General Camshaft Information

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76FleetBrougham

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Found this on another forum while searching for some info.  might be useful for people to visualize their cam setup:

And a link to the same information at compcams:
http://www.compcams.com/Technical/FAQ/LSAproperties.asp

Effects of Altering Camshaft Timing

Advancing                                   Retarding

Begins Intake Event Sooner                    Delays Intake Closing Event
Open Intake Valve Sooner                      Keeps Intake Valve Open Later
Builds More Low-End Torque                   Builds More High-RPM Power
Decrease Piston-Intake Valve Clearance   Increase Piston-Intake Valve Clearance
Increase Piston-Exhaust Valve Clearance  Decrease Piston-Exhaust Valve Clearance



EFFECTS OF CHANGING LOBE SEPERATION ANGLE (LSA)

Tighten (smaller LSA number)        Widen (larger LSA number)

Moves Torque to Lower RPM                Raise Torque to Higher RPM
Increases Maximum Torque                 Reduces Maximum Torque
Narrow Power band                            Broadens Power Band
Builds Higher Cylinder Pressure              Reduce Maximum Cylinder Pressure
Increase Chance of Engine Knock          Decrease Chance of Engine Knock
Increase Cranking Compression             Decrease Cranking Compression
Increase Effective Compression             Decrease Effective Compression
Idle Vacuum is Reduced                       Idle Vacuum is Increased
Idle Quality Suffers (lopy)                    Idle Quality Improves (smooth)
Open Valve-Overlap Increases               Open Valve-Overlap Decreases
Closed Valve-Overlap Increases             Closed Valve-Overlap Decreases
Natural EGR Effect Increases                 Natural EGR Effect is Reduced
Decreases Piston-to-Valve Clearance      Increases Piston-to-Valve Clearance




LOBE SEPARATION ANGLE
Above 114 Deg. = Extremely Wide
114-112 Deg. = Wide
112-110 Deg. = Moderately Wide
110-108 Deg. = Moderate
108-106 Deg. = Moderately Tight
106-104 Deg. = Tight
Below 104 Deg. = Extremely Tight




Always wondered about LSA.  now i know!  :D

Blake
 
I thought that tighter LSA results in less cranking compression due to more overlap, and thus it should be less propane to detonation?
 
shiftless said:
I thought that tighter LSA results in less cranking compression due to more overlap, and thus it should be less propane to detonation?
Click to expand...


Same here. But, what do I know? Somebody enlighten me.

d
 
I know the 108 degrees of lobe seperation on my Lunati cam made the 472 in my Fiat Topolino think it's a Fuel Altered.  I wouldn't change a thing. 
Jackie
 
shiftless said:
I thought that tighter LSA results in less cranking compression due to more overlap, and thus it should be less propane to detonation?
Click to expand...

      Tighter LSA effectively advances intake closing,so at cranking speeds where the engine is not yet producing exhaust gases the cylinder pressure is higher.Once the engine is running and producing exh gas the "natural EGR effect" of contaminated intake charge due to overlap will lower cyl pressure and help prevent low-speed detonation.However,in the mid-range where the torque quickly peaks with a tight LSA,the added cyl pressure will encourage detonation if the duration of the grind is not high enough to make peak torque occur at a fairly high engine speed.

  Terry
 
Plus overlap is not during the compression stroke,it's between the exhuast and intake events, so no cylinder pressure gets bled off, so it's all about the intake closing event.
 
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