Arizona republican., 1921-11-20

signs the guides may be sprung l slightly so that they will grip the liter more tightly and this remedies the trouble.
 Another possible location of noisy operation is at the cam, between which and the follower there may be l too much clearance. Fitting new followers usually takes care of this trouble. Worn valve stems or guides also produce noise. Removal of the springs will enable the operator to locate trouble at this point. There should be no side play of the stem in Its guide and if this condition is found to exist, bushings should be fitted in the guide, or else a new valve with an oversize stem should be installed.
 When the valve system is of the overhead type it is natural to look for more noise than in the conventional type- Adequate fabrication will do much to remedy this trouble with the overhead system Occasionally side play develops in the rocker arms with slap as result. A worn arm bear ing also will make trouble, and the cure in this case is to fit an oversize pushing in the rocker arm.
 While the valve system is the com monest seat of noise troubles in the Cii5iA4C IL IS A4OL lne SU1e lOCdllOii where this trouble may be looked for. The bearings in most engines are of soft metal, which must be kept copi- ously fabricated or it will burn and flatten out with a knock as the result. The ordinary remedy for this is to take up the bearing by removing the shim between the two halves, or else | to trim the metal on the movable part. Care must be used in perform ing this operation to see that the bearing touches the shaft all around without being too tight.
 1 In fitting bearings the utmost care must be exercised to see that the shaft Is not thrown out of alignment, and this condition is particularly like ! ly to result where one bearing is taken up without reference to the others. In unit power plant designs, when the shaft is thrown out of alignment, one of the shafts in the transmission is sure to bind and noisy operation is inevitable.
 Another source of bearing knocks is found in the flanges of the crank shaft bearings which are flattened by crankshaft thrust. In this case it | does not pay to try and fix the old bearing nanges; 1t is better simply to get a new bearing.
 Play often develops in the upper rod bearing and often enough the car owner planes the lower rod or crank shaft bearing. On many of the cheap CT cars there is no bearing at the tor of the rod, while in certain others 2 bronze pushing is installed to take up the wear. When there is no bush ing, new piston pin will have to be fitted, or if the piston bosses art worn eccentric it may mean a new Ipiston or the installation of bush ing.
 When the pistons or cylinders ar, worn the result is a knock tha sounds much like the one that come. from pre-ignition. If this trouble il not in an advanced stage 1t may b, cured by fitting new rings. On tn, other hand, a severe case may requir, the installation of a complete nev set of pistons. When the cylinder have worn slightly oval, the remed, is to rebore them in a larger size, fit ting new pistons. This gives prac
 tically new cylinder block.
 Timing gear noises are fairly com
 mon, in which class must be included
 chain noises. Some silent chains hav to wear, while others must be short
 ened by taking out a link. In tn
 case of chronic chain noise, the ca
 owner will do well to consult serv l ice station.
 One of the commonest knocks of al l Is that due to pre-ignition. This ma,
 be caused by carbon deposits in tn
 engine or by too great an advance o
 the spark. Poor timing will als
 cause the trouble. while overheatinl overlooking the engine and incorrec
 mixture are alternate causes. Tn result is always the same. The fut
 charge explodes too soon. not givin
 the piston time to reach top dea
 center and the result is a thrus
 against the side of the cylinder wal In curing pre-ignition knocks one ha
 to proceed by process of elimination
 beginning with carbon, which is tn
 coumonest cause.
 Transmission noises are not at a
 uncommon and generally result fror
 one of the shafts being out of line D
 reason of a worn bearing or a bind
 ing gear. Sometimes the entfi
 transmission is out of line, so tha