Valve and Valve Seat-Refacing
Fig. 33
The intake and exhaust valves have a 44.5 to 45° face angle. The valve seats have a 45 to 45.5° face angle. The valve face and valve seat angles are shown in (Fig. 33).
VALVES
Inspect the remaining margin after the valves are refaced. Refer to Cylinder Head Assembly, Valve, Intake/Exhaust Specifications.
VALVE SEATS
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 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 valve face, then lower valve seat with a 15° stone. If the blue is transferred to the bottom edge of valve face, then raise valve seat with a 65° 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.
Fig. 33
4. When seat is properly positioned the width of the intake 1.00 to 1.50 mm (0.0394 to 0.0591 inch) and exhaust seats should be 1.25 to 1.75 mm (0.049 to 0.069 inch) (Fig. 33).
Fig. 35
5. Check the valve spring installed height after refacing the valve and seat (Fig. 35).
VALVE SPRINGS
The valve springs are common for intake and exhaust valves. Refer to Cylinder Head Assembly, Valve Spring, Specifications.
TESTING VALVE SPRINGS
Fig. 34
Whenever valves have been removed for inspection, reconditioning or replacement, valve springs should be tested (Fig. 34). As an example; the compression length of the spring to be tested is 38.00 mm (1.496 inch). Turn table of Tool C-647 until surface is in line with the 38.00 mm (1.496 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 Cylinder Head Assembly, Valve Spring, Specifications to obtain specified height and allowable tensions. Replace any springs that do not meet specifications.
VALVE INSTALLATION
1. Coat valve stems with clean engine oil and insert them in cylinder head.
2. If valves or seats have been reground, check valve tip height (A) (Fig. 35). If valve tip height for intake valve is greater than 47.59 (1.8737 inch) or 49.14 (1.9347 inch) for exhaust valve, grind valve tip until within specifications. Make sure measurement is taken from cylinder head surface to the top of valve stem.
Fig. 36
3. Install valve seal/spring seat assembly over valve guides on all valve stems (Fig. 36). Ensure that the garter spring is intact around the top of the rubber seal. Install valve springs, valve retainers.
4. Compress valve springs with a valve spring compressor install locks and release tool. If valves and/or seats are reground, measure the installed height of springs (B) (Fig. 35), make sure measurements are taken from top of spring seat to the bottom surface of spring retainer. If height is greater than 38.75 mm (1.5256 inch), install a 0.762 mm (0.030 inch) spacer in head counterbore under the valve spring seat to bring spring height back within specification.