How important is Lift on Camshafts? Experts
09-25-2003, 02:32 PM
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How important is Lift on Camshafts? Experts Let's take two cam specs....
224/224 .581"I .581" E 112LSA
224/224 .481"I .481" E 112LSA
Now dynoing both cams in the same exact car. How much more power would the .581" Lift make over the .481" Lift cam? A lot or alittle?
One last question.. What is the Max lift the stock springs can handle in an LS1?
224/224 .581"I .581" E 112LSA
224/224 .481"I .481" E 112LSA
Now dynoing both cams in the same exact car. How much more power would the .581" Lift make over the .481" Lift cam? A lot or alittle?
One last question.. What is the Max lift the stock springs can handle in an LS1?
09-25-2003, 02:39 PM
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Re: How important is Lift on Camshafts? Experts depends solely on the cyllinder heads. check out this article. very last paragraph.
http://www.speeddemonmotorsports.com...Cam_Timing.htm
http://www.speeddemonmotorsports.com...Cam_Timing.htm
09-26-2003, 07:18 AM
#3
Re: How important is Lift on Camshafts? Experts Instead of the two arbitrary lift numbers lets take two we actually come across here.
224/224 .581/.581
224/224 .568/.568
The difference in those cams is .013 of lift. Not a whole ton but enough that it makes a big difference in things.
There is probably 5-7hp in that added lift, but there is also more valvespring wear, the need for a stronger spring because the cam has a more aggressive path to get to the higher lift.
To clear that up for guys, think about duration as the amount of time the valve is open. The more lift you try to squeeze into that amount of time takes a more aggressive cam lobe. The part that is going to be more aggressive is the area were the cam moves from zero lift (base circle) to where it starts to open the valve. That's called the ramp. The ramp needs to start the lifter up the flank of the lobe faster, the higher it needs to go, the higher the angle of the flank. The ramp dictates all of this. The more aggressive ramp needs more force on it to keep the lifter on the cam. I hope that makes sense.
Now with the stronger spring you need stronger lifters to hold up to it and stronger parts like rocker arms and pushrods so they don't flex.
So the smaller lift 224 cam will be easier on the rest of the parts for a loss of 5hp, that's one thing that should go into a cam choice.
As for stock springs, they should never be used on any aftermarket cam. So don't go there.
Bret
224/224 .581/.581
224/224 .568/.568
The difference in those cams is .013 of lift. Not a whole ton but enough that it makes a big difference in things.
There is probably 5-7hp in that added lift, but there is also more valvespring wear, the need for a stronger spring because the cam has a more aggressive path to get to the higher lift.
To clear that up for guys, think about duration as the amount of time the valve is open. The more lift you try to squeeze into that amount of time takes a more aggressive cam lobe. The part that is going to be more aggressive is the area were the cam moves from zero lift (base circle) to where it starts to open the valve. That's called the ramp. The ramp needs to start the lifter up the flank of the lobe faster, the higher it needs to go, the higher the angle of the flank. The ramp dictates all of this. The more aggressive ramp needs more force on it to keep the lifter on the cam. I hope that makes sense.
Now with the stronger spring you need stronger lifters to hold up to it and stronger parts like rocker arms and pushrods so they don't flex.
So the smaller lift 224 cam will be easier on the rest of the parts for a loss of 5hp, that's one thing that should go into a cam choice.
As for stock springs, they should never be used on any aftermarket cam. So don't go there.
Bret
09-26-2003, 08:20 AM
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Re: How important is Lift on Camshafts? Experts
Instead of the two arbitrary lift numbers lets take two we actually come across here.
224/224 .581/.581
224/224 .568/.568
The difference in those cams is .013 of lift. Not a whole ton but enough that it makes a big difference in things.
There is probably 5-7hp in that added lift,
224/224 .581/.581
224/224 .568/.568
The difference in those cams is .013 of lift. Not a whole ton but enough that it makes a big difference in things.
There is probably 5-7hp in that added lift,
I had no idea that small amount of lift could make such a diff in power....so here's my scenario.
I want to go from my 228/224 .588 .581 114 to a 232/236 .571/.577 112...my goal was to make 5 to 8rwhp from the cam swap. since I am losing lift but gaining duration, would it kinda even itslef out?? no reaon to go thru the trouble for zero or very minimal gain.
TIA
Alex
09-26-2003, 09:06 AM
#5
Re: How important is Lift on Camshafts? Experts Alex,
The cam duration and LSA will have a greater effect on the power range, but I think that your choice of staying in the same lift range is a good one.
To me I'm not sure if there is going to be a big gain there. A 232/236 will be a good cam, and you could see more power from that. You could also go to a 232/242 .575/.566 112 and have a less agressive LG cam.
Bret
The cam duration and LSA will have a greater effect on the power range, but I think that your choice of staying in the same lift range is a good one.
To me I'm not sure if there is going to be a big gain there. A 232/236 will be a good cam, and you could see more power from that. You could also go to a 232/242 .575/.566 112 and have a less agressive LG cam.
Bret
09-26-2003, 09:25 AM
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Re: How important is Lift on Camshafts? Experts Lift does make a big difference...especially in the upper RPM's..combined with a head that flows well around .580-.600 lift. No sense in having a head that flows weel at .600 and a cam that doesn't open that far..
Then again I could be wrong....probably
Then again I could be wrong....probably
09-27-2003, 02:49 AM
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Re: How important is Lift on Camshafts? Experts Dont forget that the cam has it's own lift rating, which is then multiplied by the rocker arm (1.7 stock). Then you have your total valve lift. 
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09-27-2003, 06:45 AM
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Re: How important is Lift on Camshafts? Experts I like to think of more lift as good to raise torque, and duration adds horsepower. In similar cams changing only these specs. will have those effects. Kind of like a rule of thumb. For example running hi ratio rockers on my SBC on intakes only raised lift appreciably, barely changed .050" duration(+5*) When dyno tested it picked up 20 ft.lbs of torque in mid range, but power gained was less because this effect barely extended rpm range. Make sense? 
09-27-2003, 07:05 AM
#9
Re: How important is Lift on Camshafts? Experts HP is torque. If it raised your tourque 20 lbs then it raised the hp at that rpm. HP= (TQ*RPM)/5252 that is the formula. That is how you figure HP. See what I meen? so you raised the hp in the middrange as well. If you raised the tq 20 then I bet the hp went up even more at that same rpm.
09-28-2003, 01:26 AM
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Re: How important is Lift on Camshafts? Experts
HP is torque. If it raised your tourque 20 lbs then it raised the hp at that rpm. HP= (TQ*RPM)/5252 that is the formula. That is how you figure HP. See what I meen? so you raised the hp in the middrange as well. If you raised the tq 20 then I bet the hp went up even more at that same rpm.
Ok then how would you say this in HP in the shortest way possible : an engine gained 20 ft lbs from 3,000 to 5,550 RPM.:
Sure the gain was 11.4 Hp at 3,000 and 21 HP at 5550 but isn't it easier to say that they picked up "20lbs from this to that" or i.e. "20lbs in midrange" Saying someone gained HP in midrange means less to me than saying they picked up torque. Saying someone picked up 10 lbs of torque at 7000 RPM means little to me, but telling me that it added 13HP to their "PEAK HP" means alot to me. Maybe I am nuts but that is what makes me see things clearer. Too each his own I guess.
09-28-2003, 08:03 AM
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Re: How important is Lift on Camshafts? Experts
HP is torque. If it raised your tourque 20 lbs then it raised the hp at that rpm. HP= (TQ*RPM)/5252 that is the formula. That is how you figure HP. See what I meen? so you raised the hp in the middrange as well. If you raised the tq 20 then I bet the hp went up even more at that same rpm.
09-28-2003, 08:47 PM
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Re: How important is Lift on Camshafts? Experts
HP is torque. If it raised your tourque 20 lbs then it raised the hp at that rpm. HP= (TQ*RPM)/5252 that is the formula. That is how you figure HP. See what I meen? so you raised the hp in the middrange as well. If you raised the tq 20 then I bet the hp went up even more at that same rpm.
09-28-2003, 08:47 PM
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Re: How important is Lift on Camshafts? Experts
HP is torque. If it raised your tourque 20 lbs then it raised the hp at that rpm. HP= (TQ*RPM)/5252 that is the formula. That is how you figure HP. See what I meen? so you raised the hp in the middrange as well. If you raised the tq 20 then I bet the hp went up even more at that same rpm.
09-29-2003, 01:15 PM
#15
Re: How important is Lift on Camshafts? Experts **** it looks like I pushed this off track. Sorry for that. I was not trying to start a flame. If I miss spell something, overlook it. I am terrible at spelling but I am much better at Mechanical Theory.
Ok, So you are saying you have seen a 20lbs gain in torque but no gain in HP. I think you ment you did not see any gain in HP were you expected to see it. If you incress torque you will incress HP at the exact same RPM you incressed the Torque. It has to due to the way HP is calculated.
Ok, So you are saying you have seen a 20lbs gain in torque but no gain in HP. I think you ment you did not see any gain in HP were you expected to see it. If you incress torque you will incress HP at the exact same RPM you incressed the Torque. It has to due to the way HP is calculated.
09-30-2003, 07:59 PM
#16
Re: How important is Lift on Camshafts? Experts Also, that is not my formula, that is the industry standered. Hp is directly related to TQ. I understand what you are saying. It is easier to understand power by looking at the HP numbers. That is why the industry uses HP numbers to make it easier to understand. Now you may ask why they even tell you Peak torque too. Marketing. It sounds better to say this engine makes 350 hp at 5300 and 400 tq at 2800 then to say 350 hp at 5300 and 150 hp at 2800. Using both terms makes it easier to understand what rpm range a given engine makes energy. So what I am saying is torque is what makes the car move at any RPM range. HP is an easier way to understand that. HP is just a term used to express that.
As for the answer to the origanal question, The lift of your cam should be dictated by the max flow rate of your heads. If the heads stop flowing at .400 why lift the valves to .700? You are just waisting money. Also there is a point to were it becomes a bad think. Too much lift can hurt you. But you never know without flowing your heads first. If your heads are stock I can give you the flow numbers. They will be close but remember there is always a little deviation between heads.
As for the HP thing, I am finished with that.
And yes, I misspelled a lot more words. Spelling I was never good at.
As for the answer to the origanal question, The lift of your cam should be dictated by the max flow rate of your heads. If the heads stop flowing at .400 why lift the valves to .700? You are just waisting money. Also there is a point to were it becomes a bad think. Too much lift can hurt you. But you never know without flowing your heads first. If your heads are stock I can give you the flow numbers. They will be close but remember there is always a little deviation between heads.
As for the HP thing, I am finished with that.
And yes, I misspelled a lot more words. Spelling I was never good at.
10-01-2003, 02:56 AM
#17
Re: How important is Lift on Camshafts? Experts very well put...heres a link to help with the overall understanding of how it all works and why it all works....
Its easier to understand the whole lift duration thing after you see this...
you gotta remember our engine is just a big air pump....
http://auto.howstuffworks.com/engine.htm
also everything changes as the rpms go higher....you gotta pick and choose where you want your main powerband to be...and sacrifice a little in the other areas to get it...
oh...and you gotta have enough airflow coming in to make the lift worth while....having too much lift on the heads wont hurt you at all...its called stalling the heads....you will get a very flat torque curve from it....If you dont have enough coming in from the intake...you will have a very peaky torque curv....and make lower power #'s
stalling the heads is the right Idea...having flow tests done before ordering heads is the best way to find out which heads you will benefit the most from...just get the ones that are slightly(very slihgtly) under or at your flow #'s(or have them ported for you to your specs) and you will have a very flat torque curve and a high HP #.
Its easier to understand the whole lift duration thing after you see this...
you gotta remember our engine is just a big air pump....
http://auto.howstuffworks.com/engine.htm
also everything changes as the rpms go higher....you gotta pick and choose where you want your main powerband to be...and sacrifice a little in the other areas to get it...
oh...and you gotta have enough airflow coming in to make the lift worth while....having too much lift on the heads wont hurt you at all...its called stalling the heads....you will get a very flat torque curve from it....If you dont have enough coming in from the intake...you will have a very peaky torque curv....and make lower power #'s
stalling the heads is the right Idea...having flow tests done before ordering heads is the best way to find out which heads you will benefit the most from...just get the ones that are slightly(very slihgtly) under or at your flow #'s(or have them ported for you to your specs) and you will have a very flat torque curve and a high HP #.
10-01-2003, 07:30 AM
#18
6600 rpm clutch dump of death Administrator
Re: How important is Lift on Camshafts? Experts Don't know if I necessarily agree 100% with each of them, but here are two points of view on the matter. David Reher, and Dmitri Elgin
David Reher:
Textbooks would lead you to believe that an exhaust to intake flow ratio of 80 percent is ideal - yet a typical Pro Stock head has exhaust ports that flow less than 60 percent of the intake runners. You can improve the exhaust flow
tremendously with about 40 minutes of work with a hand grinder - but the supposed improvements will just about kill the engine's on-track performance. I know because I've been there.
We have also learned that low-lift flow (meaning anything below .400-inch valve lift in a Pro Stock engine with a .900-inch lift camshaft) is relatively unimportant. Think about the valve events in a racing engine: From the point when the valve first moves off its seat until it reaches mid-lift, the piston is either going the wrong way (that is, it is rising in the cylinder) or it's parked near TDC. The piston doesn't begin to move away from the combustion chamber with enough velocity to lower the pressure in the cylinder until the valve is nearly halfway open. Consequently it is high-lift flow that really matters in a drag racing engine.
ELGIN CAM DESIGN PHILOSOPHY
You probably have figured out by now that I am not an advocate of extra high lift, unnecessarily long duration, or very high compression for any street driven car. I prefer instead to use maximum velocity in the camshaft design which allows my cams to have more duration at 0.050", 0.100", and 0.200" lift compared to the "Brand X" cams you might get from other sources. As a side benefit of this design choice, it turns out that when you have more duration at 0.200" - 0.300" lift and not as high a cam lift, you end up with a cam lobe with a rounder nose radius which will support higher valve spring loads and therefore will last longer than a "pointed" high lift cam. I learned a long time ago that dwell on the nose, or top, portion of the cam lobe is equivalent to lift provided that you have the valve open far enough when the piston reaches its maximum velocity. On a normally aspirated engine, I have never seen power increased by adding valve lift above and beyond the flow capacity of the head.
You now have all the info you need to make the important performance enhancement choices appropriate for your own application - so there is not much more to say except HAPPY TUNING.
By: Dimitri N. Elgin
Now, my take on things. You can trade lift for duration or vice versa to a certain extent. I run a car with a buddy in a class that is limited in lift, so we simply added tons of duration to make that loss of lift back up. Alos, keep in mind the ammount of time your cam stays at one point. It stays a the mid lift ranges much longer than it ever does at the peak lift zones. That is perhaps 20% of the total "event". You can always round the nose of the cam and at lower lift keep the cam open longer than you would with a cam with a bit more lift.
Ther eisa really a lot to it, but all things being equal it going to depend on your heads,your valve events, etc...
But in general the cam with more lift will make a bit more power....
David Reher:
Textbooks would lead you to believe that an exhaust to intake flow ratio of 80 percent is ideal - yet a typical Pro Stock head has exhaust ports that flow less than 60 percent of the intake runners. You can improve the exhaust flow
tremendously with about 40 minutes of work with a hand grinder - but the supposed improvements will just about kill the engine's on-track performance. I know because I've been there.
We have also learned that low-lift flow (meaning anything below .400-inch valve lift in a Pro Stock engine with a .900-inch lift camshaft) is relatively unimportant. Think about the valve events in a racing engine: From the point when the valve first moves off its seat until it reaches mid-lift, the piston is either going the wrong way (that is, it is rising in the cylinder) or it's parked near TDC. The piston doesn't begin to move away from the combustion chamber with enough velocity to lower the pressure in the cylinder until the valve is nearly halfway open. Consequently it is high-lift flow that really matters in a drag racing engine.
ELGIN CAM DESIGN PHILOSOPHY
You probably have figured out by now that I am not an advocate of extra high lift, unnecessarily long duration, or very high compression for any street driven car. I prefer instead to use maximum velocity in the camshaft design which allows my cams to have more duration at 0.050", 0.100", and 0.200" lift compared to the "Brand X" cams you might get from other sources. As a side benefit of this design choice, it turns out that when you have more duration at 0.200" - 0.300" lift and not as high a cam lift, you end up with a cam lobe with a rounder nose radius which will support higher valve spring loads and therefore will last longer than a "pointed" high lift cam. I learned a long time ago that dwell on the nose, or top, portion of the cam lobe is equivalent to lift provided that you have the valve open far enough when the piston reaches its maximum velocity. On a normally aspirated engine, I have never seen power increased by adding valve lift above and beyond the flow capacity of the head.
You now have all the info you need to make the important performance enhancement choices appropriate for your own application - so there is not much more to say except HAPPY TUNING.
By: Dimitri N. Elgin
Now, my take on things. You can trade lift for duration or vice versa to a certain extent. I run a car with a buddy in a class that is limited in lift, so we simply added tons of duration to make that loss of lift back up. Alos, keep in mind the ammount of time your cam stays at one point. It stays a the mid lift ranges much longer than it ever does at the peak lift zones. That is perhaps 20% of the total "event". You can always round the nose of the cam and at lower lift keep the cam open longer than you would with a cam with a bit more lift.
Ther eisa really a lot to it, but all things being equal it going to depend on your heads,your valve events, etc...
But in general the cam with more lift will make a bit more power....
10-01-2003, 08:25 AM
#19
Re: How important is Lift on Camshafts? Experts
Don't know if I necessarily agree 100% with each of them, but here are two points of view on the matter. David Reher, and Dmitri Elgin
David Reher:
Textbooks would lead you to believe that an exhaust to intake flow ratio of 80 percent is ideal - yet a typical Pro Stock head has exhaust ports that flow less than 60 percent of the intake runners. You can improve the exhaust flow
tremendously with about 40 minutes of work with a hand grinder - but the supposed improvements will just about kill the engine's on-track performance. I know because I've been there.
We have also learned that low-lift flow (meaning anything below .400-inch valve lift in a Pro Stock engine with a .900-inch lift camshaft) is relatively unimportant. Think about the valve events in a racing engine: From the point when the valve first moves off its seat until it reaches mid-lift, the piston is either going the wrong way (that is, it is rising in the cylinder) or it's parked near TDC. The piston doesn't begin to move away from the combustion chamber with enough velocity to lower the pressure in the cylinder until the valve is nearly halfway open. Consequently it is high-lift flow that really matters in a drag racing engine.
ELGIN CAM DESIGN PHILOSOPHY
You probably have figured out by now that I am not an advocate of extra high lift, unnecessarily long duration, or very high compression for any street driven car. I prefer instead to use maximum velocity in the camshaft design which allows my cams to have more duration at 0.050", 0.100", and 0.200" lift compared to the "Brand X" cams you might get from other sources. As a side benefit of this design choice, it turns out that when you have more duration at 0.200" - 0.300" lift and not as high a cam lift, you end up with a cam lobe with a rounder nose radius which will support higher valve spring loads and therefore will last longer than a "pointed" high lift cam. I learned a long time ago that dwell on the nose, or top, portion of the cam lobe is equivalent to lift provided that you have the valve open far enough when the piston reaches its maximum velocity. On a normally aspirated engine, I have never seen power increased by adding valve lift above and beyond the flow capacity of the head.
You now have all the info you need to make the important performance enhancement choices appropriate for your own application - so there is not much more to say except HAPPY TUNING.
By: Dimitri N. Elgin
Now, my take on things. You can trade lift for duration or vice versa to a certain extent. I run a car with a buddy in a class that is limited in lift, so we simply added tons of duration to make that loss of lift back up. Alos, keep in mind the ammount of time your cam stays at one point. It stays a the mid lift ranges much longer than it ever does at the peak lift zones. That is perhaps 20% of the total "event". You can always round the nose of the cam and at lower lift keep the cam open longer than you would with a cam with a bit more lift.
Ther eisa really a lot to it, but all things being equal it going to depend on your heads,your valve events, etc...
But in general the cam with more lift will make a bit more power....
David Reher:
Textbooks would lead you to believe that an exhaust to intake flow ratio of 80 percent is ideal - yet a typical Pro Stock head has exhaust ports that flow less than 60 percent of the intake runners. You can improve the exhaust flow
tremendously with about 40 minutes of work with a hand grinder - but the supposed improvements will just about kill the engine's on-track performance. I know because I've been there.
We have also learned that low-lift flow (meaning anything below .400-inch valve lift in a Pro Stock engine with a .900-inch lift camshaft) is relatively unimportant. Think about the valve events in a racing engine: From the point when the valve first moves off its seat until it reaches mid-lift, the piston is either going the wrong way (that is, it is rising in the cylinder) or it's parked near TDC. The piston doesn't begin to move away from the combustion chamber with enough velocity to lower the pressure in the cylinder until the valve is nearly halfway open. Consequently it is high-lift flow that really matters in a drag racing engine.
ELGIN CAM DESIGN PHILOSOPHY
You probably have figured out by now that I am not an advocate of extra high lift, unnecessarily long duration, or very high compression for any street driven car. I prefer instead to use maximum velocity in the camshaft design which allows my cams to have more duration at 0.050", 0.100", and 0.200" lift compared to the "Brand X" cams you might get from other sources. As a side benefit of this design choice, it turns out that when you have more duration at 0.200" - 0.300" lift and not as high a cam lift, you end up with a cam lobe with a rounder nose radius which will support higher valve spring loads and therefore will last longer than a "pointed" high lift cam. I learned a long time ago that dwell on the nose, or top, portion of the cam lobe is equivalent to lift provided that you have the valve open far enough when the piston reaches its maximum velocity. On a normally aspirated engine, I have never seen power increased by adding valve lift above and beyond the flow capacity of the head.
You now have all the info you need to make the important performance enhancement choices appropriate for your own application - so there is not much more to say except HAPPY TUNING.
By: Dimitri N. Elgin
Now, my take on things. You can trade lift for duration or vice versa to a certain extent. I run a car with a buddy in a class that is limited in lift, so we simply added tons of duration to make that loss of lift back up. Alos, keep in mind the ammount of time your cam stays at one point. It stays a the mid lift ranges much longer than it ever does at the peak lift zones. That is perhaps 20% of the total "event". You can always round the nose of the cam and at lower lift keep the cam open longer than you would with a cam with a bit more lift.
Ther eisa really a lot to it, but all things being equal it going to depend on your heads,your valve events, etc...
But in general the cam with more lift will make a bit more power....
10-01-2003, 06:18 PM
#20
Re: How important is Lift on Camshafts? Experts so would it be feasible to say a low lift cam...with a lot of duration.....and a set of 1.85 rockers would make the same power as a car with a cam with the same specs other than the lift??? If that lift was the same end result???
cam 1- lift .525....add 1.85 rockes..lift = .571
cam 2- lift .571...1.7 rockers...
all other specs the same..would there be any difference???
if so??? then maybe a daily driver with springs ready for the .571 lift...but keep 1.7 rockes on...and only put 1.85 at the track...
only about 30minutes of work to change them over at the track...
any thoughts???
cam 1- lift .525....add 1.85 rockes..lift = .571
cam 2- lift .571...1.7 rockers...
all other specs the same..would there be any difference???
if so??? then maybe a daily driver with springs ready for the .571 lift...but keep 1.7 rockes on...and only put 1.85 at the track...
only about 30minutes of work to change them over at the track...
any thoughts???