Valve Service
VALVE CLEANINGClean valves thoroughly Discard burned, warped and cracked valves.
Remove carbon and varnish deposits from inside of valve guides with a reliable guide cleaner.
VALVE INSPECTION
Measure valve stems for wear. If wear exceeds 0.051 mm (0.002 inch), replace the valve.
REFACING VALVES AND VALVE SEATS
Valve Face And Seat Angles:
The intake and exhaust valves have a 43-1/4° to 43-3/4° face angle and a 44-1/4° to 44-3/4° seat angle.
VALVES
Intake And Exhaust Valves:
Inspect the remaining margin after the valves are refaced. Valves with less than 1.190 mm (0.047 inch) margin should be discarded.
VALVE GUIDES
Measure valve stem guide clearance as follows:
Positioning Valve With Tool C-3973:
1. Install Valve Guide Sleeve Tool C-3973 over valve stem and install valve. The special sleeve places the valve at the correct height for checking with a dial indicator.
Measuring Valve Guide Wear:
2. Attach Dial Indicator Tool C-3339 to cylinder head and set it at right angle of valve stem being measured.
Reamer Sizes:
3. Move valve to and from the indicator. The total dial indicator reading should not exceed 0.432 mm (0.017 inch). Ream the guides for valves with over-size stems if dial indicator reading is excessive or if the stems are scuffed or scored.
Service valves with oversize stems are available.
Slowly turn reamer by hand and clean guide thoroughly before installing new valve. Ream the valve guides from standard to 0.381 mm (0.015 inch). Use a 2 step procedure so the valve guides are reamed true in relation to the valve seat:
^ Step 1-Ream to 0.0763 mm (0.003 inch).
^ Step 2-Ream to 0.381 mm (0.015 inch).
VALVE SEATS
Refacing Valve Seats:
CAUTION: DO NOT un-shroud valves during valve seat refacing.
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 a. 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 the top edge of valve face, lower valve seat, with a 15° stone. If the blue is transferred to bottom edge of valve face raise valve seat with a 60° stone.
4. When seat is properly positioned the width of intake seats should be 1.016-1.524 mm (0.040-0.060 inch). The width of the exhaust seats should be 1.524-2.032 mm (0.060-0.080 inch).
VALVE SPRING INSPECTION
Testing Valve Spring For Compression Length:
Whenever valves have been removed for inspection, reconditioning or replacement, valve springs should be tested. As an example the compression length of the spring to be tested is 1-5/16 inch. Turn table of Universal Valve Spring Tester Tool until surface is in line with the 1-5/16 inch mark on the threaded stud. Be sure the zero mark is to 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 2. 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.