Valve and Valve Seat-Refacing
Fig. 29
VALVE INSPECTION
1. Clean valves thoroughly and discard burned, warped and cracked valves.
2. Measure valve stems for wear. Refer to Engine; Specifications.
CAUTION: Valve stems are chrome plated and should not be polished.
3. Remove carbon and varnish deposits from inside of valve guides with a reliable guide cleaner.
4. Measure valve stem guide clearance as follows:
a. Install valve into cylinder head so it is 14 mm (0.551 inch) off the valve seat. A small piece of hose may be used to hold valve in place.
Fig. 28
b. Attach dial indicator Tool C-3339 to cylinder head and set it at right angle of valve stem being measured (Fig. 28).
5. Move valve to and from the indicator. Refer to Engine; Specification.
6. Ream the guides for valves with oversized stems if dial indicator reading is excessive or if the stems are scuffed or scored.
7. Service valves with oversize stems and over size seals are available in 0.15 mm (0.005 inch), 0.40 mm (0.015 inch) and 0.80 mm (0.030 inch) oversize.
NOTE: Oversize seals must be used with oversize valves.
8. Refer to Valve Guide Specification Chart for reamer size to accommodate the oversize valve stems.
9. Slowly turn reamer by hand and clean guide thoroughly before installing new valve. Do not attempt to ream the valve guides from standard directly to 0.80 mm (0.030 inch) Use step procedure of 0.15 mm (0.005 inch), 0.40 mm (0.015 inch) and 0.80 mm (0.030 inch) so the valve guides may be reamed true in relation to the valve seat. After reaming guides, the seat runout should be measured and resurfaced if necessary. See Refacing Valves and Valve Seats.
VALVE GUIDE SPECIFICATION CHART
VALVE GUIDES
NOTE: Replace cylinder head if guide does not clean up with 0.80 mm (0.030 inch) oversize reamer, or if guide is loose in cylinder head.
REFACING VALVES AND VALVE SEATS
Fig. 30
The intake and exhaust valves have a 44-1/2 to 45 degree face angle. The valve seats have a 45 to 45-1/2 degree face angle. The valve face and valve seat angles are shown in (Fig. 30).
VALVES
1. Inspect the remaining margin after the valves are refaced. Refer to Engine; Specifications.
VALVE SEATS
Fig. 31
CAUTION: Remove metal from valve seat only. Do not remove metal from cylinder head (Fig. 31).
1. 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.
2. Measure the concentricity of valve seat using dial indicator. Total runout should not exceed 0.051 mm (0.002 inch) total indicator reading.
3. Inspect the valve seat using 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 valve face, lower valve seat with a 15 degree stone. If the blue is transferred to the bottom edge of valve face raise valve seat with a 65 degrees stone.
NOTE: Valve seats which are worn or burned can be reworked, provided that correct angle and seat width are maintained. Otherwise cylinder head must be replaced.
4. When seat is properly positioned the width of intake seats should be 1.75 to 2.25 mm (0.69 to 0.088 inch) The width of the exhaust seats should be 1.50 to 2.00 mm (0.059 to 0.078 inch) (Fig. 30).
Fig. 33
5. Check the valve spring installed height after refacing the valve and seat (Fig. 33).
TESTING VALVE SPRINGS
Fig. 32
Whenever valves have been removed for inspection, reconditioning or replacement, valve springs should be tested (Fig. 32). As an example; the compression length of the spring to be tested is 33.34 mm (1-5/16 inches). Turn table of Tool C-647 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. 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. Refer to specifications to obtain specified height and allowable tensions. Discard the springs that do not meet specifications.