INSPECTION

Before cleaning the cylinder head, check it for traces of water and gas leakage and for cracks and any other damage.

Thoroughly remove oils, scale, sealants, carbon and other contamination. Clean the oil passages, then check using compressed air that they are not blocked.

CAUTION

The thickness of the metal that can be removed by grinding from both the cylinder head and the mating cylinder block is limited to 0.2 mm in total.

Check the cylinder head gasket surface for warp using a straightedge and thickness gauge.
If the surface is warped beyond the limit, grind the surface for rectification.

Gasket surface warp

Standard value: Less than 0.05 mm

Limit: 0.2 mm

Grinding limit: 0.2 mm

Cylinder head height (standard value for new part): 131.9 - 132.1 mm

VALVES

Check the valve face for correct contact with the seat. Reface the valve if the contact is partial or one sided.

Measure the margin.
Replace the valve if its margin is smaller than the limit.

Standard values:

Intake 1.0 mm

Exhaust 1.5 mm

Limits:

Intake 0.5 mm

Exhaust 1.0 mm

Measure the total length of the valve.
Replace the valve if the length is less than the limit.

Standard values:

Intake 109.5 mm

Exhaust 109.7 mm

Limits:

Intake 109.0 mm

Exhaust 109.2 mm

VALVE SPRINGS

Measure the free height of the spring.
Replace the spring if its height is smaller than the limit.

Standard value: 47.0 mm
Limit: 46.0 mm

Measure the squareness of the spring.
Replace the spring if it is out of square beyond the limit.

Standard value: 1.5° or smaller
Limit: 4°

VALVE GUIDE

Measure the valve guide inside diameter and valve stem diameter to calculate the clearance between the valve guide and valve stem.
If the limit is exceeded, replace the valve guide or valve, or both.

Standard values:

Intake 0.02 - 0.05 mm

Exhaust 0.05 - 0.09 mm

Limits:

Intake 0.10 mm

Exhaust 0.15 mm

VALVE SEATS

With the valve installed in position and its face pressed against the valve seat, measure the valve stem projection (distance between the valve stem end and spring seating surface). If the measurement exceeds the limit, replace the valve seat.

Standard values:

Intake 49.2 mm

Exhaust 48.4 mm

Limits:

Intake 49.7 mm

Exhaust 48.9 mm

VALVE SEAT RECONDITIONING

Before reconditioning the valve seat, check the clearance between the valve guide and valve stem and, if necessary, replace the valve guide.

Resurface the valve seat to the indicated width and angles.

After resurfacing, lap the valve and valve seat using lapping compound.

VALVE SEAT REPLACEMENT

Cut inside of the valve seat to be replaced until its wall becomes thin enough for removal, then remove the valve seat.

Rebore the valve seat hole in the cylinder head to a diameter matched to the diameter of the selected oversize valve seat.

Intake valve seat hole diameters:

0.3 oversize: 35.30 - 35.33 mm

0.6 oversize: 35.60 - 35.63 mm

Exhaust valve seat hole diameters:

0.3 oversize: 33.30 - 33.33 mm

0.6 oversize: 33.60 - 33.63 mm

Before fitting the valve seat, cool it in liquid nitrogen to prevent damage to its hole in the cylinder head due to interference.

Resurface the valve seat. See the VALVE SEAT RECONDITIONING section.

VALVE GUIDE REPLACEMENT

Force out the valve guide toward the cylinder block using a press.

CAUTION

Do not use a replacement valve guide of the same size as the removed one.

Machine the valve guide hole in the cylinder head to the size matched to the selected oversize valve guide.

Valve guide hole diameters

0.05 oversize: 12.05 - 12.07 mm

0.25 oversize: 12.25 - 12.27 mm

0.50 oversize: 12.50 - 12.52 mm

Press-fit the valve guide until it remains protruded above the cylinder head by the amount indicated in the drawing.

Standard value: 19.2 - 19.8 mm

NOTE: Press the valve guide from above the cylinder head.

NOTE: The valve guides for the intake valves are different in length from those for the exhaust valves (45.5 mm for intake valves; 50.5 mm for exhaust valves)

After installing the valve guide, insert a new valve in it to check for smooth movement.


	INSPECTION

	CYLINDER HEAD Before cleaning the cylinder head, check it for traces of water and gas leakage and for cracks and any other damage. Thoroughly remove oils, scale, sealants, carbon and other contamination. Clean the oil passages, then check using compressed air that they are not blocked.
	CAUTION The thickness of the metal that can be removed by grinding from both the cylinder head and the mating cylinder block is limited to 0.2 mm in total. Check the cylinder head gasket surface for warp using a straightedge and thickness gauge. If the surface is warped beyond the limit, grind the surface for rectification. Gasket surface warp Standard value: Less than 0.05 mm Limit: 0.2 mm Grinding limit: 0.2 mm Cylinder head height (standard value for new part): 131.9 - 132.1 mm

	VALVES Check the valve face for correct contact with the seat. Reface the valve if the contact is partial or one sided.
	Measure the margin. Replace the valve if its margin is smaller than the limit. Standard values: Intake 1.0 mm Exhaust 1.5 mm Limits: Intake 0.5 mm Exhaust 1.0 mm
	Measure the total length of the valve. Replace the valve if the length is less than the limit. Standard values: Intake 109.5 mm Exhaust 109.7 mm Limits: Intake 109.0 mm Exhaust 109.2 mm

	VALVE SPRINGS
	Measure the free height of the spring. Replace the spring if its height is smaller than the limit. Standard value: 47.0 mm Limit: 46.0 mm Measure the squareness of the spring. Replace the spring if it is out of square beyond the limit. Standard value: 1.5° or smaller Limit: 4°

	VALVE GUIDE
	Measure the valve guide inside diameter and valve stem diameter to calculate the clearance between the valve guide and valve stem. If the limit is exceeded, replace the valve guide or valve, or both. Standard values: Intake 0.02 - 0.05 mm Exhaust 0.05 - 0.09 mm Limits: Intake 0.10 mm Exhaust 0.15 mm

	VALVE SEATS
	With the valve installed in position and its face pressed against the valve seat, measure the valve stem projection (distance between the valve stem end and spring seating surface). If the measurement exceeds the limit, replace the valve seat. Standard values: Intake 49.2 mm Exhaust 48.4 mm Limits: Intake 49.7 mm Exhaust 48.9 mm
	VALVE SEAT RECONDITIONING Before reconditioning the valve seat, check the clearance between the valve guide and valve stem and, if necessary, replace the valve guide.
	Resurface the valve seat to the indicated width and angles. After resurfacing, lap the valve and valve seat using lapping compound.
	VALVE SEAT REPLACEMENT
	Cut inside of the valve seat to be replaced until its wall becomes thin enough for removal, then remove the valve seat.
	Rebore the valve seat hole in the cylinder head to a diameter matched to the diameter of the selected oversize valve seat. Intake valve seat hole diameters: 0.3 oversize: 35.30 - 35.33 mm 0.6 oversize: 35.60 - 35.63 mm Exhaust valve seat hole diameters: 0.3 oversize: 33.30 - 33.33 mm 0.6 oversize: 33.60 - 33.63 mm Before fitting the valve seat, cool it in liquid nitrogen to prevent damage to its hole in the cylinder head due to interference. Resurface the valve seat. See the VALVE SEAT RECONDITIONING section.
	VALVE GUIDE REPLACEMENT Force out the valve guide toward the cylinder block using a press. CAUTION Do not use a replacement valve guide of the same size as the removed one. Machine the valve guide hole in the cylinder head to the size matched to the selected oversize valve guide. Valve guide hole diameters 0.05 oversize: 12.05 - 12.07 mm 0.25 oversize: 12.25 - 12.27 mm 0.50 oversize: 12.50 - 12.52 mm
	Press-fit the valve guide until it remains protruded above the cylinder head by the amount indicated in the drawing. Standard value: 19.2 - 19.8 mm NOTE: Press the valve guide from above the cylinder head. NOTE: The valve guides for the intake valves are different in length from those for the exhaust valves (45.5 mm for intake valves; 50.5 mm for exhaust valves) After installing the valve guide, insert a new valve in it to check for smooth movement.