GM Caprice 1990-1993 Repair Guide

Cylinder Head

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See Figures 1, 2 and 3



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Fig. Fig. 1: Cylinder head tightening sequence - 4.3L engine



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Fig. Fig. 2: Cylinder head tightening sequence - 5.0L (VIN Y) engine



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Fig. Fig. 3: Cylinder head tightening sequence - 5.0L (VIN E) and 5.7L engines

REMOVAL AND INSTALLATION



When servicing the engine, be absolutely sure to mark vacuum hoses and wiring so that these items may be properly reconnected during installation. Also, when disconnecting fittings of metal lines (fuel, power brake vacuum), always use two flare nut (or line) wrenches. Hold the wrench on the large fitting with pressure on the wrench as if you were tightening the fitting (clockwise), THEN loosen and disconnect the smaller fitting from the larger fitting. If this is not done, damage (twisting) to the line will result.


CAUTION
Properly relieve the fuel system pressure before disconnecting any lines.

  1. Relieve the fuel system pressure and disconnect negative battery cable.
  2.  
  3. Drain cooling system into a suitable container, loosen and remove belt(s).
  4.  
  5. Remove the intake manifold.
  6.  
  7. Remove the exhaust manifold.
  8.  
  9. Remove the diverter valve, if equipped. If removing the left cylinder head on the 4.3L engine, remove the oil level indicator and guide tube.
  10.  
  11. Disconnect the power steering pump, generator, and/or air conditioning brackets, as necessary, and position aside.
  12.  
  13. Remove the rocker arm cover or valve cover.
  14.  
  15. Tag and disconnect spark plug wires from the spark plugs. Disconnect ground strap and/or negative battery cable from cylinder head as applicable.
  16.  
  17. Loosen cylinder head bolts gradually and in 3 passes.
  18.  
  19. Clean dirt from cylinder head and adjacent area to avoid getting dirt into engine.
  20.  
  21. If necessary, remove rocker arm assemblies and lift out pushrods.
  22.  
  23. Remove cylinder head.
  24.  

To install:
  1. Cylinder heads using a steel gasket should have both sides of the new gasket coated with a good sealer. The coating should be thin and even. Do not use sealer on composite type gaskets.
  2.  
  3. Place gasket over dowel pins.
  4.  
  5. Place cylinder head over dowel pins and gasket.
  6.  
  7. Coat the threads of the cylinder head bolts with sealing compound, part 1052080 or equivalent for all engines except 5.0L (VIN Y) engine. For the 5.0L (VIN Y) engine, dip the bolts in clean engine oil. Insert bolts finger-tight.
  8.  
  9. Following the proper torque sequence, tighten the cylinder head bolts, in 3 passes, to 68 ft. lbs. (92 Nm) for the 5.0L (VIN E) and 5.7L engines or to 65 ft. lbs. (88 Nm) for the 4.3L engine. For the 5.0L (VIN Y) engine tighten bolts to 40 ft. lbs. (54 Nm) on the first pass, then in the 2nd pass, tighten bolts 1-7 and 9 and additional 120 degrees. Finally, in a third pass, tighten bolts 8 and 10 an additional 95 degrees.
  10.  
  11. If removed, position pushrods and attach rocker arm assemblies. Adjust the valves.
  12.  
  13. Connect spark plug wires, and the body ground strap.
  14.  
  15. Attach rocker arm cover or valve cover.
  16.  
  17. Attach power steering pump, generator and/or air conditioning brackets if removed. Install the diverter valve, the oil level indicator and tube, if removed.
  18.  
  19. Attach the intake and exhaust manifolds.
  20.  
  21. Attach both ends of the negative battery to cylinder head cable.
  22.  
  23. Attach fuel filler cap, add coolant and inspect the engine for fluid leakage.
  24.  
  25. Change the engine oil and filter.
  26.  
  27. Start the engine and set the idle and timing to specification.
  28.  

CLEANING AND INSPECTION



See Figure 4



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Fig. Fig. 4: Removing carbon from the cylinder head chamber

Chip carbon away from the valve heads, combustion chambers, and ports, using a chisel made of hardwood. Remove the remaining deposits with a stiff wire brush.

Be sure that the deposits are actually removed, rather than burnished.

Have the cast iron cylinder heads hot-tanked to remove grease, corrosion, and scale from the water passages. Clean the remaining cylinder head parts in an engine cleaning solvent. Do not remove the protective coating from the springs.

Place a straightedge across the gasket surface of the cylinder head. Using feeler gauges, determine the clearance at the center of the straightedge. If warpage exceeds 0.003inch in a 6inch span, or 0.006inch over the total length, the cylinder head must be resurfaced.

If warpage exceeds the manufacturer's maximum tolerance for material removal, the cylinder head must be replaced.When milling the cylinder heads, the intake manifold mounting position is altered, and must be corrected by milling the manifold flange a proportionate amount.

RESURFACING



See Figure 5



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Fig. Fig. 5: Checking the cylinder head for warpage

This procedure should only be performed by a machine shop.

When the cylinder head is removed, check the flatness of the cylinder head gasket surfaces.

  1. Place a straightedge across the gasket surface of the cylinder head. Using feeler gauges, determine the clearance at the center of the straightedge.
  2.  
  3. If warpage exceeds 0.003inch (0.076mm) in a 6inch (152mm) span, or 0.006inch (0.152mm) over the total length, the cylinder head must be resurfaced.
  4.  
  5. If it is necessary to refinish the cylinder head gasket surface, do not plane or grind off more than 0.254mm (0.010inch) from the original gasket surface.
  6.  

When milling the cylinder heads, the intake manifold mounting position is altered, and must be corrected by milling the manifold flange a proportionate amount. Consult an experienced machinist about this.

 
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