wire at the cowl.
  4.  
  5. Raise and support the car, disconnect the exhaust pipe from the manifold and then lower the car.
  6.  
  7. If equipped with AC, remove the compressor and position it out of the way.
  8.  
  9. Remove the alternator.
  10.  
  11. Tag and disconnect the glow plug wires.
  12.  
  13. Remove the rocker arm assemblies and then remove the pushrods. Mark the pushrods for reinstallation. Keep the rocker arms and pushrods in order so they can be installed in the same location.
  14.  
  15. Disconnect the radiator, by-pass and heater hoses.
  16.  
  17. Disconnect the ground strap.
  18.  
  19. Remove the thermostat housing/crossover at the head.
  20.  
  21. Remove the cylinder head bolts (17 on each side). The rear left head bolt may have to remain in the head upon removal.
  22.  
  23. Carefully lift off the cylinder head.
  24.  

To install:

  1. Clean the cylinder head-to-engine block mating surfaces thoroughly. Install new head gaskets on the engine block. Do NOT coat the gaskets with any kind of sealer. The gaskets come with a special coating that eliminates the need for sealer. The use of any additional sealer will interfere with this coating and lead to leakage.
  2.  
  3. Carefully guide the cylinder head into place on the block. The left rear cylinder head bolt must be installed in the head prior to installation.
  4.  
  5. Coat the threads of the head bolts with sealing compound and then install them finger-tight.
  6.  
  7. Tighten each bolt a little at a time in the proper sequence to the correct specification.
  8.  
  9. Installation of the remaining components is in the reverse order. Use RTV silicone sealant when installing the rocker arm covers.
  10.  

CLEANING & INSPECTION



Gasoline Engines


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Fig. Fig. 8 Use a gasket scraper to remove the bulk of the old head gasket from the mating surface



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Fig. Fig. 9 An electric drill equipped with a wire wheel will expedite complete gasket removal



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Fig. Fig. 10 Check the cylinder head for warpage along the center using a straightedge and a feeler gauge



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Fig. Fig. 11 Be sure to check for warpage across the cylinder head at both diagonals

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 following the gasoline engine procedures.

Once 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



Lay the head down with the combustion chambers facing up. Place a straightedge 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 straightedge. If warpage exceeds 0.003- in a 6- span, or 0.006- 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 V8 engines, the intake manifold mounting position is altered, and must be corrected by machining a proportionate amount from the intake manifold flange.

 
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