Valve and Valve Seat-Refacing
REMOVAL1. With cylinder head removed, compress valve springs using Special Tool C-3422-B with Adaptor 6526.
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 INSPECTION
1. Clean valves thoroughly and discard burned, warped and cracked valves.
2. Measure valve stems for wear. Measure stem about 60 mm beneath the valve lock grooves.
3. If valve stems are worn more than 0.05 mm (0.002 inch), replace valve.
VALVE GUIDES
1. Remove carbon and varnish deposits from inside of valve guides with a reliable guide cleaner.
Fig. 118
2. Using a small hole gauge and a micrometer, measure valve guides in 3 places top, middle and bottom (Fig. 118). Replace guides if they are not within specification. For specifications, refer to General Specifications. Engine Specifications
Fig. 119
3. Check valve guide height (Fig. 119).
TESTING VALVE SPRINGS
Fig. 120
1. Whenever valves have been removed for inspection, reconditioning or replacement, valve springs should be tested Special Tool C-647. As an example, the compression length of the spring to be tested is 33.34 mm (1-5/16 inch). Turn tool table until surface is in line with the 33.34 mm (1-5/16 inch) mark on the threaded stud and the zero mark on the front. Place spring over stud on the table and lift compressing lever to set tone device (Fig. 120). Pull on torque wrench until ping is heard. Take reading on torque wrench at this instant. Multiply this reading by two. This will give the spring load at test length. Fractional measurements are indicated on the table for finer adjustments. Discard the springs that do not meet specifications. The following specifications apply to both intake and exhaust valve springs:
- Valve Closed Nominal Tension-70 lbs. @ 39.8 mm (1.57 inch)
- Valve Closed Nominal Tension-160 lbs. @ 32.6 mm (1.28 inch)
2. Verify springs are not distorted with a steel square and surface plate, check springs from both ends. If the spring is more than 1.5 mm (1/16 inch) out of square, install a new spring.
REFACING VALVES AND VALVE SEATS
1. The intake and exhaust valve seats and valve face have a 45 degree angle.
Fig. 121
2. Inspect the remaining margin after the valves are refaced (Fig. 121). Intake valves with less than 0.95 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. For specifications, refer to General Specifications. Engine Specifications
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.
6. Valve seats which are worn or burned can be reworked, provided that correct angle and seat width are maintained. The intake valve seat must be serviced when the valve seat width is 2.0 mm (0.079 inch) or greater. The exhaust valve seat must be serviced when the valve seat width is 2.5 mm (0.098 inch) or greater. Otherwise the cylinder head must be replaced.
Fig. 122
7. When seat is properly positioned the width of intake and exhaust seats should be 0.75 - 1.25 mm (0.030 - 0.049 inch) (Fig. 122).
Fig. 123
8. Check valve tip to spring seat dimensions A after grinding the valve seats or faces. Grind valve tip until within specifications. Measure from valve tip to spring seat when installed in the head (measurement A) (Fig. 123). For specifications, refer to General Specifications. Engine Specifications The valve tip chamfer may need to be reground to prevent seal damage when the valve is installed.
CLEANING
Clean all valve guides, valves and valve spring assemblies thoroughly with suitable cleaning solution before reassembling.
VALVE INSTALLATION
1. Coat valve stems with clean engine oil and insert in cylinder head.
Fig. 124
2. Install new valve stem seals on all valves using a valve stem seal tool (Fig. 124). The valve stem seals should be pushed firmly and squarely over valve guide.
CAUTION: If oversize valves are used, there is only one oversize valve available. The same stem seal is used on both the
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 after refacing the valve and seat (measurement B) (Fig. 123). Make sure measurements are taken from top of spring seat to the bottom surface of spring retainer. If height is greater than 40.18 mm (1.58 inch), install a 0.762 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.
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 inch) for intake and 1.28 mm (0.050 inch) for exhaust. After performing dry lash check, refill adjuster with oil and allow 10 minutes for adjuster(s) to bleed down before rotating cam.