Valve: Service and Repair
REFACING VALVES AND VALVE SEATS
1. The intake and exhaust valve seats and valve face have a 45 degree angle.
2. Inspect the remaining margin after the valves are refaced. Intake valves with less than 95 mm (1/32 inch.) margin and Exhaust valves with less than 1.05 mm (3/64 inch) margin should be discarded.
3. When refacing valve seats, it is important that the correct size valve guide pilot be used for reseating stones. A true and complete surface must be obtained.
4. Measure the concentricity of valve seat and valve guide using a valve seat runout dial indicator. Total runout should not exceed 0.051 mm (0.002 inch.) (total indicator reading).
5. 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 15 degrees stone. If the blue is transferred to the bottom edge of valve face, raise valve seat with a 65 degrees stone.
- Intake valve seat diameter is 33 mm (1.299 inch.)
- Exhaust valve seat diameter is 28 mm (1.102 inch.)
Valve seats which are worn or burned can be reworked, provided that correct angle and seat width are maintained. Otherwise the cylinder head must be replaced.
6. When seat is properly positioned the width of intake and exhaust seats should be 0.9 to 1.3 mm (0.35 to 0.051 inch.).
7. Check valve tip to spring seat dimensions A after grinding the valve seats or faces. Grind valve tip to 47.99 mm (1.889 in.) for exhaust valve and 48.04 mm (1.891 in.) for intake valve over spring seat when installed in the head. The valve tip chamfer may need to be reground to prevent seal damage when the valve is installed.
NOTEThis is not valve spring height measurement. See valve installation procedures for height measurement.
REMOVAL
1. With cylinder head removed, compress valve springs using Special Tool MD 998735 or equivalent.
2. Remove valve retaining locks, valve spring retainers, valve stem seals and valve springs.
3. Before removing valves, remove any burrs from valve stem lock grooves to prevent damage to the valve guides. Identify valves to insure installation in original location.
VALVE INSTALLATION
1. Coat valve stems with clean engine oil and insert in cylinder head.
2. Install new valve stem seals on all valves using a valve stem seal tool. The valve stem seals should be pushed firmly and squarely over valve guide.
CAUTION: When oversize valves are used, the corresponding oversize valve seal must also be used. Excessive guide wear may result if oversize seals are not used with oversize valves.
3. Install valve springs and retainers. Compress valve springs only enough to install locks, taking care not to misalign the direction of compression. Nicked valve stems may result from misalignment of the valve spring compressor.
CAUTION: When depressing the valve spring retainers with valve spring compressor the locks can become dislocated. Check to make sure both locks are in their correct location after removing tool.
4. Check the valve spring installed height B after refacing the valve and seat. Make sure measurements are taken from top of spring seat to the bottom surface of spring retainer. If height is greater than 39.20 mm (1.543 in.), install a .762 mm (0.030 inch.) spacer under the valve spring seat to bring spring height back within specification.
5. Install rocker arm shafts as previously described in this section.
6. Checking dry lash. Dry lash is the amount of clearance that exists between the base circle of an installed cam and the rocker arm roller when the adjuster is drained of oil and completely collapsed. Specified dry lash is 1.17 mm (0.046 in.) for intake and 1.28 mm (0.050 in.) for exhaust. After performing dry lash check, refill adjuster with oil and allow 10 minutes for adjuster/s to bleed down before rotating cam.