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

2. CHAPTER OBJECTIVES Explain the function of the valve train.
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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. CHAPTER OBJECTIVES Properly degree a camshaft.
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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. CHAPTER INTRODUCTION Internal combustion engine is a AIR PUMP.
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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. CAM DRIVES The Camshaft is Driven by the Crankshaft.
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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. CAM DRIVES Three types of cam drives. Timing chain and sprockets.
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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
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COMMON CAM DRIVES

8. GEAR DRIVES Cam gear is soft - Fiber or Aluminum Crank gear - Steel
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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. SPROCKETS Used with chains. Can be made of:
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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. TIMING CHAINS Roller Chain (bicycle style) Silent Chain - 2 styles
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TIMING CHAINS
Roller Chain (bicycle style)
Silent Chain - 2 styles
Small Pin - Stiff
Large Pin - Limp
Page 245

11. TIMING BELTS Cogged Belt Drive.
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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
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ECCENTRIC ADJUSTER

13. TIMING the CAM to the CRANK
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TIMING the CAM to 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. TIMING the CAM to the CRANK
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TIMING the CAM to 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. CAMSHAFT Two cam lobes per cylinder One lobe for the Intake Valve
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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. CAM THRUST Cam Gear provides thrust surface.
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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. PARTS of a CAM LOBE Base circle Lobe or Nose Opening and Closing Ramps
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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
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PARTS of a CAM LOBE
Page 247

19. CAM MEASUREMENTS Lift - Valve & Cam - Measured in inches.
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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
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CAM CARD
Page 243

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

22. OVERLAP and CENTERLINE
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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
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LOBE SEPARATION ANGLE
Page 254 Lab

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

25. LIFTER AND CAM LOBE Lifter face has Convex Shape.
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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. LIFTER AND CAM LOBE Lubrication and Break-in.
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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. LIFTER AND CAM LOBE Minimum RPM 1500 for 15 Minutes.
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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
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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. ROLLER CAM AND LIFTERS Roller Cams are made of steel (not cast iron).
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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. REGRINDING CAMS AND LIFTERS
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REGRINDING CAMS AND LIFTERS
I do not recommend using reground cams.
I do not recommend using reground lifters.
Page 259 Lab

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