Mazda Trucks 1972-1986 Repair Guide

Valves and Valve Springs

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REMOVAL & INSTALLATION



1,586cc, 1,796cc, 1,970cc, 1,998cc and 2,209cc Engines

See Figures 1 through 27

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Fig. Fig. 1: Use a valve spring compressor tool to relieve spring tension from the valve caps



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Fig. Fig. 2: A magnet may be helpful in removing the valve keepers



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Fig. Fig. 3: Remove the spring from the valve stem in order to access the seal



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Fig. Fig. 4: Remove the valve stem seal from the cylinder head



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Fig. Fig. 5: Invert the cylinder head and withdraw the valve from the cylinder head bore



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Fig. Fig. 6: A wire wheel may be used to clean the combustion chambers of carbon deposits



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Fig. Fig. 7: A dial gauge may be used to check valve stem-to-guide clearance



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Fig. Fig. 8: Valve stems may be rolled on a flat surface to check for bends



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Fig. Fig. 9: With the valve spring out of the way, the valve stem seals may now be replaced



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Fig. Fig. 10: Use a caliper gauge to check the valve spring free-length



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Fig. Fig. 11: Check the valve spring for squareness on a flat service; a carpenter's square can be used



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Fig. Fig. 12: The valve spring should be straight up and down when placed like this



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Fig. Fig. 13: Use a micrometer to check the valve stem diameter



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Fig. Fig. 14: Check the cylinder head for flatness across the head surface



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Fig. Fig. 15: Checks should be made both straight across the cylinder head and at both diagonals



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Fig. Fig. 16: View of critical valve dimensions



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Fig. Fig. 17: Using a valve grinding machine to re-face an engine valve



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Fig. Fig. 18: Example of a homemade valve lapping tool



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Fig. Fig. 19: Using a hand lapping tool to lap valves



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Fig. Fig. 20: Example of the marks seen on the valve tips for valves with rotators



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Fig. Fig. 21: Testing the valve spring pressure



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Fig. Fig. 22: Measuring valve spring installed heightthe measurement is taken from the spring seat (cylinder head), to the top of the spring (bottom edge of the spring retainer)



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Fig. Fig. 23: Measure the springs' free lengththere should be no more than 5/64 inch (0.078 inches) variation between springs



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Fig. Fig. 24: View of the valve and spring componentsnot shown are the valve keepers, which sit in the center of the retainer and lock around the valve



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Fig. Fig. 25: View of a typical valve sealbe sure to push the new seal firmly over the valve guide



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Fig. Fig. 26: Using a valve guide driver to install a new valve guide into the head



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Fig. Fig. 27: Checking valve seat concentricity

  1. Remove the cylinder head. On the diesel and the 1,998cc, remove the rocker shaft assembly. On the 1,998cc, lift out the camshaft.
  2.  
  3. Remove the deposits from the combustion chambers with a stiff wire brush and scraper before removing the valves. Do not scratch the cylinder head surface.
  4.  
  5. Compress the valve springs with a valve spring compressor. Remove the valve spring retainer locks and release the springs.
  6.  
  7. Fabricate a valve arrangement board to use when you remove the valves, which will indicate the port in which each valve was originally installed. Also note that the valve keys, caps, etc. should be arranged in a manner which will allow you to install them on the valve on which they were originally used.
  8.  
  9. Remove and discard the valve seals. On models using the umbrella type seals, note the location of the large and small seals for assembly purposes.
  10.  
  11. Thoroughly clean the valves on the wire wheel of a bench grinder, then clean the cylinder head mating surface with a soft wire wheel, a soft wire brush, or a wooden scraper. Avoid using a metallic scraper, since this can cause damage to the cylinder head mating surface, especially on models with aluminum heads.
  12.  
  13. Using a valve guide cleaner chucked into a drill, clean all of the valve guides.
  14.  
  15. Install each valve into its respective port (guide) of the cylinder head.
  16.  
  17. Mount a dial indicator so that the stem is at 90º to the valve stem, as close to the valve guide as possible.
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  19. Move the valve off its seat, and measure the valve guide-to-stem clearance by rocking the stem back and forth to actuate the dial indicator.
  20.  
  21. Measure the valve stems using a micrometer, and compare to specifications, to determine whether stem or guide wear is responsible for excessive clearance.
  22.  

Consult the Specifications tables earlier in this section.

  1. Check the cylinder head flatness as described under Cylinder Head Removal and Installation.
  2.  

REFACING



Using a valve grinder, resurface the valves according to specifications in this section.

All machine work should be performed by a competent, professional machine shop. Valve face angle is not always identical to valve seat angle.

Reface the valves with a refacing tool, following the instructions of the tool manufacturer. See illustrations for dimensions and angles. Remove just enough metal to clean up faces and seats. If, during the refacing process, valve margin becomes less than 1mm (0.04 in.) the valve must be replaced. On the 1,998cc and 2,184cc engines, exhaust valve margin is 1mm (0.04 in.) but intake valve margin need be only 0.5mm (0.00197 in.) or more.

On the diesel, there is no margin limit, provided contact width can be brought to specification, which is 1.7-2.3mm (0.0669-0.0906 in.). To check margin width, apply a thin coating of red lead to the valve seat and then press the valve firmly against the seat without rotating it. Then, measure the width of the mark.

LAPPING



This procedure should be performed after the valves and seats have been machined, to insure that each valve mates to each seat precisely.

  1. Invert the cylinder head, lightly lubricate the valve stems, and install the valves in the head as numbered.
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  3. Coat valve seats with fine grinding compound, and attach the lapping tool suction cup to a valve head.
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Moisten the suction cup.

  1. Rotate the tool between your palms, changing position and lifting the tool often to prevent grooving.
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  3. Lap the valve until a smooth, polished seat is evident.
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  5. Remove the valve and tool, and rinse away all traces of grinding compound.
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VALVE SPRING TESTING



Place the spring on a flat surface next to a square. Measure the height of the spring, and rotate it against the edge of the square to measure distortion. If spring height varies (by comparison) by more than 1.5mm (0.059 in.) or if distortion exceeds 1.5mm (0.059 in.), replace the spring.

In addition to evaluating the spring as above, test the spring pressure at the installed and compressed (installed height minus valve lift) height using a valve spring tester. Spring pressure should be within 1 lb. of all other springs in either position.

VALVE AND SPRING INSTALLATION



Be sure that all traces of lapping compound have been cleaned off before the valves are installed.

  1. Lubricate all of the valve stems with a light coating of engine oil, then install the valves into the proper ports/ guides.
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  3. If umbrella-type valve seals are used, install them at this time. Be sure to use a seal protector to prevent damage to the seals as they are pushed over the valve keeper grooves. If O-ring seals are used, don't install them yet.
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  5. Install the valve springs and the spring retainers, and using the valve compressing tool, compress the springs.
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  7. If umbrella-type seals are used, just install the valve keepers (white grease may be used to hold them in place) and release the pressure on the compressing tool. If O-ring type seals are used, carefully work the seals into the second groove of the valve (closest to the head), install the valve keepers and release the pressure on the tool.
  8.  

If the O-ring seals are installed BEFORE the springs and retainers are compressed, the seal will be destroyed.

  1. After all of the valves are installed and retained, tap each valve spring retainer with a rubber mallet to seat the keepers in the retainer.
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