Department of automobile engineering

Before they can be inspected, the valves must be cleaned. Due to the high temperatures in which they operate, any material that contacts the valve(oil, gas, carbon, etc.) will bake onto its surface.

Ordinary cleaning solvents may not be sufficient to remove this residue completely.

The best way to clean a valve is with a wire brush. A wire wheel mounted to a bench grinder is an even better alternative because it does the job much more quickly and easily. After you have cleaned the valves with a wire brush, wash them in cleaning solvent to remove lingering dirt particles. When the valves are clean, they can then be visually inspected.

If you inspect the valves and find them in satisfactory condition, they can be reused. Valves will experience some degree of wear and distortion from routine engine operation. Before you reuse a valve, its face should be reconditioned to give it a smooth, uniform appearance.

Usually a valve face will be ground to match a seat angle of 45 degrees; however some older engines may require a steeper valve and seat angle, say 60 degrees or So. After the grinding machine has been adjusted to produce the proper face angle, the valve should be inserted into the machine chuck and securely tightened. Turning on the machine will begin spinning the valve. Check to see that, as it spins, the valve head does not wobble. If you detect a wobbling head, first check the tightness of the chuck. If the chuck was tight and yet the valve continues to wobble, the valve itself must be bent and therefore should not be reused. A valve can be bent by debris inside an engine, or it can be warped by excess amounts of engine heat. In either case, the valve should be replaced.

The valve grinding machine will require grinding oil to lubricate its wheel as grinding occurs. A pump is used to spread oil onto the rotating grinding wheel. When you switch on the grinding machine, check to be sure that its oil pump is operating effectively. If you use a grinding machine absent proper lubrication, the valve face will be ground improperly. Grinding the valve face: when the machine is adjusted and the valve clamped into place, you can begin the process of grinding the valve face. Remember to wear safety glasses whenever you are using a grinding wheel. Move the valve face into light contact with the grinding wheel. Grind lightly, moving the spinning valve back and forth across the wheel until the grinding sounds smooth and uniform across the entire valve face surface.

When you first begin to grind, the valve surface will not be smooth and thus the grinding sounds will be sporadic and herky jerky. When the sound is uniform, you know that the wheel surface has begun to contact the valve face around its entire circumference. Move the valve away from the wheel, and check the face to see if its surface appears to be as uniform as the grinding wheel implied.