130
from the engine base to provide access to the valve heads which are inside of that member, and which cannot be reached from the outside, as is true of the L or T-cylinder construction.
The preferred method of carrying the valves when they are placed in the cylin- der head in the Buick 6-cylinder motor, is shown in Fig. lo. The valves are carried in cages which are readily re- moved from the cylinder head by un- screwing the retention nut that keeps the valve cage tightly pressed against the seating at its lower end to ob- tain a gas-tight joint. The valve cages are easy to handle and it is a relatively simple operation to compress the valve spring and remove the pin which makes for easy removal of the valve. When this construction is followed it is possible to grind in the valve by simply removing the cage assemblies from the cylinder. It is not necessary to disturb the cylinder in any way and does not call for disconnection of intake or ex- haust manifolds ; the only things that need be removed are the valve operating tappets, which is work of but a few mo- ments.
Valve GrhiSng Process
Much has been said relative to valve grinding, and despite the mass of in- formation given in the trade prints it is rather amusing to watch the average re- pairman or the motorist who prides him- self on maintaining his own car perform- ing this essential operation. The com- mon mistakes are attempting to seat a badly grooved or pitted valve head on an equally bad seat, which is an almost hopeless job, and of using coarse emery and bearing down with all one's weight on the grinding tool with the hope of quickly wearing away the rough sur- faces. The use of improper abrasive ma- terial is a fertile cause of failure to ob- tain a satisfactory seating. Valve grind- ing is not a difficult operation if certain precautions are taken before undertaking the work. The most important of these is to ascertain if the valve head or seat is badly scored or pitted. If such is found to be the cause no ordinary amount of grinding will serve to restore the surfaces, in this event the best thing to do is to remove the valve from its seat-
��Popular Science Monthly
ing and to smooth down both the valve head and the seat in the cylinder before attempt is made to fit them together by grinding. Another important precaution is to make sure that the valve stem is straight, and that the head is not warped out of shape or loose on the stem when the valve is a two-piece member.
Valve Grinding Processes
Alention has been previously made of the importance of truing both valve head and seat before attempt is made to refit the parts by grinding. The appearance of a valve head when pitted or scored is indicated at Fig. ii, A, in order that the motorist or novice repairman can readily identify this defective condition. After smoothing the valve seat the next step is to find some way of turning the valve. Valve heads are usually provided with a screw driver slot passing through the boss at the top of the valve or with two drilled holes to take a forked grind- ing tool. The method of arranging the valve head for the grinding tool and the types of grinding tools commonly used are also shown at Fig. ii, A. A combi- nation grinding tool which may be used when either the two drilled holes or the slotted head form of valve is to be ro- tated is shown at Fig. ii, B. This con- sists of a special form of screw driver having an enarged boss just above the blade, this boss serving to support a U- shaped piece which can be securely held in operative position by the clamp screw or which can be turned out of the way if the screw driver blade is to be used.
As it is desirable to turn the valve through a portion of a revolution and back again rather than turning it always in the same direction, a number of spe- cial tools has been designed to make this oscillating motion possible without trou- ble. A simple valve grinding tool is shown at Fig. ii, C. This consists of a screw driver blade mounted in a handle in such a way that the end may turn freely in the handle. A pinion is secure- ly fastened to the screw driver blade shank, and is adapted to fit a rack pro- vided with a wood handle and guided by a bent bearing member securely fast- ened to the screw driver handle. As the rack is pushed back and forth the pinion
�� �
