GM Storm/Spectrum 1985-1993 Repair Guide

Valves

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REMOVAL & INSTALLATION



See Figures 1 and 2

  1. Remove the cylinder head.
  2.  
  3. If not done already, remove the intake and exhaust manifolds.
  4.  
  5. For the SOHC engine, remove the rocker arms/shafts assemblies. Remove the camshaft and oil seal.
  6.  

When disassembling valve trains, parts of which are to be reused, make sure to keep all components labeled or arranged for installation in their original locations. Rocker arms and/or lifters (tappets) must be installed against the same contact surfaces from which they were removed. Store lifters with the camshaft side downward to keep their oil from draining.

  1. For the DOHC engine, uniformly remove the camshaft bearing cap fasteners and caps. Begin at the center bearing cap of the exhaust camshaft and work outward, then repeat for the intake camshaft. Remove the camshafts, selective shims and lifters. If necessary a magnet may ease lifter removal.
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  3. Support the head on suitable blocks with the cylinder side facing downward to facilitate valve removal.
  4.  
  5. Using J-8062, or an equivalent valve spring compressor, and for the DOHC engines, J-37979-A, or an equivalent compressor adapter, remove the valve split collars. With the collars removed, carefully release the spring tension, then remove the upper valve seat, valve spring and valve from the cylinder head.
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  7. Place the parts from each valve in a separate container, numbered and identified for the valve and cylinder.
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  9. Remove and discard the valve stem oil seal using an appropriate seal removal tool, a new seal will be used at assembly time.
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  11. Use an electric drill and rotary wire brush to clean the intake and exhaust valve ports, combustion chamber and valve seats. In some cases, the carbon build-up will have to be chipped away. Use a blunt pointed drift for carbon chipping, being extremely careful around valve seat areas.
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  13. Use a valve guide cleaning brush and safe solvent to clean the valve guides.
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  15. Clean the valves with a revolving wire brush. Heavy carbon deposits may be removed with blunt drift.
  16.  

When using a wire brush to remove carbon from the cylinder head or valves, make sure the deposits are actually removed and not just burnished.

  1. Wash and clean all valve springs, retainers etc.., in safe solvent. Remember to keep parts from each valve separate.
  2.  
  3. Check the cylinder head for cracks. Cracks usually start around the exhaust valve seat because it is the hottest part of the combustion chamber. If a crack is suspected but cannot be detected visually, have the area checked by pressure testing, with a dye penetrant or other method by an automotive machine shop.
  4.  
  5. Inspect the valves, guides, springs and seats and machine or replace parts, as necessary.
  6.  

To install:
  1. Install new valve seals using the seal removal/installation tool. Do not oil the seal's inner diameter where it contacts the guide.
  2.  
  3. Dip each valve in clean engine oil and install in its original location.
  4.  
  5. Install the valve springs and upper valve seats. Then, using the removal/installation tool to compress the springs, install the valve split collars to the valves. Be careful not to depress the spring cap too far as it may cause seal and stem damage.
  6.  

Once the split collars are installed and the compressor tool is removed, the valve stems should be tapped lightly several times to ensure that the collars are fully seated.

  1. For the DOHC engine, lubricate and install the lifters, camshafts and camshaft bearing caps in their proper locations.
  2.  
  3. For the SOHC engine, lubricate and install the camshaft. Oil and install the lifters and shims, then install the rocker arm/shaft assemblies into their original locations.
  4.  
  5. Install the intake and exhaust manifolds to the cylinder head, unless the cylinder head installation procedure includes these components.
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  7. Install the cylinder head to the vehicle.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Remove the split collars using a suitable valve spring compressor tool to remove spring pressure from the top of the valve stem



Click image to see an enlarged view

Fig. Fig. 2: On DOHC engines, most valve spring compressor tools will also require an adapter

INSPECTION



See Figures 3 and 4

  1. Remove the valves from the cylinder head. Clean the valves, valve guides, valve seats and related components, as explained earlier.
  2.  
  3. Visually check the valves for obvious wear or damage. A burnt valve will have discoloration, severe galling or pitting and even cracks on one area of the valve face. Minor pits, grooves, etc.. can be removed by refacing, but a valve with a cupped head must be replaced. Check the valve stems bends and for obvious wear that is indicated by a step between the part of the stem that travels in the valve guide and the part of the stem near the keeper grooves.
  4.  
  5. Check the valve stem-to-guide clearance in one or more of the following manners, but do not rely on the visual inspection alone:
    1. A visual inspection can give you a fairly good idea if the guide, valve stem or both are worn. Insert the valve into the guide until the valve head is slightly away from the valve seat. Wiggle the valve sideways. A small amount of wobble is normal, excessive wobble means a worn guide and/or valve stem.
    2.  
    3. If a dial indicator is on hand, mount the indicator so that gauge stem is 90 degrees to the valve stem as close to the top of the valve guide as possible. Move the valve from the seat, and measure the valve guide-to-stem clearance by rocking the stem back and forth to actuate the dial indicator. Measure the valve stem using a micrometer and compare to specifications to determine whether stem or guide is causing excessive clearance.
    4.  
    5. If both a ball gauge (small hole gauge) and a micrometer are available. First, measure and note the inside diameter of the valve guide bushing at three locations using the ball gauge. Second, use the micrometer to measure the stem diameter. The stem must not be smaller than 0.274 in. (6.957mm) for the Spectrum 1.5L engine or 0.2335 in. (5.9mm) for 1.6L Storm engines and 0.232 in. (5.9mm) for 1.8L Storm engines. Finally, subtract the valve stem diameter from the corresponding valve guide inside diameter to arrive at the valve clearance.
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    7. On all engines, if clearance is less than 0.0009 in. (0.023mm) for intake valves or 0.0012 in. (0.030mm) for exhaust valves, the valve guide may be reamed.
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    9. On the Spectrum, if the clearance is greater than 0.0022 in. (0.056mm) for intake valves or 0.0025 in. (0.063mm) for exhaust valves, the valve and guide must be replaced.
    10.  
    11. On the Storm, if the clearance is greater than 0.0080 in. (0.20mm) for intake or exhaust valves, the valve and guide must be replaced.
    12.  

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  7. The valve guide, if worn, must be repaired before the valve seats can be resurfaced. A new valve guide should be installed or, in some cases, knurled. Consult the automotive machine shop.
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  9. If the valve guide is okay, measure the valve seat concentricity using a run-out gauge. Follow the manufacturers instructions. If run-out is excessive, reface or replace the valve and machine or replace the valve seat.
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  11. Valves and seats must always be machined together. Never use a refaced valve on a valve seat that has not been machined; never use a valve that has not been refaced on a machined valve seat.
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Click image to see an enlarged view

Fig. Fig. 3: Checking valve stem diameter using a micrometer



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Fig. Fig. 4: Check the stem diameter at 3 points along the valve stem

REFACING



See Figures 5 and 6

  1. Determine if the valve is usable as explained in the Inspection procedure.
  2.  
  3. The correct valve grinding angle is 45.0 degrees for the Spectrum engine or 45.5 degrees for the Storm engines. Make sure the valve refacer grinding wheels are properly dressed.
  4.  
  5. Reface the valve face only enough to remove the pits and grooves or correct any run-out. If the edge or head margin thickness of the valve head is less than 0.0315 in. (0.8mm) thick after grinding, replace the valve, as the valve will run too hot in the engine.
  6.  
  7. Remove all grooves or score marks from the end of the valve stem, and chamfer it, as necessary. But be careful not to remove too much from the overall length of the valve.
  8.  



Click image to see an enlarged view

Fig. Fig. 5: Valve face angle - Spectrum



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Fig. Fig. 6: If the valve margin (head thickness) is less than 0.0315 in. (0.8mm), the valve must be replaced or it will run too hot

 
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