Effects Of Changes in Cam Timing and Lobe Separation Angle

Comp Cams logoThe following tables provided by COMP Cams illustrate how variations in lobe separation angle and cam timing affect engine behavior. Engine builders can refer to these characteristics often to determine the likely effect of any cam timing alterations they may contemplate. Knowing how these things affect engine operation can help you in the engine planning stages if you want to leave some tuning leeway in your cam selection. Our thanks to Comp Cams for providing this easy to use reference guide for our readers.

EFFECTS OF ALTERING CAMSHAFT TIMING

AdvancingRetarding
Begins Intake Event SoonerDelays Intake Closing Event
Opens Intake Valve EarlierKeeps Intake Valve Open Longer
Builds More Low-End TorqueBuilds More High-RPM Power
Decreases Piston-Intake Valve ClearanceIncreases Piston-Intake Valve Clearance
Increases Piston-Exhaust Valve ClearanceDecreases Piston-Exhaust Valve Clearance

EFFECTS OF CHANGING LOBE SEPERATION ANGLE (LSA)

Tighten (smaller LSA number)Widen (larger LSA number)
Moves Torque to Lower RPMRaise Torque to Higher RPM
Increases Maximum TorqueReduces Maximum Torque
Narrow Power bandBroadens Power Band
Builds Higher Cylinder PressureReduce Maximum Cylinder Pressure
Increase Chance of Engine KnockDecrease Chance of Engine Knock
Increase Cranking CompressionDecrease Cranking Compression
Increase Effective CompressionDecrease Effective Compression
Idle Vacuum is ReducedIdle Vacuum is Increased
Idle Quality SuffersIdle Quality Improves
Open Valve-Overlap IncreasesOpen Valve-Overlap Decreases
Closed Valve-Overlap IncreasesClosed Valve-Overlap Decreases
Natural EGR Effect IncreasesNatural EGR Effect is Reduced
Decreases Piston-to-Valve ClearanceIncreases Piston-to-Valve Clearance

CAMSHAFT GEOGRAPHY AND LOBE FUNCTION

1) Max Lift or Nose
2) Flank
3) Opening Clearance Ramp
4) Closing Clearance Ramp
5) Base Circle
6) Exhaust Opening Timing Figure
7) Exhaust Closing Timing Figure
8) Intake Opening Timing Figure
9) Intake Closing Timing Figure
10) Intake to Exhaust Lobe Separation
Lobe Separation Diagram