how do they chose lift numbers on a cam?
04-27-2008, 07:46 AM
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how do they chose lift numbers on a cam? cuz im thinking about picking a cam in the .57X area but i havent really seen any so i was wondering how they determine the specific lift. someone care to explain it to me.
04-27-2008, 09:03 AM
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most modern roller grinds are very similar in terms of lift vs duration. There is a practical limit on how fast you can get lift due to the mechanical limitations of the materials used for the lifters. Inertia and other factors come into play as well. For the most part every manufacture will have very similar mainstream lift numbers for the same duration. If you are looking for a specific lift number (not sure why you would focus on that above duration and LSA unless you have some geometry limits, but to each his own), look at any cam with the lift you are looking for and then take the duration numbers as a starting point for all of the other vendors.
04-27-2008, 12:55 PM
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Some folks just do an RE (rectal extraction) while others look at things like head flow, intake, exhaust, desired performance and a bunch of other stuff before choosing both lift and duration. These folks are often a llittle more successful making power than the RE method. Some more than others, in fact.
04-27-2008, 01:46 PM
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It depends on who is doing the determining.
Some folks just do an RE (rectal extraction) while others look at things like head flow, intake, exhaust, desired performance and a bunch of other stuff before choosing both lift and duration. These folks are often a llittle more successful making power than the RE method. Some more than others, in fact.
Some folks just do an RE (rectal extraction) while others look at things like head flow, intake, exhaust, desired performance and a bunch of other stuff before choosing both lift and duration. These folks are often a llittle more successful making power than the RE method. Some more than others, in fact.
Is that a technical term
Sorry, just got a good laugh on that one.
04-27-2008, 02:52 PM
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04-27-2008, 08:25 PM
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Move over XER grind.. here comes the RE grind profile
as for reasoning and selection..
First, you have a durability specification, if you cannot pass this then go back to the drawing board. These are the mechanical limitations: Forces, accelerations, wear rates, hardness, valvetrain mass/inertia
Next you determine what flow you need to achieve your targets, keep in mind targets dont include just horsepower and torque, it also includes specific fuel consumption, emissions, and in cylinder flow (also includes port, piston, and combustion chamber design). Max power and low fuel consumption are usually oposite for cam selection... High lift and overlap are bad for low rpm cruising.. This is where small cams and boost come in.. Not too many people want to drive a LS7 running a 620hp cam grind as a daily driver.. And its not likely to pass fuel consumption and emissions targets..
Finally, once you have all your known values, you compare optimal for all situations and you compromise to achieve the best cam selection for that vehicle.
as for reasoning and selection..
First, you have a durability specification, if you cannot pass this then go back to the drawing board. These are the mechanical limitations: Forces, accelerations, wear rates, hardness, valvetrain mass/inertia
Next you determine what flow you need to achieve your targets, keep in mind targets dont include just horsepower and torque, it also includes specific fuel consumption, emissions, and in cylinder flow (also includes port, piston, and combustion chamber design). Max power and low fuel consumption are usually oposite for cam selection... High lift and overlap are bad for low rpm cruising.. This is where small cams and boost come in.. Not too many people want to drive a LS7 running a 620hp cam grind as a daily driver.. And its not likely to pass fuel consumption and emissions targets..
Finally, once you have all your known values, you compare optimal for all situations and you compromise to achieve the best cam selection for that vehicle.
05-01-2008, 04:58 PM
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most modern roller grinds are very similar in terms of lift vs duration. There is a practical limit on how fast you can get lift due to the mechanical limitations of the materials used for the lifters. Inertia and other factors come into play as well. For the most part every manufacture will have very similar mainstream lift numbers for the same duration. If you are looking for a specific lift number (not sure why you would focus on that above duration and LSA unless you have some geometry limits, but to each his own), look at any cam with the lift you are looking for and then take the duration numbers as a starting point for all of the other vendors.
the is not a practical limit to lift vs. duration there is alot of variables, a couple things being what kind of ramp is the lobe on, what size roller wheel on the lifter, etc.etc. the main thing is area under the curve that is what is important and yes i do agree that lift is the last thing u want to worry about, get the cam u want and just run as much lift as u can with that valvetrain setup and heads, also a good pointer - if ur valvetrain geometry / quality isnt that great and u know what kind of lift ur wanting to run try to get it as much out of the rocker as u can and not the lobe
also the manufactuers lobe profiles can be completely different and still have the same lift/duration as another cam
Last edited by r351winner; 05-01-2008 at 05:09 PM.
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05-01-2008, 05:07 PM
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Move over XER grind.. here comes the RE grind profile
as for reasoning and selection..
First, you have a durability specification, if you cannot pass this then go back to the drawing board. These are the mechanical limitations: Forces, accelerations, wear rates, hardness, valvetrain mass/inertia
Next you determine what flow you need to achieve your targets, keep in mind targets dont include just horsepower and torque, it also includes specific fuel consumption, emissions, and in cylinder flow (also includes port, piston, and combustion chamber design). Max power and low fuel consumption are usually oposite for cam selection... High lift and overlap are bad for low rpm cruising.. This is where small cams and boost come in.. Not too many people want to drive a LS7 running a 620hp cam grind as a daily driver.. And its not likely to pass fuel consumption and emissions targets..
Finally, once you have all your known values, you compare optimal for all situations and you compromise to achieve the best cam selection for that vehicle.
as for reasoning and selection..
First, you have a durability specification, if you cannot pass this then go back to the drawing board. These are the mechanical limitations: Forces, accelerations, wear rates, hardness, valvetrain mass/inertia
Next you determine what flow you need to achieve your targets, keep in mind targets dont include just horsepower and torque, it also includes specific fuel consumption, emissions, and in cylinder flow (also includes port, piston, and combustion chamber design). Max power and low fuel consumption are usually oposite for cam selection... High lift and overlap are bad for low rpm cruising.. This is where small cams and boost come in.. Not too many people want to drive a LS7 running a 620hp cam grind as a daily driver.. And its not likely to pass fuel consumption and emissions targets..
Finally, once you have all your known values, you compare optimal for all situations and you compromise to achieve the best cam selection for that vehicle.
also eventhough lsa is a hard thing to deal with a tighter lsa will normally help u with bottom end its normally the more duration u have that will move power up in the rpm range- its just normally when people have a large cam generally asociated an lsa on the smaller side they think that its their overlap that is killing their bottom end when its actually the degrees btdc that the intake valve is opening on the exhaust stroke while the piston is traveling up / pushing against column airflow- the more overlap would help keep that airflow up at bottom rpm
05-01-2008, 05:11 PM
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this motor sounds like a little street motor that will fun to pound on it is not going to be that crtical just get close on the cam specs and you will have just as much fun just know what ur heads flow and @ what lift / what rpm you are going to be turning / and how many inches ur filling up and that would be just fine on the street just put a good cam in it and go have fun with it
05-01-2008, 05:13 PM
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It depends on who is doing the determining.
Some folks just do an RE (rectal extraction) while others look at things like head flow, intake, exhaust, desired performance and a bunch of other stuff before choosing both lift and duration. These folks are often a llittle more successful making power than the RE method. Some more than others, in fact.
Some folks just do an RE (rectal extraction) while others look at things like head flow, intake, exhaust, desired performance and a bunch of other stuff before choosing both lift and duration. These folks are often a llittle more successful making power than the RE method. Some more than others, in fact.
05-01-2008, 08:14 PM
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05-03-2008, 07:33 PM
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thats funny because you really dont know who i am or what i do for all you would know i might be that cam designer, u just see 20 posts and think o this guy doesnt know ne thing - so what all do u not agree with and not saying i am right but i would like to know how i am mistaken to learn - and i am not being sarcastic
05-03-2008, 08:16 PM
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thats funny because you really dont know who i am or what i do for all you would know i might be that cam designer, u just see 20 posts and think o this guy doesnt know ne thing - so what all do u not agree with and not saying i am right but i would like to know how i am mistaken to learn - and i am not being sarcastic
