Pine Bluff daily graphic., 1919-08-31
BE SURE SPARK OCCURS AT THE
 RIGHT MOMENT
Too Early Ignition Strains the Engine and Too Late Wastes
 Fuel,


 Fuel,
 It is of the utmost importance that the spark should occur in each cylin- der, when it's piston is at exactly the correct point in it's stroke. The lg- milton timer (make-and- break device or distributor), which determines the instant at which the sparks occur, lis operated from the same shaft that operates the valves (the cam shaft, and runs one-half as fast as the en- zine itself. The timing decise itself is a cam or small lobed wheel, usu- ally mounted upon and driven from the upper end of a vertical shaft, and the number of lobes or equally space projections on the cam is the same as the number of cylinders. Each time that each of these projections makes a revolution it forces apart the breaker contacts-a pair of platinum or tungsten points-thus breaking the battery circuit and causing spark in each cylinder once every two revolutions. It is the instant at which these breaker contacts are ! separated that determines the tim- ing of the spark and this must coin eide exactly with the instant when the piston is at the point at which the spark is required The ignition cam is not permanently fastened up on it's driving shaft, but may be loos- ened and turned upon it, and the tim ing thus made earlier or later. It the cam is turned upon it's shaft in the same direction that the shaft runs, the cam projections open the lcontacts later in the revolution, when the piston is further along in it's movement and, if the cam is turned oppositely to the direction of shaft motion, the sparks occur at an earlier phase of the piston movement. Mov- ing the spark lever has the same ef- feet as slightly retarding or advanc- ing the cam on it's shaft, with cor responding change in the piston DO sition at which sparks occur. The ignition cam is supposed to be adjust ed at the factory, so that as much adjustment of spark position, as will Ibe required, can be obtained by nov ling the spark lever, but it often hap pens that this setting is not correct or that the adjustment changes, With ! the result that the spark lever can not be set in such position as to give good results under all conditions "A change of the setting of the igni- ltion cam is then required. To ascer- tain whether the spark is set correct |ly it is necessary to know the posi- |tion of the pistons and to observe the action of the breaker points.
 Timing the Ignition
 In checking up the ignition timing lit is necessary to know when the piston of the cylinder whose timing lis being verified is at the top of its stroke. Most engines have this po- sition marked upon flywheel. In the case of -four" there are usually two marks DC and and DC and 8 or equivalent inscriptions, that ln- dicate when the cylinders thus num- bered are on upper dead center, that is with their pistons at top stDke In the case of six, there are three markings each giving upper dead Icenter for two cylinders. If an engine has no flywheel markings and . pointer, there is usually a plug in each cylinder head that can be re- moved and through which wire can f be run to touch the piston head. By 'cranking the engine over slowly, with l the wire in place, the highest posi- tion of any piston can readily be de- j termined. The spark should always occur in any cylinder when it's piston . is approximately fully up on it's com pression stroke and the fact that it is l on compression is indicated by both l it's valves being closed, that is, with their push rods free of them. Differ , ent engines and ignition systems cal. l; for somewhat different ignition set tings and in the instruction book will be found exact directions, but the fol- l lowing is a setting that may safely l be used in a majority of cases: Place , the spark lever in it's most retarded position, turn the engine over until cylinder, say number one, is on com pression and it's piston is exactly on l top dead center-taking out all spark plugs will facilitate accurate setting. , The breaker points should then just ; be beginning to be separated by the cam and, if this is the case, no ad justment of the cam need be made, but if it is not, the cam should be loosened upon it's shaft and turned one way or the other, just enough so that the points are barely starting to open. Before changing the cam set ting, however, the points should be adjusted-if they require it-so that they separate the correct distance, , which is usually about 0.2 inch, for ; if this is not done, one cannot be cer
 tain that the cam requires resetting. There is usually some lost motion in the gearing which drives the timer and this should be taken up in the di
 rection the timer runs before per manent setting is made, as other wise the adjustment will be in error. The high tension arm of the distri
 butor should be touching the point to , which number one spark-plug cable is attached.
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