Cylinder Head and Valves Inspection
CYLINDER HEAD
1. Check the cylinder head gasket surface for flatness by using a straightedge and feeler gauge in the directions of A through G shown in the illustration.
Standard value: 0.03 mm (0.0012 inch)
Limit: 0.2 mm (0.007 inch)
2. If it exceeds the limit, correct to meet the specification.
Grinding limit: *0.2 mm (0.007 inch)
*Includes combined with cylinder block grinding.
Cylinder head height (specification when new): 120 mm (4.7 inches)
VALVE
1. Check the valve seat contact. The valve seat contact should be uniform at the center of the valve face. If incorrect, reface using a valve refacer.
2. If the margin is below the limit, replace the valve.
Standard value:
Minimum limit:
3. Measure the valve's total length. If the measurement is less than the limit, replace the valve.
Standard value:
Minimum limit:
VALVE SPRINGS
1. Measure the free height of the springs. If it is less than the limit, replace.
Standard value: 51.0 mm (2.01 inches)
Minimum limit: 50.0 mm (1.97 inches)
2. Measure the squareness of the springs. If it exceeds the limit, replace.
Standard value: 2° angle
Limit: 4° angle
VALVE GUIDES
Measure the clearance between the valve guide and valve stem. If it exceeds the limit, replace the valve guide or valve, or both.
Standard value:
Intake 0.02 - 0.05 mm (0.0008 - 0.0019 inch)
Exhaust 0.04 - 0.07 mm (0.0016 - 0.0027 inch)
Limit:
Intake 0.10 mm (0.003 inch)
Exhaust 0.15 mm (0.005 inch)
VALVE SEAT
Assemble the valve, then measure the valve stem projection between the end of the valve stem and the spring seating surface. If the measurement exceeds the specified limit, replace the valve seat.
Standard value: 49.30 mm (1.941 inches)
Limit: 49.80 mm (1.960 inches)
VALVE SEAT RECONDITIONING PROCEDURE
1. Before correcting the valve seat, check for the clearance between the valve guide and valve and, if necessary, replace the valve guide.
2. Using the special tool or a seat grinder, correct to obtain the specified seat width and angle.
3. After correcting the valve seat, lap the valve and valve seat using lapping compound. Then, check the valve stem projection.
VALVE SEAT REPLACEMENT PROCEDURE
1. Cut the valve seat from the inside to thin the wall thickness. Then, remove the valve seat.
2. Rebore the valve seat hole in the cylinder head to a selected oversize valve seat diameter.
Seat ring hole diameter:
Intake valve
0.3 OS 34.30 - 34.33 mm (1.3504 - 1.3516 inches)
0.6 OS 34.60 - 34.63 mm (1.3622 - 1.3634 inches)
Exhaust valve
0.3 OS 31.80 - 31.83 mm (1.2520 - 1.2531 inches)
0.6 OS 32.10 - 32.13 mm (1.2638 - 1.2650 inches)
3. Before fitting the valve seat, either heat the cylinder head up to approximately 250°C (482°F) or cool the valve seat in liquid nitrogen, to prevent the cylinder head bore from galling.
4. Using a valve seat cutter, correct the valve seat to the specified width and angle. See "VALVE SEAT RECONDITIONING PROCEDURE" above.
VALVE GUIDE REPLACEMENT PROCEDURE
1. Remove the snap ring from the exhaust valve guide.
2. Using a press, remove the valve guide toward the cylinder block.
CAUTION: Do not install a valve guide of the same size again.
3. Rebore the valve guide hole of the cylinder head so that it fits the press-fitted oversize valve guide.
Valve guide hole diameter:
0.05 OS 11.05 - 11.07 mm (0.4350 - 0.4358 inch)
0.25 OS 11.25 - 11.27 mm (0.4429 - 0.4457 inch)
0.50 OS 11.50 - 11.52 mm (0.4528 - 0.4535 inch)
4. Install the new snap ring into groove of the exhaust valve guide.
NOTE: The inlet valve guide has no snap ring groove.
5. Press-fit the valve guide until it protrudes 14 mm (0.6 inch) from the cylinder head top surface as shown in the illustration.
NOTE: When press-fitting the valve guide, work from the cylinder head top surface.
NOTE: After installing the valve guides, insert new valves in them to check for smooth operation.