How to choose a camshaft

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=== What do all the numbers mean? ===

----

−

'''Duration.'''

+

'''Duration:'''

This is the amount of time (stated in crankshaft degrees) that the cam will hold the valve off the seat. Some cams have the same duration for the intake and exhaust valves. They are typically called single pattern cams. Those with different numbers for intake and exhaust are often called split pattern or dual pattern. The design is ground into the cam and can't be altered without physically changing the camshaft lobe profiles.

−

'''Lift.'''

+

'''Lift:''

This is how far the lobe of the cam will push the lifter in a linear distance. It is measured by subtracting the base circle radius (or diameter) from the radius (or diameter) at the tallest point. This number is also ground into the cam, however the actual lift seen at the valve will change with rocker arm ratio.

[[http://www.tpub.com/content/constructiongrader/TM-5-3805-263-14P-2/img/TM-5-3805-263-14P-2_71_1.jpg]]

−

'''LSA'''

+

'''LSA:'''

Lobe Separation Angle, sometimes called Lobe Center Angle or Lobe Displacement Angle. This is a measurement in ''camshaft'' degrees that tells you how far apart the centerlines, or maximum lift points of the exhaust and intake lobes are. This number is ground into the cam and can't be altered without physically changing the camshaft lobe profiles.

[[http://www.lunaticamshafts.com/Images/Tech/Cams/LobeSeparationSmall.gif]]

−

'''Overlap'''

+

'''Overlap:'''

This number (usually not found on the cam card) represents the amount of duration in camshaft degrees when both the exhaust and intake valves are open at the same time. This factor is ground into the cam and can't be changed without physically altering the camshaft lobe profiles. Increasing duration at the same LSA will increase overlap. Decreasing LSA at the same duration will also increase overlap.

−

'''Intake and Exhaust Centerlines'''

+

'''Intake and Exhaust Centerlines:'''

−

Intake Centerline. This number represents where the intake lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the intake lobe and is measured in ''crankshaft'' degrees. A cam ground "straight up" will mean that the exhaust lobe's peak lift will happen at the same amount of degrees before top dead center, as the intake valve will peak after top dead center. ICL is machined into the cam. When cam manufacturers machine the snout of the cam for the cam sprocket, they will drill the holes with the cam slightly advanced, retarded, or straight up. When installed with stock components, the ICL can't be altered. Aftermarket timing chains and sprockets often have provisions for altering how the sprocket attaches to the cam and therefore you can counteract the ICL ground into the cam. If the LSA value is the same as ICL, the cam is ground "straight up." If the ICL is less than the LSA, it is ground advanced by the difference. If ICL is more than the LSA, the cam is ground retarded. For instance, if the cam has a 110-degree LSA with a 106 ICL, the cam is advanced by 4 degrees.

+

−

+

−

Exhaust Centerline. This number represents where the exhaust lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the exhaust lobe and is measure in crankshaft degrees.

+

−

+

−

~~'''Phasing the camshaft'''~~

+

−

While is is true that you cannot change the lobes of a camshaft after it is ground (unless you re-grind the lobes), you can alter the characteristics of the camshaft in your motor by installing it in either a retarded or advanced position relative to the crankshaft rotation. For instance, the manufacturer recommends the camshaft to be installed straight up, neither advanced or retarded from his design. However, you have determined that you are making too much horsepower down low and can't hook the tires up. You want to trade off a little of the lower end power for some higher end power. You might, in this case, install the camshaft slightly retarded. Although all four events (intake open, intake close, exhaust open, exhaust close) will be affected by changing the camshaft timing, the most important one will be the intake closing point. If you retard the camshaft, you will be closing the intake later, thus bleeding off some of the cylinder pressure and resulting in less low end power. Vice versa if you advance the camshaft. More bottom end, less top end.

+

Intake Centerline:

+

*This number represents where the intake lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the intake lobe and is measured in ''crankshaft'' degrees. A cam ground "straight up" will mean that the exhaust lobe's peak lift will happen at the same amount of degrees before top dead center, as the intake valve will peak after top dead center. ICL is machined into the cam. When cam manufacturers machine the snout of the cam for the cam sprocket, they will drill the holes with the cam slightly advanced, retarded, or straight up. When installed with stock components, the ICL can't be altered. Aftermarket timing chains and sprockets often have provisions for altering how the sprocket attaches to the cam and therefore you can counteract the ICL ground into the cam. If the LSA value is the same as ICL, the cam is ground "straight up." If the ICL is less than the LSA, it is ground advanced by the difference. If ICL is more than the LSA, the cam is ground retarded. For instance, if the cam has a 110-degree LSA with a 106 ICL, the cam is advanced by 4 degrees.

+

Exhaust Centerline:

+

*This number represents where the exhaust lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the exhaust lobe and is measure in crankshaft degrees.

+

'''Phasing the camshaft:'''

+

While is is true that you cannot change the lobes of a camshaft after it is ground (unless you re-grind the lobes), you can alter the characteristics of the camshaft in your motor by installing it in either a retarded or advanced position relative to the crankshaft rotation. For instance, the manufacturer recommends the camshaft to be installed straight up, neither advanced or retarded from his design. However, you have determined that you are making too much horsepower down low and can't hook the tires up. You want to trade off a little of the lower end power for some higher end power. You might, in this case, install the camshaft slightly retarded. Although all four events (intake open, intake close, exhaust open, exhaust close) will be affected by changing the camshaft timing, the most important one will be the intake closing point. If you retard the camshaft, you will be closing the intake later, thus bleeding off some of the cylinder pressure and resulting in less low end power. Vice versa if you advance the camshaft. More bottom end, less top end.

== How does all of that affect my engine's power? ==

How to choose a camshaft

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@@ Line 13: / Line 13: @@
 === What do all the numbers mean? ===
 ----
-'''Duration.'''
+'''Duration:'''
 This is the amount of time (stated in crankshaft degrees) that the cam will hold the valve off the seat.  Some cams have the same duration for the intake and exhaust valves. They are typically called single pattern cams. Those with different numbers for intake and exhaust are often called split pattern or dual pattern.  The design is ground into the cam and can't be altered without physically changing the camshaft lobe profiles.
-'''Lift.'''
+'''Lift:''
 This is how far the lobe of the cam will push the lifter in a linear distance.  It is measured by subtracting the base circle radius (or diameter) from the radius (or diameter) at the tallest point.  This number is also ground into the cam, however the actual lift seen at the valve will change with rocker arm ratio.
 [[http://www.tpub.com/content/constructiongrader/TM-5-3805-263-14P-2/img/TM-5-3805-263-14P-2_71_1.jpg]]
-'''LSA'''
+'''LSA:'''
 Lobe Separation Angle, sometimes called Lobe Center Angle or Lobe Displacement Angle. This is a measurement in ''camshaft'' degrees that tells you how far apart the centerlines, or maximum lift points of the exhaust and intake lobes are.  This number is ground into the cam and can't be altered without physically changing the camshaft lobe profiles.
 [[http://www.lunaticamshafts.com/Images/Tech/Cams/LobeSeparationSmall.gif]]
-'''Overlap'''
+'''Overlap:'''
 This number (usually not found on the cam card) represents the amount of duration in camshaft degrees when both the exhaust and intake valves are open at the same time.  This factor is ground into the cam and can't be changed without physically altering the camshaft lobe profiles.  Increasing duration at the same LSA will increase overlap.  Decreasing LSA at the same duration will also increase overlap.
-'''Intake and Exhaust Centerlines'''
+'''Intake and Exhaust Centerlines:'''
-Intake Centerline. This number represents where the intake lobe's peak lift occurs in relation to crankshaft rotation.  It is the point of maximum lift of the intake lobe and is measured in ''crankshaft'' degrees.  A cam ground "straight up" will mean that the exhaust lobe's peak lift will happen at the same amount of degrees before top dead center, as the intake valve will peak after top dead center.  ICL is machined into the cam.  When cam manufacturers machine the snout of the cam for the cam sprocket, they will drill the holes with the cam slightly advanced, retarded, or straight up.  When installed with stock components, the ICL can't be altered.  Aftermarket timing chains and sprockets often have provisions for altering how the sprocket attaches to the cam and therefore you can counteract the ICL ground into the cam.  If the LSA value is the same as ICL, the cam is ground "straight up."  If the ICL is less than the LSA, it is ground advanced by the difference.  If ICL is more than the LSA, the cam is ground retarded.  For instance, if the cam has a 110-degree LSA with a 106 ICL, the cam is advanced by 4 degrees.
-Exhaust Centerline. This number represents where the exhaust lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the exhaust lobe and is measure in crankshaft degrees.
-'''Phasing the camshaft'''
-While is is true that you cannot change the lobes of a camshaft after it is ground (unless you re-grind the lobes), you can alter the characteristics of the camshaft in your motor by installing it in either a retarded or advanced position relative to the crankshaft rotation. For instance, the manufacturer recommends the camshaft to be installed straight up, neither advanced or retarded from his design. However, you have determined that you are making too much horsepower down low and can't hook the tires up. You want to trade off a little of the lower end power for some higher end power. You might, in this case, install the camshaft slightly retarded. Although all four events (intake open, intake close, exhaust open, exhaust close) will be affected by changing the camshaft timing, the most important one will be the intake closing point. If you retard the camshaft, you will be closing the intake later, thus bleeding off some of the cylinder pressure and resulting in less low end power. Vice versa if you advance the camshaft. More bottom end, less top end.
+Intake Centerline:
+*This number represents where the intake lobe's peak lift occurs in relation to crankshaft rotation.  It is the point of maximum lift of the intake lobe and is measured in ''crankshaft'' degrees.  A cam ground "straight up" will mean that the exhaust lobe's peak lift will happen at the same amount of degrees before top dead center, as the intake valve will peak after top dead center.  ICL is machined into the cam.  When cam manufacturers machine the snout of the cam for the cam sprocket, they will drill the holes with the cam slightly advanced, retarded, or straight up.  When installed with stock components, the ICL can't be altered.  Aftermarket timing chains and sprockets often have provisions for altering how the sprocket attaches to the cam and therefore you can counteract the ICL ground into the cam.  If the LSA value is the same as ICL, the cam is ground "straight up."  If the ICL is less than the LSA, it is ground advanced by the difference.  If ICL is more than the LSA, the cam is ground retarded.  For instance, if the cam has a 110-degree LSA with a 106 ICL, the cam is advanced by 4 degrees.
+Exhaust Centerline:
+*This number represents where the exhaust lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the exhaust lobe and is measure in crankshaft degrees.
+'''Phasing the camshaft:'''
+While is is true that you cannot change the lobes of a camshaft after it is ground (unless you re-grind the lobes), you can alter the characteristics of the camshaft in your motor by installing it in either a retarded or advanced position relative to the crankshaft rotation. For instance, the manufacturer recommends the camshaft to be installed straight up, neither advanced or retarded from his design. However, you have determined that you are making too much horsepower down low and can't hook the tires up. You want to trade off a little of the lower end power for some higher end power. You might, in this case, install the camshaft slightly retarded. Although all four events (intake open, intake close, exhaust open, exhaust close) will be affected by changing the camshaft timing, the most important one will be the intake closing point. If you retard the camshaft, you will be closing the intake later, thus bleeding off some of the cylinder pressure and resulting in less low end power. Vice versa if you advance the camshaft. More bottom end, less top end.
 == How does all of that affect my engine's power? ==