How to choose a camshaft

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(Wider LSA:)
(Lobe intensity)
 
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====Narrower LSA:====
 
====Narrower LSA:====
A narrower LSA will ''increase'' overlap.  This has a tendency to reduce engine output at lower RPM and increase engine output at higher RPM.  A narrower LSA tend to make more peak power but a little less average power.  
+
A narrower LSA will ''increase'' overlap.  This has a tendency to increase engine output at lower RPM and decrease engine output at higher RPM.  A narrower LSA tend to make less peak power but more average power.  
 
*Moves torque to lower RPM
 
*Moves torque to lower RPM
 
*Increases maximum torque
 
*Increases maximum torque
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===Lobe intensity===
 
===Lobe intensity===
One more point about the cam profile is lobe intensity. For a given duration, more lift means the lobe ramps (the opening and closing faces on the sides of the lobe) are steeper (more intensity). That is to say, the cam lobe has has to accelerate the lifter faster to get to the peak lift within the available amount of duration duration. Faster ramp speed can give more "area under the curve", which usually equates to a broader, less peaky powerband. The downside for flat tappet cams is that the steeper ramps mean they contact the lifter at a greater angle, so the potential for wiping out a cam lobe or lifter is greater. Manufacturers are well aware of this, so they try to design the lobe profiles to optimize power, yet maintain good durability. Cam profiles like the Comp Cams XE-series and Lunati's Voodoo line are both at the edge of how fast the valve can be safely opened and closed. That's why they caution against using a higher ratio rocker arm when using these grinds. More on lobe intensity can be seen [http://www.harveycrane.com/duration.htm '''at this page'''] by Harvey Crane of Crane Cams.
+
One more point about the cam profile is lobe intensity. For a given duration, more lift means the lobe ramps (the opening and closing faces on the sides of the lobe) are steeper (more intensity). That is to say, the cam lobe has to accelerate the lifter faster to get to the peak lift within the available amount of duration duration. Faster ramp speed can give more "area under the curve", which usually equates to a broader, less peaky powerband. The downside for flat tappet cams is that the steeper ramps mean they contact the lifter at a greater angle, so the potential for wiping out a cam lobe or lifter is greater. Manufacturers are well aware of this, so they try to design the lobe profiles to optimize power, yet maintain good durability. Cam profiles like the Comp Cams XE-series and Lunati's Voodoo line are both at the edge of how fast the valve can be safely opened and closed. That's why they caution against using a higher ratio rocker arm when using these grinds. More on lobe intensity can be seen [http://www.harveycrane.com/duration.htm '''at this page'''] by Harvey Crane of Crane Cams.
  
 
===Intake centerline (ICL)===  
 
===Intake centerline (ICL)===  

Latest revision as of 10:47, 24 May 2020

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