Valve Guide Reaming/Valve and Seat Grinding

1. Measure the valve stem-to-guide clearance.
2. Inspect the valve stems for excessive scoring, wear or bending.
^ Excessive valve stem-to guide clearance may cause a noisy valve train, premature valve stem oil seal wear, component damage, and/or excessive engine oil consumption.
^ Insufficient valve stem-to-guide clearance will result in noisy or sticking valves. Valves that are too tight may disturb engine smoothness or lead to component damage.





3. Ream the valve guides if necessary.

IMPORTANT: Carefully follow the manufacturers instructions when using valve guide reaming tools.

4. Valves are available in standard and in 1 mm oversize.





5. Ream the valve guide to obtain the proper stem-to-guide clearance.





IMPORTANT: Reconditioning the valve seats is very important. The seating of the valves must be perfect for the engine to deliver optimum power and performance. Another important factor is the cooling of the valve head. Good contact between the valve and the seat will ensure that heat will be properly dissipated. Several different types of equipment are available for grinding valve seats. The recommendations of the manufacturer of the equipment should be followed carefully to obtain the proper results. Regardless of what type of equipment is used, it is essential that valve guide bores be free from carbon or dirt to ensure proper centering of the tool pilot in the guide.

IMPORTANT: Valves that are pitted must be refaced to the proper angle. Valve stems that show excessive wear, or valves that are warped excessively must be replaced. When a valve head that is warped excessively is refaced, a knife edge may be ground on part or all of the valve head due to the amount of metal that must be removed. Knife edges lead to breakage, burning or pre-ignition due to heat localizing on this knife edge. If the edge of the valve head is less than 0.80 mm (0.031 inch) after grinding, replace the valve. Several different types of equipment are available for refacing valves. The recommendation of the manufacturer of the equipment should be carefully followed to obtain the proper results.

6. Inspect the valve for the following:
^ Burnt or eroded areas (1)
^ A worn margin (2)
^ A bent stem (3)
^ A worn or scored stem (4)
^ A worn key groove (5)
^ A worn stem tip (6)





7. Inspect the valve face for the following:
^ Worn or no margin (1, 4)
^ Pitted surfaces (2)
^ Burnt or eroded areas (3)





8. Inspect the valve margin.
The exhaust valve may be refaced if the margin is greater than 1.25 mm (0.050 inch) thick before grinding.
9. Reface pitted exhaust valves on a suitable valve refacing machine.
10. Replace the valve if the margin is less than 0.80 mm (0.031 inch) thick after grinding.
11. If the valve face has been ground, it may be necessary to shim the valve spring to obtain the proper spring installed height.





IMPORTANT: Excessive valve stem-to guide clearance may cause a noisy valve train, premature valve stem oil seal wear, component damage, and/or excessive engine oil consumption.
Insufficient valve stem-to-guide clearance will result in noisy or sticking valves. Valves that are too tight may disturb engine smoothness or lead to component damage.

12. Inspect for excessive valve stem (1) to guide (2) clearance.





13. Measure the valve stem-to-guide clearance.
14. A valve guide bore that is oversized must be repaired or replaced prior to valve seat grinding.
15. Inspect for a loose valve seat in the cylinder head. The valve seat has an interference fit to the cylinder head.
16. Clean the valve guide bores with a suitable tool. Remove all carbon or dirt from the bores.
The valve guide must be clean for the seat grinding tool to obtain proper results.
17. The valve seats should be concentric to within 0.05 mm (0.0021 inch) total indicator reading.
18. If the valve seat has be ground, it may be necessary to shim the valve spring in order to obtain the proper spring installed height.