Cylinder Head and Valves
CYLINDER HEAD AND VALVEDISASSEMBLY AND REASSEMBLY
Disassembly Steps 1-21:
SERVICE POINTS OF DISASSEMBLY
1. REMOVAL OF CYLINDER HEAD BOLT
Using the special tool, remove the cylinder head bolts.
5./10. REMOVAL OF RETAINER LOCK
Depress valve spring using the special tool and remove the retainer lock. Keep these parts in order for reassembly.
15./16. REMOVAL OF VALVE STEM SEAL
Remove the valve stem seals with pliers.
INSPECTION
- CYLINDER HEAD
1. Before cleaning, check for leaks, damage and cracks.
2. Clean cylinder head and oil passage.
3. Check cylinder head for flatness.
Standard value: 0.05 mm (0.0020 in.) or less
Limit: 0.2 mm (0.008 in.)
4. If the measured flatness exceeds the limit, grind and repair the surface to gain the flatness of standard value.
Grinding limit: 0.2 mm (0.008 in.)*
Cylinder head overall height: 132 mm (5.197 in.)
* Maximum of 0.2 mm (0.008 in.) for grinding is permitted.
CAUTION: This is a combined total dimension of stock removal from cylinder head (if any) and cylinder block top surface.
- VALVES
1. Clean valves thoroughly and discard burned, warped and cracked valve.
2. Check valve stem tip for pitting or depression of Point A.
3. Check for wear and ridge wear at Point B.
4. Check for even contact (at face center) with valve seat, Point C.
5. Check margin. Replace valve if margin exceeds limit.
Standard value:
Intake : 1.0 mm (0.040 in.)
Exhaust : 1.5 mm (0.059 in.)
Limit:
Intake : 0.7 mm (0.028 in.)
Exhaust : 1.0 mm (0.040 in.)
6. Measure valve stem to guide clearance. Replace valve and/or valve guide if clearance exceeds limit.
Standard value:
Intake : 0.02-0.047 mm (0.0008- 0.0019 in.)
Exhaust : 0.05-0.085 mm (0.002- 0.0033 in.)
Limit:
Intake : 0.10. mm (0.004 in.)
Exhaust : 0.15 mm (0.006 in.)
- VALVE SPRINGS
1. Check free length of each valve spring and replace if necessary.
Standard value: 48.3 mm (1.902 in.)
Limit: 47.3 mm (1.862 in.)
2. Using a square, test squareness of each valve spring. If spring is excessively out of square, replace it.
Standard value: Max. 1.5°
Limit: 4°
VALVE SEAT RECONDITIONING PROCEDURES
1. Before valve seat reconditioning, check valve stem to guide clearance.
2. Recondition the valve seat with a seat grinder or cutter. The valve seat width should be the specified value at the center of the valve face.
Inspect the valve seat with Prussian blue to determine where the valve contacts the seat. To do this, coat valve seat lightly with Prussian blue then set valve in place. Rotate the valve with light pressure. If the blue is transferred to the center of valve face, contact is satisfactory.
If the blue is transferred to top edge of the valve face, lower valve seat with a 30 degrees stone or cutter. If the blue is transferred to the bottom edge of valve face, raise valve seat with a 65 degrees stone or cutter.
Valve seat diameter:
Intake : 31.8 mm (1.25 in.)
Exhaust : 29.4 mm (1.16 in.)
Seat width: 0.9-1.3 mm (0.035-0.051 in.)
3. The valve and valve seat should be lapped with a lapping compound.
4. Check valve seat sinkage.
The amount of valve seat sinkage can be determined by measuring the installed height of the valve spring. (The installed height of the valve spring will also become greater if the amount of valve seat sinkage becomes greater.) If the valve spring installed height exceeds the service limit. replace the insert with an oversize part as described below.
Installed height of spring (both intake and exhaust)
Standard value: 40.0 mm (1.575 in.)
Limit: 41.0 mm (1.614 in.)
VALVE SEAT INSERT REPLACEMENT PROCEDURES
1. Scrape the inner side of the valve seat insert to reduce the wall thickness and remove.
2. Machine the press fit diameter of the valve seat on the cylinder head side so that it matches the diameter and height of the oversize valve seat.
Valve Seat Oversizes
3. Heat the cylinder head to about 250 °C (480 °F) and press in an oversize seat insert into the cylinder head.
NOTE: Be sure not to overheat the valve seat.
4. Process the valve seat 59 that it becomes the dimensions shown in the figure.
Valve seat diameter:
Intake : 31.8 mm (1.25 in.)
Exhaust : 29.4 mm (1.16 in.)
Seat width: 0.9-1.3 mm (0.035-0.051 in.)
5. Use the lapping compound. and lap the valve.
6. Ensure that the seat is properly centered on the valve face.
VALVE GUIDE REPLACEMENT PROCEDURE
1. Using suitable rod and a press, press the valve guide out of the cylinder head toward the cylinder block side.
2. Rebore the valve guide hole to the oversize valve guide outside diameter to be press4itted.
CAUTION: Do not use a value guide of the same size as the one removed.
3. Install the valve guide until a protrusion of 19.5 mm (.768 in.) is obtained. See the illustration.
NOTE:
1. Press-fit the valve guide from the cylinder head top surface.
2. Note the difference in lengths of the valve guides for the intake and exhaust: intake 45.5 mm (1.791 in.) and exhaust 50.5 mm (1.988 in.).
3. After the valve guide has been installed in position, insert a new valve to ensure that it slides smoothly.
SERVICE POINTS OF REASSEMBLY
16./15. INSTALLATION OF VALVE STEM SEAL
1. Install the spring seat onto cylinder head.
2. Using special tool install the valve stem seal by lightly tapping the tool.
Cautions:
1. Incorrect installation of the seal without using Special Tool will result in poor sealing and cause oil leakage down valve guide.
2. Do not reuse stem seal.
12./7. INSTALLATION OF VALVE SPRING
Valve springs should be installed with the enamel coated side toward the valve spring retainer.
10./5 INSTALLATION OF RETAINER LOCK
Depress valve spring using the valve spring compressor and install retainer lock.
CAUTION: When compressing the spring with the valve spring compressor, check to see that the valve stem seal is not pressed to the bottom of the retainer. Then start installing the retainer lock.
4. INSTALLATION OF CYLINDER HEAD GASKET
1. Clean both gasket surfaces of the cylinder block and cylinder head.
2. Place a new cylinder head gasket onto the cylinder block.
Identification mark: 20
1. INSTALLATION OF CYLINDER HEAD BOLTS
Using the special tool, tighten the cylinder head bolts.