49. Valve Guide Reaming, and Valve and Seat Grinding
^ Tools Required- J 8001 Dial Indicator Set
1. Recondition the valve seats by grinding. Use an oscillating type valve seat grinder. Follow the grinder manufacturer's instructions. If the valve seat is too wide after grinding, use a 20 degree stone or a 70 degree stone in order to narrow the valve seat. The 20 degree stone will lower the seat. The 70 degree stone will raise the seat. Replace or recondition the valves if the seats are reconditioned.
2. After grinding the valves, measure the valve margin. Replace the valve if less than the minimum recommended specification.
Notice: Clean the valve guides before reaming. Packing of chips or carbon may result in the reamer jamming into the valve guide or broken reamer flutes.
3. Clean any foreign material from the valves. Use a wire brush to remove carbon. Do not scratch the valve stem. Soak the valves in carburetor cleaning fluid to remove varnish.
4. Use a suitable tool to clean the valve guides.
5. Follow the grinder manufacturer's instructions. Ensure that the new surface is perpendicular to the valve stem.
6. Inspect the valve key grooves for chipped or worn lands (5). Replace the valve if the valve key groove is damaged.
7. Inspect the valve stem tip for wear (6). Recondition the valve stem tip by grinding.
8. Inspect the valve stem for burrs and scratches (4). Use an oil stone to remove burrs and minor scratches.
9. Inspect the valve stem for straightness (3). Use V blocks to inspect the valve head for bending or distortion. Replace any bent or distorted valves.
10. Inspect the valve face for grooving (1, 2). If the groove is so deep that refacing the valve face would result in a knife edge, replace the valve.
11. Inspect the valve face for burning, pitting, or cracking (1, 2, 3, 4). If pieces of the valve face are broken off, inspect the corresponding piston and cylinder head area for damage.
12. Measure the valve movement:
12.1. Insert the valve into the guide.
12.2. Lift the valve 2 mm (1/8 inch) off of the seat.
12.3. Move the valve from side to side.
12.4. Use J 8001 to measure the amount of movement.
Important: Clean the valve guide before reaming to avoid breaking the reamer flutes. Do not push down on the reamer.
13. Ream the valve guides for oversize valves if the clearance exceeds the specifications.
14. Ream the valve guide bores for the oversize valves.
15. Recondition the valve seats after reaming the valve guide bores or installing the new valve guides.
16. Inspect the valve stem for straightness. Use V blocks to inspect the valve head for bending or distortion. Replace any bent or distorted valves.
^ It is essential that the valve guide bores are free of carbon or dirt to ensure the proper centering of the pilot in the guide. The valve seats should be concentric to within 0.05 mm (0.031 inch) total indicator reading.
^ Reface pitted valves on a valve refacing machine to ensure the correct relationship between the valve head and the valve stem. Replace the valve if the valve stem is warped (2), or if the valve stem shows signs of excessive wear.
Inspect the valve key area (1) for damage and carbon build up.
Replace the valve if the edge of the head is less than 0.79 mm (0.031 inch) thick after grinding.
^ Use the manufacturer's recommendations of equipment for the proper results.