camshft driveability
04-15-2008, 02:51 PM
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camshft driveability I understand that much of what makes a camshaft a good street driver has to do with the exhaust valve events. Can someone explain this and are there other factors like max overlap, advanced / retard cam timing, etc. that help with driveability when choosing a cam?
04-15-2008, 03:22 PM
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Cam Basics:
When deciding which camshaft is right for you, the best you can do is try to make an educated guess based on previous experiences or other's experiences. There are countless books about camshaft design and theory, so trying to explain what all to choose is pointless and this is why vendors are out there to see what works well in the LS1 for us. They do the research, and thus, they get our money.
When buying a cam, you'll see specs like "220/224 0.550/0.558 114lsa". The first two numbers are intake duration (in degrees) followed by exhaust duration (in degrees). The next two numbers are valve lift for the intake (in inches) and valve lift for the exhaust (in inches).Finally, the last number is the Lobe Separation Angle.
Duration:
Duration really plays a big factor in how the cam will drive and idle. The bigger the duration, the longer the valves stay open, and generally the 'lopier' and worse driving the cam will be. The numbers you'll usually see are the duration in degrees that the valve is open MORE than 0.050" of an inch. Cam cards will also list duration at 0 lift, and that will be a number like 270-290'ish. Cams that have the same duration for intake and exhaust are symmetrical, cams with more intake than exhaust are called "reverse split", and cams with more exhaust than intake are sometimes referred to as "traditional split".
LSA (Lobe Separation Angle):
Lobe Separation Angle, usually referred to as "LSA", is the angle of separation between the exhaust peak and intake peak. The lower the angle, the more the lobes will overlap, and that means more lope, gas smell, and drivability issues...however, the lower LSA can also mean more power and you get it sooner in the RPM range to boot. Duration and LSA are 2 very important items in clueing you into how a cam will idle and drive, although there is a LOT more to a cam than this.
Lift:
Cam lift, in my opinion, is less of a complicated matter on these motors. There's not much of a reason to run less than 0.550" of valve lift, so anything between 0.550 and 0.600" is probably going to be fine. If you have ported heads, it may be best to lean towards cams with 0.570" lift and up as most ported heads will just keep flowing more and more as that valve lift increases. Note that a cam card will show lobe lift, which is the actual lift of the cam lobe. Once you take lobe lift and multiply it by the ratio of the rocker arm (stock is 1.7), you get valve lift.
Lobe Profile
The Lobe profile of a cam basically is the curve at which a valve is opened and closed. Some lobes are very EXTREME and will snap a valve open very quickly and then slam it shut, while others are "softer" and slowly open and close valves. The more extreme the lobe, the noisier your valvetrain will be and the harder it is on your valve springs...however, a more extreme lobe will generally idle better than a less extreme lobe with the same duration at 50 thousandths. If your cam has very aggressive lobes and your cam lift is up there, I'd suggest you try to lighten your valvetrain by getting titanium retainers if possible.
Choosing the cam for you
For cars that need to stay stock sounding and driving, but still want a kick in the pants for horsepower, something between a 214 and 220'ish duration would probably be best. For the majority of the cars out there, anything in the 221-227 range is probably a better selection, and for the guys that want all they can get 228+ duration cam shafts are generally the minimum. As a novice all you can do is ask around, listen to cars, look at track/dyno results, and make your best guess. As long as you pick a cam close to what might fit you (i.e. mild, average, or extreme given the criteria above) you really can't go wrong. It's not a life or death decision here. A few degrees here and there isn't something you should sweat about until you've gotten a few cams under your belt and know more about what you want.
Choosing the valvetrain upgrades:
Now, you can't just throw a cam in and call it a day. At the BARE minimum your valvesprings *must* be replaced with stiffer ones. Whoever sells you the cam can also recommend a spring to go along with it...this is what vendors/shops are for, so you don't need to worry about being an expert on this (although it's not very complicated if you want to learn). Some springs will require aftermarket retainers (it's kind of a hat that sits on top of the spring), some won't, but in general if you go with a very aggressive cam and plan on spinning the engine up past 6600rpms I'd recommend getting Titanium retainers to help reduce the moving mass and keep the valvetrain moving crisply.
Next there are spring seats and valve seals....some spring setups may require you change the spring seat and install new valve seals as well. If your vendor requires you install this, I will cover their install in this document as well. Hardened pushrods will also be highly recommended, although quite a few have just stuck with the stock pushrods and not had issues.
When deciding which camshaft is right for you, the best you can do is try to make an educated guess based on previous experiences or other's experiences. There are countless books about camshaft design and theory, so trying to explain what all to choose is pointless and this is why vendors are out there to see what works well in the LS1 for us. They do the research, and thus, they get our money.
When buying a cam, you'll see specs like "220/224 0.550/0.558 114lsa". The first two numbers are intake duration (in degrees) followed by exhaust duration (in degrees). The next two numbers are valve lift for the intake (in inches) and valve lift for the exhaust (in inches).Finally, the last number is the Lobe Separation Angle.
Duration:
Duration really plays a big factor in how the cam will drive and idle. The bigger the duration, the longer the valves stay open, and generally the 'lopier' and worse driving the cam will be. The numbers you'll usually see are the duration in degrees that the valve is open MORE than 0.050" of an inch. Cam cards will also list duration at 0 lift, and that will be a number like 270-290'ish. Cams that have the same duration for intake and exhaust are symmetrical, cams with more intake than exhaust are called "reverse split", and cams with more exhaust than intake are sometimes referred to as "traditional split".
LSA (Lobe Separation Angle):
Lobe Separation Angle, usually referred to as "LSA", is the angle of separation between the exhaust peak and intake peak. The lower the angle, the more the lobes will overlap, and that means more lope, gas smell, and drivability issues...however, the lower LSA can also mean more power and you get it sooner in the RPM range to boot. Duration and LSA are 2 very important items in clueing you into how a cam will idle and drive, although there is a LOT more to a cam than this.
Lift:
Cam lift, in my opinion, is less of a complicated matter on these motors. There's not much of a reason to run less than 0.550" of valve lift, so anything between 0.550 and 0.600" is probably going to be fine. If you have ported heads, it may be best to lean towards cams with 0.570" lift and up as most ported heads will just keep flowing more and more as that valve lift increases. Note that a cam card will show lobe lift, which is the actual lift of the cam lobe. Once you take lobe lift and multiply it by the ratio of the rocker arm (stock is 1.7), you get valve lift.
Lobe Profile
The Lobe profile of a cam basically is the curve at which a valve is opened and closed. Some lobes are very EXTREME and will snap a valve open very quickly and then slam it shut, while others are "softer" and slowly open and close valves. The more extreme the lobe, the noisier your valvetrain will be and the harder it is on your valve springs...however, a more extreme lobe will generally idle better than a less extreme lobe with the same duration at 50 thousandths. If your cam has very aggressive lobes and your cam lift is up there, I'd suggest you try to lighten your valvetrain by getting titanium retainers if possible.
Choosing the cam for you
For cars that need to stay stock sounding and driving, but still want a kick in the pants for horsepower, something between a 214 and 220'ish duration would probably be best. For the majority of the cars out there, anything in the 221-227 range is probably a better selection, and for the guys that want all they can get 228+ duration cam shafts are generally the minimum. As a novice all you can do is ask around, listen to cars, look at track/dyno results, and make your best guess. As long as you pick a cam close to what might fit you (i.e. mild, average, or extreme given the criteria above) you really can't go wrong. It's not a life or death decision here. A few degrees here and there isn't something you should sweat about until you've gotten a few cams under your belt and know more about what you want.
Choosing the valvetrain upgrades:
Now, you can't just throw a cam in and call it a day. At the BARE minimum your valvesprings *must* be replaced with stiffer ones. Whoever sells you the cam can also recommend a spring to go along with it...this is what vendors/shops are for, so you don't need to worry about being an expert on this (although it's not very complicated if you want to learn). Some springs will require aftermarket retainers (it's kind of a hat that sits on top of the spring), some won't, but in general if you go with a very aggressive cam and plan on spinning the engine up past 6600rpms I'd recommend getting Titanium retainers to help reduce the moving mass and keep the valvetrain moving crisply.
Next there are spring seats and valve seals....some spring setups may require you change the spring seat and install new valve seals as well. If your vendor requires you install this, I will cover their install in this document as well. Hardened pushrods will also be highly recommended, although quite a few have just stuck with the stock pushrods and not had issues.
04-15-2008, 08:55 PM
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Cam Basics:
When deciding which camshaft is right for you, the best you can do is try to make an educated guess based on previous experiences or other's experiences. There are countless books about camshaft design and theory, so trying to explain what all to choose is pointless and this is why vendors are out there to see what works well in the LS1 for us. They do the research, and thus, they get our money.
When buying a cam, you'll see specs like "220/224 0.550/0.558 114lsa". The first two numbers are intake duration (in degrees) followed by exhaust duration (in degrees). The next two numbers are valve lift for the intake (in inches) and valve lift for the exhaust (in inches).Finally, the last number is the Lobe Separation Angle.
Duration:
Duration really plays a big factor in how the cam will drive and idle. The bigger the duration, the longer the valves stay open, and generally the 'lopier' and worse driving the cam will be. The numbers you'll usually see are the duration in degrees that the valve is open MORE than 0.050" of an inch. Cam cards will also list duration at 0 lift, and that will be a number like 270-290'ish. Cams that have the same duration for intake and exhaust are symmetrical, cams with more intake than exhaust are called "reverse split", and cams with more exhaust than intake are sometimes referred to as "traditional split".
LSA (Lobe Separation Angle):
Lobe Separation Angle, usually referred to as "LSA", is the angle of separation between the exhaust peak and intake peak. The lower the angle, the more the lobes will overlap, and that means more lope, gas smell, and drivability issues...however, the lower LSA can also mean more power and you get it sooner in the RPM range to boot. Duration and LSA are 2 very important items in clueing you into how a cam will idle and drive, although there is a LOT more to a cam than this.
Lift:
Cam lift, in my opinion, is less of a complicated matter on these motors. There's not much of a reason to run less than 0.550" of valve lift, so anything between 0.550 and 0.600" is probably going to be fine. If you have ported heads, it may be best to lean towards cams with 0.570" lift and up as most ported heads will just keep flowing more and more as that valve lift increases. Note that a cam card will show lobe lift, which is the actual lift of the cam lobe. Once you take lobe lift and multiply it by the ratio of the rocker arm (stock is 1.7), you get valve lift.
Lobe Profile
The Lobe profile of a cam basically is the curve at which a valve is opened and closed. Some lobes are very EXTREME and will snap a valve open very quickly and then slam it shut, while others are "softer" and slowly open and close valves. The more extreme the lobe, the noisier your valvetrain will be and the harder it is on your valve springs...however, a more extreme lobe will generally idle better than a less extreme lobe with the same duration at 50 thousandths. If your cam has very aggressive lobes and your cam lift is up there, I'd suggest you try to lighten your valvetrain by getting titanium retainers if possible.
Choosing the cam for you
For cars that need to stay stock sounding and driving, but still want a kick in the pants for horsepower, something between a 214 and 220'ish duration would probably be best. For the majority of the cars out there, anything in the 221-227 range is probably a better selection, and for the guys that want all they can get 228+ duration cam shafts are generally the minimum. As a novice all you can do is ask around, listen to cars, look at track/dyno results, and make your best guess. As long as you pick a cam close to what might fit you (i.e. mild, average, or extreme given the criteria above) you really can't go wrong. It's not a life or death decision here. A few degrees here and there isn't something you should sweat about until you've gotten a few cams under your belt and know more about what you want.
Choosing the valvetrain upgrades:
Now, you can't just throw a cam in and call it a day. At the BARE minimum your valvesprings *must* be replaced with stiffer ones. Whoever sells you the cam can also recommend a spring to go along with it...this is what vendors/shops are for, so you don't need to worry about being an expert on this (although it's not very complicated if you want to learn). Some springs will require aftermarket retainers (it's kind of a hat that sits on top of the spring), some won't, but in general if you go with a very aggressive cam and plan on spinning the engine up past 6600rpms I'd recommend getting Titanium retainers to help reduce the moving mass and keep the valvetrain moving crisply.
Next there are spring seats and valve seals....some spring setups may require you change the spring seat and install new valve seals as well. If your vendor requires you install this, I will cover their install in this document as well. Hardened pushrods will also be highly recommended, although quite a few have just stuck with the stock pushrods and not had issues.
When deciding which camshaft is right for you, the best you can do is try to make an educated guess based on previous experiences or other's experiences. There are countless books about camshaft design and theory, so trying to explain what all to choose is pointless and this is why vendors are out there to see what works well in the LS1 for us. They do the research, and thus, they get our money.
When buying a cam, you'll see specs like "220/224 0.550/0.558 114lsa". The first two numbers are intake duration (in degrees) followed by exhaust duration (in degrees). The next two numbers are valve lift for the intake (in inches) and valve lift for the exhaust (in inches).Finally, the last number is the Lobe Separation Angle.
Duration:
Duration really plays a big factor in how the cam will drive and idle. The bigger the duration, the longer the valves stay open, and generally the 'lopier' and worse driving the cam will be. The numbers you'll usually see are the duration in degrees that the valve is open MORE than 0.050" of an inch. Cam cards will also list duration at 0 lift, and that will be a number like 270-290'ish. Cams that have the same duration for intake and exhaust are symmetrical, cams with more intake than exhaust are called "reverse split", and cams with more exhaust than intake are sometimes referred to as "traditional split".
LSA (Lobe Separation Angle):
Lobe Separation Angle, usually referred to as "LSA", is the angle of separation between the exhaust peak and intake peak. The lower the angle, the more the lobes will overlap, and that means more lope, gas smell, and drivability issues...however, the lower LSA can also mean more power and you get it sooner in the RPM range to boot. Duration and LSA are 2 very important items in clueing you into how a cam will idle and drive, although there is a LOT more to a cam than this.
Lift:
Cam lift, in my opinion, is less of a complicated matter on these motors. There's not much of a reason to run less than 0.550" of valve lift, so anything between 0.550 and 0.600" is probably going to be fine. If you have ported heads, it may be best to lean towards cams with 0.570" lift and up as most ported heads will just keep flowing more and more as that valve lift increases. Note that a cam card will show lobe lift, which is the actual lift of the cam lobe. Once you take lobe lift and multiply it by the ratio of the rocker arm (stock is 1.7), you get valve lift.
Lobe Profile
The Lobe profile of a cam basically is the curve at which a valve is opened and closed. Some lobes are very EXTREME and will snap a valve open very quickly and then slam it shut, while others are "softer" and slowly open and close valves. The more extreme the lobe, the noisier your valvetrain will be and the harder it is on your valve springs...however, a more extreme lobe will generally idle better than a less extreme lobe with the same duration at 50 thousandths. If your cam has very aggressive lobes and your cam lift is up there, I'd suggest you try to lighten your valvetrain by getting titanium retainers if possible.
Choosing the cam for you
For cars that need to stay stock sounding and driving, but still want a kick in the pants for horsepower, something between a 214 and 220'ish duration would probably be best. For the majority of the cars out there, anything in the 221-227 range is probably a better selection, and for the guys that want all they can get 228+ duration cam shafts are generally the minimum. As a novice all you can do is ask around, listen to cars, look at track/dyno results, and make your best guess. As long as you pick a cam close to what might fit you (i.e. mild, average, or extreme given the criteria above) you really can't go wrong. It's not a life or death decision here. A few degrees here and there isn't something you should sweat about until you've gotten a few cams under your belt and know more about what you want.
Choosing the valvetrain upgrades:
Now, you can't just throw a cam in and call it a day. At the BARE minimum your valvesprings *must* be replaced with stiffer ones. Whoever sells you the cam can also recommend a spring to go along with it...this is what vendors/shops are for, so you don't need to worry about being an expert on this (although it's not very complicated if you want to learn). Some springs will require aftermarket retainers (it's kind of a hat that sits on top of the spring), some won't, but in general if you go with a very aggressive cam and plan on spinning the engine up past 6600rpms I'd recommend getting Titanium retainers to help reduce the moving mass and keep the valvetrain moving crisply.
Next there are spring seats and valve seals....some spring setups may require you change the spring seat and install new valve seals as well. If your vendor requires you install this, I will cover their install in this document as well. Hardened pushrods will also be highly recommended, although quite a few have just stuck with the stock pushrods and not had issues.
Great Info, All you need to make a decision
