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VALVE GUIDE Subaru Impreza WRX STI GR

Engine Mechanical (H4DOTC) (except Sti) 5 illustrations ~531 words

VALVE GUIDE

  1. Check the clearance between valve guide and valve stem. The clearance can be checked by measuring respectively the outer diameter of valve stem with a micrometer and the inner diameter of valve guide with a caliper gauge. Clearance between the valve guide and valve stem: Standard Intake 0.030 - 0.057 mm (0.0012 - 0.0022 in) Exhaust 0.040 - 0.067 mm (0.0016 - 0.0026 in)
  2. If the clearance between valve guide and valve stem exceeds the standard, replace the valve guide or valve itself, whichever shows the greater amount of wear or damage. See the following procedure for valve guide replacement.

Valve guide inner diameter

6.000 - 6.012 mm (0.2362 - 0.2367 in)

Valve stem outer diameters

Intake

5.955 - 5.970 mm (0.2344 - 0.2350 in)

Exhaust

5.945 - 5.960 mm (0.2341 - 0.2346 in)

Scheme 721

Scheme 721
Scheme 721

Scheme 722

Scheme 722
Scheme 722

Scheme 723

Scheme 723
Scheme 723

Scheme 724

Scheme 724
Scheme 724
  1. Place the cylinder head on ST1 with the combustion chamber upward so that valve guides fit the holes in ST1.
  2. Insert the ST2 into valve guide and press it down to remove the valve guide. ST1 498267600 CYLINDER HEAD TABLE ST2 499767200 VALVE GUIDE REMOVER
  3. Turn the cylinder head upside down and place the ST as shown in the figure. ST 18251AA020 VALVE GUIDE ADJUSTER
  4. Before installing a new valve guide, make sure that neither scratches nor damages exist on the inner surface of valve guide holes in cylinder head.
  5. Put a new valve guide, coated with sufficient oil, in the cylinder head, and insert the ST1 into valve guide. Press in until the valve guide upper end is flush with the upper surface of ST2. ST1 499767200 VALVE GUIDE REMOVER ST2 18251AA020 VALVE GUIDE ADJUSTER
  6. Check the valve guide protrusion. Valve guide protrusion L: 15.8 - 16.2 mm (0.622 - 0.638 in)
  7. Ream the inside of valve guide using ST. Put the ST in valve guide, and rotate the ST slowly clockwise while pushing it lightly. Bring the ST back while rotating it clockwise. NOTE: Apply engine oil to the ST when reaming. If the inner surface of valve guide is damaged, the edge of ST should be slightly ground with oil stone. If the inner surface of valve guide becomes lustrous and the ST does not chip, use a new ST or remedy the ST. ST 499767400 VALVE GUIDE REAMER
  8. After reaming, clean the valve guide to remove chips.
  9. Recheck the contact condition between valve and valve seat after replacing the valve guide.

Scheme 725

Scheme 725: INTAKE AND EXHAUST VALVE
Scheme 725: INTAKE AND EXHAUST VALVE
  1. Inspect the flange of valve and valve stem, and replace the valve with a new part if damaged, worn, deformed, or if dimension "H" in the figure is outside of the specified limit. Head edge thickness H: Standard Intake (A) 1.0 - 1.4 mm (0.039 - 0.055 in) Exhaust (B) 1.3 - 1.7 mm (0.051 - 0.067 in)
  2. Put a small amount of grinding compound on the valve seat surface, and lap the valve and valve seat surface. Replace with a new valve oil seal after lapping.

Note. It is possible to differentiate between the intake valve and the exhaust valve by their overall length.

Valve overall length

Intake

104.4 mm (4.110 in)

Exhaust

104.65 mm (4.1201 in)