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CHAPTER 10

CBC AUTOMOTIVE RK. CHAPTER 10. The Valve Train Classroom Manual Page 243 Lab Manual Page 245. CBC AUTOMOTIVE RK. CHAPTER OBJECTIVES. Explain the function of the valve train. Describe the automatic belt tensioners. List the components of the valve train.

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CHAPTER 10

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  1. CBC AUTOMOTIVE RK CHAPTER 10 • The Valve Train • Classroom Manual • Page 243 • Lab Manual • Page 245

  2. CBC AUTOMOTIVE RK CHAPTER OBJECTIVES • Explain the function of the valve train. • Describe the automatic belt tensioners. • List the components of the valve train. • Explain the purpose & function of the camshaft. • Describe the relationship between the camshaft lobe design and lift, duration and overlap.

  3. CBC AUTOMOTIVE RK CHAPTER OBJECTIVES • Properly degree a camshaft. • Explain the purpose of lifters. • Describe the operation of hydraulic lifters. • Inspect the pushrods & DNR. • Describe the methods used to correct rocker arms, and rocker arm geometry.

  4. CBC AUTOMOTIVE RK CHAPTER INTRODUCTION • Internal combustion engine is a AIR PUMP. • MORE AIR - MORE POWER. • Cam grind determines Performance. • Cam grind determines driveability characteristics. • Cam Drives Page 243

  5. CBC AUTOMOTIVE RK CAM DRIVES • The Camshaft is Driven by the Crankshaft. • Cam is driven at one half Crank speed. • Cam Gear has twice as many teeth as crank gear. Page 244 Class

  6. CBC AUTOMOTIVE RK CAM DRIVES • Three types of cam drives. • Timing chain and sprockets. • Some engines use spacers between sprocket and cam. • Gear drives. • Heat Aluminum Gears to aid installation. • Belt and sprockets. Page 244 Class

  7. CBC AUTOMOTIVE RK COMMON CAM DRIVES

  8. CBC AUTOMOTIVE RK GEAR DRIVES • Cam gear is soft - Fiber or Aluminum • Are press fit to cam - Pre-heat to 200 degrees to install. • Crank gear - Steel • Advantages - Less wear and Backlash • Disadvantages - Takes more space and can be noisy. Page 245

  9. CBC AUTOMOTIVE RK SPROCKETS • Used with chains. • Can be made of: • Steel • Iron • Aluminum (Nylon coated teeth) - can stick oil pump relief valve. • Do Not use a worn Sprocket with a New Chain. Page 245

  10. CBC AUTOMOTIVE RK TIMING CHAINS • Roller Chain (bicycle style) • Silent Chain - 2 styles • Small Pin - Stiff • Large Pin - Limp Page 245

  11. CBC AUTOMOTIVE RK TIMING BELTS • Cogged Belt Drive. • Advantages Lighter, Quieter, Easier to Change. • Virtually no stretch in service. • Watch rib tooth shape - Rounded or Square. • Replacement 30,000 to 60,000 miles. Page 245

  12. CBC AUTOMOTIVE RK ECCENTRIC ADJUSTER

  13. CBC AUTOMOTIVE RK TIMING the CAMto the CRANK • Timing marks facing each other. • Timing marks a specified number of links apart. • Timing marks aligned with colored links on the chain. • Timing marks align with marks on head and block. Page 247 Lab

  14. CBC AUTOMOTIVE RK TIMING the CAMto the CRANK • Match old parts to new ones. • Specifically match keyway and timing mark. • Make sure # 1 piston is at TDC when marks are lined up. • Off brands are noted for inaccurate timing marks. Page 248 Lab

  15. CBC AUTOMOTIVE RK CAMSHAFT • Two cam lobes per cylinder • One lobe for the Intake Valve • One for the Exhaust Valve • High Performance Multi-Valve per Cylinder Engines • One lobe per valve 4 on 4 valve per cylinder • Fuel Pump Eccentric cast-in or bolted on • Distributor and Oil Pump Drive Gear

  16. CBC AUTOMOTIVE RK CAM THRUST • Cam Gear provides thrust surface. • Oil pump driven by bottom of distributor shaft. • Lifters also provide thrust. • Timing Chain. • Some Engines have a thrust plate. Lecture

  17. CBC AUTOMOTIVE RK PARTS of a CAM LOBE • Base circle • Lobe or Nose • Opening and Closing Ramps • Opening and Closing Clearance Ramp • Page 194 Figure 8.22 Page 245

  18. CBC AUTOMOTIVE RK PARTS of a CAM LOBE Page 247

  19. CBC AUTOMOTIVE RK CAM MEASUREMENTS • Lift - Valve & Cam - Measured in inches. • Duration - Measured in degrees of crank rotation. • Overlap - Both intake & exhaust valves open. • Split Overlap - Both valves open equally at TDC. • Centerline - Point of maximum opening. Page 248

  20. CBC AUTOMOTIVE RK CAM CARD Page 243

  21. CBC AUTOMOTIVE RK CAM PATTERNS • Single pattern - Intake and Exhaust lobes have same Profile. • Asymmetrical - Intake and Exhaust Profiles are different. Page 248

  22. CBC AUTOMOTIVE RK OVERLAP and CENTERLINE • Lobe spread 105 to 115 degrees. • Advanced cam timing - Intake centerline less than lobe spread. • Advanced cam timing improves low and mid range Torque. • Retarded cam timing - Intake centerline greater than lobe spread. • Retarded cam timing improves high RPM power. Page 248

  23. CBC AUTOMOTIVE RK LOBE SEPARATION ANGLE Page 254 Lab

  24. CBC AUTOMOTIVE RK VALVE LIFTERS • Mechanical • Hydraulic • Flat Tappet • Mushroom • Roller Page 250

  25. CBC AUTOMOTIVE RK LIFTER AND CAM LOBE • Lifter face has Convex Shape. • Cam Lobe has taper of .0007” to .002”. • Lifter must spin to Dissipate Load. • Lifter’s convex shape prevents Edge Loading. Page 249

  26. LIFTER AND CAM LOBE • Cam and Lifters become wear mated in first few minutes. • If cam is replaced replace lifters also. • Used lifters will rapidly wear out a new cam. Page 249

  27. CBC AUTOMOTIVE RK LIFTER AND CAM LOBE • Lubrication and Break-in. • Cam is lubed by crank spray • First 1/2 Hour is Critical. • Must use (EP) Extreme Pressure Lubricant. Page 249

  28. CBC AUTOMOTIVE RK LIFTER AND CAM LOBE • Minimum RPM 1500 for 15 Minutes. • Some OHV have oil passage in cam. • Oil holes on each Lobe, if plugged instant cam failure. • Oil changes are important to cam life. • Page 194 Figure 8.21 Page 249

  29. CBC AUTOMOTIVE RK ROLLER CAM AND LIFTERS • Roller lifters can accept higher lift rate without wear. • Roller lifters reduce valve train friction. • Roller lifters must have a way of keeping them from turning. Page 250

  30. CBC AUTOMOTIVE RK ROLLER CAM AND LIFTERS • Roller Cams are made of steel (not cast iron). • Roller Cams have more aggressive Profiles. • Lobes are polished to a fine matte finish. • After break-in, the lobe has a mirror finish. Page 245

  31. CBC AUTOMOTIVE RK REGRINDING CAMSAND LIFTERS • I do not recommend using reground cams. • I do not recommend using reground lifters. Page 259 Lab

  32. CBC AUTOMOTIVE RK VALVE LASH • Mechanical Camshafts • Hydraulic Camshafts • Clearance Page 263 Lab

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