Spec cards not always accurate
07-24-2009, 08:19 PM
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Spec cards not always accurate Anyone ever look at advertised cam specs and think this is exactly what they are getting?
The valve lift specification of a Camshaft,is the distance that the intake or exhaust valve on a given engine comes off its seat.What I am wondering is how a manufacturer such as Comp Cams,achieves accurate cam specs on an engine designed to work on...say a Chevrolet small block between 55-98 when there are too many variables between the rocker arm ratio's between those years.
Example: lobe lift:.310 x rocker ratio: 1.5= .465 valve lift
lobe lift:.310 x rocker ratio : 1.6= .496 valve lift
pretty substantial increase
http://www.compcams.com/Cam_Specs/Browse.aspx
The valve lift specification of a Camshaft,is the distance that the intake or exhaust valve on a given engine comes off its seat.What I am wondering is how a manufacturer such as Comp Cams,achieves accurate cam specs on an engine designed to work on...say a Chevrolet small block between 55-98 when there are too many variables between the rocker arm ratio's between those years.
Example: lobe lift:.310 x rocker ratio: 1.5= .465 valve lift
lobe lift:.310 x rocker ratio : 1.6= .496 valve lift
pretty substantial increase
http://www.compcams.com/Cam_Specs/Browse.aspx
Last edited by lovescamaros28; 07-24-2009 at 08:25 PM.
07-24-2009, 08:53 PM
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from my experiences the advertised lift is the increase or lift the camshaft has not how much it opens the valve. no manufacturer could possibly quote that cuz they obviously dont know the size of your lifters, pushrods, rockerarms, valves etc.
07-24-2009, 08:58 PM
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Valve lift is always quoted based on the stock rocker ratio for a given engine family. All SBC cams are based on 1.5 ratio rockers unless otherwise noted. One good example of an exception is Comps XFI series of cams for LT1/LT4 engines, these are rated at 1.6. Most other LT1 cams are rated at 1.5.
LS series cams are generally rated 1.7 with the LS7 being the exception which is 1.8.
Shane
LS series cams are generally rated 1.7 with the LS7 being the exception which is 1.8.
Shane
07-24-2009, 10:24 PM
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Valve lift is always quoted based on the stock rocker ratio for a given engine family. All SBC cams are based on 1.5 ratio rockers unless otherwise noted. One good example of an exception is Comps XFI series of cams for LT1/LT4 engines, these are rated at 1.6. Most other LT1 cams are rated at 1.5.
LS series cams are generally rated 1.7 with the LS7 being the exception which is 1.8.
Shane
LS series cams are generally rated 1.7 with the LS7 being the exception which is 1.8.
Shane
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07-28-2009, 08:03 PM
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Are you talking about when it says int/exh lift at or not at .050?
Since even your example says "lobe lift" ...when you degree a cam you put a solid lifter and dial indicator on top of the lifter and measure the "lobe lift" not the "valve lift" or am I thinking about something different? so if a cam has .500 lobe lift that is the same no matter what rocker ratio or variables you got.
Since even your example says "lobe lift" ...when you degree a cam you put a solid lifter and dial indicator on top of the lifter and measure the "lobe lift" not the "valve lift" or am I thinking about something different? so if a cam has .500 lobe lift that is the same no matter what rocker ratio or variables you got.
