Valve: Service and Repair
VALVE AND VALVE SEAT - REFACING
The valve face and valve seat angles are shown in (Fig. 40).
Inspect the remaining margin after the valves are refaced.
VALVE SEATS
CAUTION: Do not un-shroud valves during valve seat refacing (Fig. 41).
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 top edge of valve face, lower valve seat with a 30 degree stone. If the blue is transferred to the bottom edge of valve face raise valve seat with a 75 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 both seats should be 1.02 - 1.52 mm (0.040 - 0.060 inch) (Fig. 40).
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) and valve spring installed height (B) (Fig. 42). If valve tip height is greater than 49.53 mm (1 61/64 inch) grind valve tip until within specifications. Make sure measurements is taken from cylinder head surface to the top of valve stem.
3. Install valve spring seats over valve guides and new seals on all valve stems (Fig. 43). 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. 42), make sure measurements are taken from top of spring seat to the bottom surface of spring retainer. If height is greater than 42.65 mm (1.670 inch), install a 0.794 mm (1/32 inch) spacer in head counter-bore under the valve spring seat to bring spring height back to 41.85 - 43.44 mm (1.648 - 1.710 inch).
INSPECTION
Valve
1. Clean valves thoroughly and discard any burned, bent, warped, and cracked valves.
2. Measure valve stems for wear.
NOTE: Valve stems are chrome plated and should not be polished.
Valve Guide
1. Remove carbon and varnish deposits from inside of valve guides with a reliable guide cleaner.
2. Measure valve stem guide clearance as follows:
3. 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.
4. Attach Special Tool C-3339, dial indicator to cylinder head and set it at right angle of valve stem being measured (Fig. 44).
5. Move valve to and from the indicator. If guides are out of specifications, ream to next oversize.
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) and 0.40 mm (0.015 inch) oversize.
NOTE: Oversize seals must be used with oversize valves.
a. Select the correct size reamer to accommodate the oversize valve stem. Refer to Valve Guide Oversize Chart.
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 0.40 mm (0.015 inch). Use a step procedure of 0.15 mm (0.005 inch) to 0.40 mm (0.015 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.
NOTE: Replace cylinder head if guide does not clean up with 0.40 mm (0.015 inch) oversize reamer, or if guide is loose in cylinder head.
VALVE GUIDE OVERSIZE CHART