follower fails to revolve and the cams wipe the sameINSPECTING AND REPAIRINGsurface each time the camshaft revolves.CAMSHAFTSNormal use will cause surface disintegration,usually as the hardened surfaces begin to fatigue. Thecondition is aggravated by abrasive particles. Nicks anddents on rollers will also cause disintegration.You must make constant checks for defective rollersor surfaces and for nicks, scratches, or dents in thecamshaft. Whenever you find a defective cam follower,you should replace it. In roller-type cam followers youmust replace a worn cam follower body and guide orroller needle bearings (if used).Defective or poorly operating valve adjusters allowclearance or lash in the valve gear. Noisy operation of alash adjuster indicates that there is insufficient oil in thecylinder of the unit. When you discover a noisy lashadjuster and the oil supply or pressure is not the sourceof trouble, remove and disassemble the unit accordingto the manufacturer’s instructions.Since the parts of lash adjusters are notinterchangeable, disassemble only one unit at a time.Check for resinous deposits, abrasive particles, a stuckball check valve, a scored check valve seat, andexcessive leakage. Carefully wash all parts of thehydraulic lash adjuster in kerosene or diesel fuel. Checksuch parts as the cam follower body, plunger or piston,and hydraulic cylinder for proper fit.Camshafts can be saved when the cams alone aredamaged, if the cams are of the individual type, sincesuch cams may be removed and replaced. Figure 3-17illustrates the method of removing an individual camfrom its shaft.When you remove a camshaft from an engine, cleanit thoroughly with either kerosene or diesel fuel. Aftercleaning the shaft, dry it with compressed air. Aftercleaning the cam and journal surfaces, inspect them forany signs of scoring, pitting, or other damage.When you remove or insert a camshaft through theend of the camshaft recess, rotate it slightly. Rotating thecamshaft allows it to enter easily and reduces thepossibility of damage to the cam lobes and bearings.After you visually inspect a camshaft, place it onV-blocks and measure the shaft runout by using a dialindicator. When you measure the runout, take theout-of-roundness into consideration. Compare yourmeasurements to the manufacturer’s specifications.Also, measure the camshaft bearing journals with amicrometer. Figure 3-18 illustrates a camshaft withbearing journals.A camshaft needs to be replaced if the followingconditions occur:1. The lobes are damaged, as lobes cannot berepaired.2 . R u n o u t e x c e e d s t h e m a n u f a c t u r e r ’ sspecifications.3. Wear on the shaft bearing journals exceeds themanufacturer’s specifications.4. The keyways are damaged.Figure 3-18.—Camshaft with bearing journals in a V-typeengine.Figure 3-17.—Removing an individual cam.3-13
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business