CLEAN CYLINDER HEAD SUB-ASSEMBLY

INSPECT CYLINDER HEAD SUB-ASSEMBLY

CLEAN VALVE SEAT

INSPECT INTAKE VALVE

INSPECT EXHAUST VALVE

INSPECT VALVE GUIDE BUSH OIL CLEARANCE

INSPECT INTAKE VALVE SEAT

INSPECT EXHAUST VALVE SEAT

INSPECT INNER COMPRESSION SPRING

Using a gasket scraper, remove all the gasket material from the surface which contacts the cylinder block.

• NOTICE:

• Be careful not to scratch the surface which contacts the cylinder block.

Using a wire brush, remove all the carbon from the combustion chambers.

• NOTICE:

• Be careful not to scratch the cylinder block contact surface.

Using a valve guide bushing brush and solvent, clean all the guide bushes.

Using a soft brush and solvent, thoroughly clean the cylinder head.

Using a precision straightedge and feeler gauge, measure the warpage of the surfaces which contact the cylinder block sub-assembly and manifolds.

• Standard Warpage:

• Item	Specified Condition
  Cylinder block side	0.05 mm (0.00197 in.)
  Intake side	0.08 mm (0.00315 in.)
  Exhaust side	0.08 mm (0.00315 in.)

• Maximum Warpage:

• Item	Specified Condition
  Cylinder block side	0.10 mm (0.00394 in.)
  Intake side	0.10 mm (0.00394 in.)
  Exhaust side	0.10 mm (0.00394 in.)

If the warpage is more than the maximum, replace the cylinder head sub-assembly.

Using a dye penetrant, check the intake ports, exhaust ports and cylinder surface for cracks.

If cracked, replace the cylinder head sub-assembly.

Using a 45° carbon cutter, resurface the valve seats.

• HINT:

• Only remove the amount of metal necessary to clean the seats.

Clean the valves.

Using a micrometer, measure the diameter of the valve stem.

• Valve stem diameter:
• 5.470 to 5.485 mm (0.215 to 0.216 in.)

If the valve stem diameter is not as specified, check the oil clearance.

Check the valve face angle.

Using a vernier caliper, measure the valve head margin thickness.

• Standard margin thickness:
• 1.25 mm (0.0492 in.)

• Minimum margin thickness:
• 0.5 mm (0.0197 in.)

If the margin thickness is less than the minimum, replace the intake valve.

Using a vernier caliper, measure the valve overall length.

• Standard overall length:
• 105.85 mm (4.17 in.)

• Minimum overall length:
• 105.35 mm (4.15 in.)

If the overall length is less than the minimum, replace the intake valve.

Clean the valves.

Using a micrometer, measure the diameter of the valve stem.

• Valve stem diameter:
• 5.465 to 5.480 mm (0.215 to 0.216 in.)

If the valve stem diameter is not as specified, check the oil clearance.

Check the valve face angle.

Using a vernier caliper, measure the valve head margin thickness.

• Standard margin thickness:
• 1.4 mm (0.0551 in.)

• Minimum margin thickness:
• 0.5 mm (0.0197 in.)

If the margin thickness is less than the minimum, replace the exhaust valve.

Using a vernier caliper, measure the valve overall length.

• Standard overall length:
• 110.40 mm (4.35 in.)

• Minimum overall length:
• 109.90 mm (4.33 in.)

If the overall length is less than the minimum, replace the exhaust valve.

Using a caliper gauge, measure the inside diameter of the valve guide bush.

• Bush inside diameter:
• 5.510 to 5.530 mm (0.217 to 0.218 in.)

Subtract the valve stem diameter measurement from the valve guide bush inside diameter measurement.

• Standard Oil Clearance:

• Item	Specified Condition
  Intake	0.025 to 0.060 mm (0.000984 to 0.00236 in.)
  Exhaust	0.030 to 0.065 mm (0.00118 to 0.00256 in.)

• Maximum Oil Clearance:

• Item	Specified Condition
  Intake	0.08 mm (0.00315 in.)
  Exhaust	0.10 mm (0.00394 in.)

If the clearance is more than the maximum, replace the valve and valve guide bush.

Apply a light coat of Prussian blue to the valve face.

Lightly press the valve face against the valve seat.

• NOTICE:

• Do not rotate the valve.

Check the valve face and valve seat by using the following procedure:

Apply a light coat of Prussian blue to the valve face.

Lightly press the valve face against the valve seat.

• NOTICE:

• Do not rotate the valve.

Check the valve face and valve seat by using the following procedure:

Using a vernier caliper, measure the free length of the inner compression spring.

• Standard free length:
• 48.63 mm (1.91 in.)

If the free length is not as specified, replace the inner compression spring.

Using a steel square, measure the deviation of the inner compression spring.

• Maximum deviation:
• 1.0 mm (0.0394 in.)

• Maximum angle (reference):
• 2°

If the deviation is more than the maximum, replace the inner compression spring.

Using a spring tester, measure the tension of the valve spring when it is compressed to the specified installation length.

• Standard installed tension:
• 235.6 to 260.4 N (24 to 27 kgf, 53.0 to 58.5 lbf) at 36.9 mm (1.45 in.)

If the installed tension is not as specified, replace the valve spring.