Cylinder Head and Valves
REMOVAL AND INSTALLATION
REMOVAL SERVICE POINTS
[[A]] CYLINDER HEAD BOLT REMOVAL
Using the special tool MD991653 to loosen the cylinder head bolts.
[[B]] RETAINER LOCK REMOVAL
1. Using special tool MD998772 or MD998735, compress the retainer locks.
2. Remove the retainer locks.
NOTE: Tag removed valves, springs end other components, noting their cylinder numbers and locations to facilitate reassembly. Store these components safely.
[[C]] VALVE STEM SEAL REMOVAL
Do not reuse removed valve stem seal.
INSTALLATION SERVICE POINTS
]]A[[ VALVE STEM SEAL INSTALLATION
1. Install the valve spring seat.
2. Using special tool MD998774, install a new stem seal to the valve guide.
CAUTION:
^ Do not reuse removed valve stem seals.
^ The valve stem seal must be installed using the correct special tool. Incorrect installation could result in oil leaking past the valve guide.
]]B[[ VALVE SPRING INSTALLATION
Install the valve spring so that the painted end is on the rocker arm side.
]]C[[ RETAINER LOCK INSTALLATION
Using special tool MD998772 or MD998735, compress the valve spring and insert the retainer lock into position.
NOTE: The valve if excessively compressed, causes the bottom end of retainer to be in contact with the stem seal, and damage it.
]]D[[ CYLINDER HEAD BOLT INSTALLATION
1. Before reusing the cylinder head bolt, measure that its shank length does not exceed the specified limit. Replace the bolt if this measurement exceeds the limit.
Limit: Maximum 96.4 mm (3.795 inches)
2. Fit the washer as shown.
3. Apply engine oil to the bolt thread and washer.
4. Tighten the bolts in the sequence shown until each is torqued to 74 Nm (54 ft. lbs.) using the cylinder head bolt wrench special tool (MB991653).
5. Loosen all bolts fully.
6. Retighten the bolts in the sequence shown until each is torqued to 20 Nm (15 ft. lbs.).
7. Make paint marks on the cylinder head bolt heads and cylinder head as shown.
8. In accordance with the tightening sequence, tighten each bolt by 90 degree angle (1/4 turn).
9. Tighten each bolt by further 90 degree angle (1/4 turn) and check that the paint marks on the bolt head and cylinder head are aligned.
CAUTION: If the bolts are tightened by an angle of less than 90 degree angle (1/4 turn), they may not hold the cylinder head with sufficient strength. If the bolts are tightened by an angle exceeding 90 degree angle, completely remove them and repeat the installation procedure.
INSPECTION
CYLINDER HEAD
1. Before cleaning the cylinder head, check it for water leaks, gas leaks, cracks, and other damage.
2. Remove all oil, water scale, sealant, and carbon. After cleaning the oil passages, blow air through them to verify that they are not blocked.
3. Check the cylinder head gasket surface for flatness by using a straight edge and feeler gauge.
Standard value: 0.03 mm (0.0012 inch)
Limit: 0.2 mm (0.008 inch)
4. If flatness exceeds the specified limit, grind the gasket surface to specification.
Grinding limit: *0.2 mm (0.008 inch)
*Includes/combined with cylinder block grinding
Cylinder head height (Specification when new): 119.9 - 120.1 mm (4.720 - 4.728 inches)
VALVE
1. Check the valve face for correct contact. If contact is uneven or incomplete, reface the valve seat.
2. If the margin is less than specified, replace the valve.
Standard value:
Intake: 1.0 mm (0.039 inch)
Exhaust: 1.3 mm (0.051 inch)
Limit:
Intake: 0.5 mm (0.020 inch)
Exhaust: 0.8 mm (0.031 inch)
3. Measure the valve length. If the measurement is less than specified, replace the valve.
Standard value:
Intake: 110.15 mm (4.337 inches)
Exhaust: 113.70 mm (4.476 inches)
Limit:
Intake: 109.65 mm (4.317 inches)
Exhaust: 113.20 mm (4.457 inches)
VALVE SPRING
1. Measure the valve spring free height. If the measurement is less than specified, replace spring.
Standard value: 49.5 mm (1.95 inches)
Limit: 48.5 mm (1.91 inches)
2. Measure the squareness of the spring. If the measurement is less than specified, replace the spring.
Standard value: 2° or less
Limit: 4°
VALVE GUIDE
Measure the clearance between the valve guide and valve stem. If the clearance exceeds the specified limit, replace valve guide or valve, or both.
Standard value:
Intake: 0.02 - 0.05 mm (0.0008 - 0.0020 inch)
Exhaust: 0.04 - 0.06 mm (0.0016 - 0.0024 inch)
Limit:
Intake: 0.10 mm (0.0039 inch)
Exhaust: 0.15 mm (0.0059 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:
Intake: 49.30 mm (1.9409 inches)
Exhaust: 49.35 mm (1.9429 inches)
Limit
Intake: 49.80 mm (1.9606 inches)
Exhaust: 49.85 mm (1.9626 inches)
VALVE SEAT RECONDITIONING PROCEDURE
1. Before correcting the valve seat, check the clearance between the valve guide and valve. If necessary, replace the valve guide.
2. Using the appropriate special tool or seat grinder, correct the valve seat to achieve 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 to be replaced from the inside to reduce the wall thickness. Then, remove the valve seat.
2. Rebore the valve seat hole in the cylinder head to match the selected oversize valve seat diameter.
Intake valve seat hole diameter
0.3 oversize: 31.80 - 31.83 mm (1.2520 - 1.2531 inches)
0.6 oversize: 32.10 - 32.13 mm (1.2638 - 1.2650 inches)
Exhaust valve seat hole diameter
0.3 oversize: 29.30 - 29.32 mm (1.1535 - 1.1543 inches)
0.6 oversize: 29.60 - 29.62 mm (1.1654 - 1.1661 inches)
3. Prevent galling of the cylinder head bore by cooling the valve seat with liquid nitrogen before press-fitting it.
4. Correct the valve seat to achieve the specified width and angle.
VALVE GUIDE REPLACEMENT PROCEDURE
1. Using a press, push the valve guide out toward the cylinder block side.
2. Rebore the valve guide hole in the cylinder head to match the oversize valve guide that is to be fitted.
CAUTION: Do not install a valve guide of the same size again.
Valve guide hole diameters in cylinder head
0.05 oversize: 11.05 - 11.07 mm (0.4350 - 0.4358 inch)
0.25 oversize: 11.25 - 11.27 mm (0.4429 - 0.4337 inch)
0.50 oversize: 11.50 - 11.52 mm (0.4528 - 0.4535 inch)
3. Press-fit the valve guide until it projects by the specified amount.
Standard value: 14.0 mm (0.551 inch)
CAUTION:
^ The valve guide must be installed from the upper side of the cylinder head.
^ The valve guides differ in length on the intake and exhaust sides.
Valve guide length
Intake: 45.5 mm (1.791 inches)
Exhaust: 50.5 mm (1.988 inches)
4. After press-fitting the valve guide, insert a new valve and check that it slides smoothly.