"Low" lift cam vs high lift........power difference?
#1
On The Tree
Thread Starter
"Low" lift cam vs high lift........power difference?
Let's say a 224/228 cam in an ls2. How much of a power difference would there be dropping to 550 lift instead of 600 or 612? I'm wondering how much of a sacrifice there would be to gain valvespring life/running cheaper factory springs. I dont know the advertised duration, so I don't know how aggressive the ramps are but either BTR or TSP most likely.
#2
TECH Senior Member
There would be a torque loss over the whole rev range. How much is anyone's guess.
#4
TECH Senior Member
iTrader: (4)
Long post - sorry
Without a cam doctor the profile of the cam lobes in question and overlaying them its a guess in my opinion.
For example we had the cam doctor lobe profile for a very aggressive Morgan 224/224 .578/.578 lift cam. We had the cam lobe profile for my Comp Cams XER 224/224 .581/.581 lift cam.
Just looking at lift numbers the difference appears to be .003 which wouldn't be much difference.
Overlaying the two lobe profiles show the XER cam had more than 1 percent cam lobe area. It was clear the XER was way more aggressive and more powerful than just .003 more lift would indicate.
looking at how aggressive the lobe are would probably tell one far mote than the lift numbers.
Rough rule of thumb:
One can get an ideal of the cam lobes by looking at the advertised duration at .006 and subtracting the advertised duration at .050
The lower the number the more aggressive the lobe the higher the number the less aggressive.
Difference in lift between two cams below is .013 but only a small part of the story.
224 XER cam lobe with .581 lift advertised duration at .006 lift as 273 degrees. The advertised duration at .050 lift is 224.
273 - 224 = 49
49 is very aggressive
The old XE 224 cam with .568 lift was advertised at .006 lift s 277 degrees. The advertised duration at .050 lift is 224.
277 - 224 = 53
53 is aggressive
Just looking at .581 lift vs .568 lift doesn't begin to tell the difference in these two cams.
Regarding spring life todays great quality springs can go ~75,000 miles or so when properly match with some of the roughly .625 lift cams.
Ok guess time .550 lift vs .610 or so lift depending on the cylinder heads and intake manifold probably between 10 to 25 whp
Without a cam doctor the profile of the cam lobes in question and overlaying them its a guess in my opinion.
For example we had the cam doctor lobe profile for a very aggressive Morgan 224/224 .578/.578 lift cam. We had the cam lobe profile for my Comp Cams XER 224/224 .581/.581 lift cam.
Just looking at lift numbers the difference appears to be .003 which wouldn't be much difference.
Overlaying the two lobe profiles show the XER cam had more than 1 percent cam lobe area. It was clear the XER was way more aggressive and more powerful than just .003 more lift would indicate.
looking at how aggressive the lobe are would probably tell one far mote than the lift numbers.
Rough rule of thumb:
One can get an ideal of the cam lobes by looking at the advertised duration at .006 and subtracting the advertised duration at .050
The lower the number the more aggressive the lobe the higher the number the less aggressive.
Difference in lift between two cams below is .013 but only a small part of the story.
224 XER cam lobe with .581 lift advertised duration at .006 lift as 273 degrees. The advertised duration at .050 lift is 224.
273 - 224 = 49
49 is very aggressive
The old XE 224 cam with .568 lift was advertised at .006 lift s 277 degrees. The advertised duration at .050 lift is 224.
277 - 224 = 53
53 is aggressive
Just looking at .581 lift vs .568 lift doesn't begin to tell the difference in these two cams.
Regarding spring life todays great quality springs can go ~75,000 miles or so when properly match with some of the roughly .625 lift cams.
Ok guess time .550 lift vs .610 or so lift depending on the cylinder heads and intake manifold probably between 10 to 25 whp
Last edited by 99 Black Bird T/A; 05-22-2020 at 06:23 PM.
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djr48312 (11-11-2023)
#7
Cam lift
I got a cam Ground at isky for my 408 stroker stock ls3 heads 11.1 compression he gave 224 236 578 in 598 exh 112 lsa when I asked about more lift he said it wouldn’t make that much of a difference with the stick heads because they flow at about there max cfm in that area any more lift would net negligible results
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#9
On The Tree
Thread Starter
I got a cam Ground at isky for my 408 stroker stock ls3 heads 11.1 compression he gave 224 236 578 in 598 exh 112 lsa when I asked about more lift he said it wouldn’t make that much of a difference with the stick heads because they flow at about there max cfm in that area any more lift would net negligible results
I just want 570 lift and want it to go 75k without pulling the heads off.....
#10
yeah I want this one too last for a while it won’t be a daily driver but I do want to be able to hit the road sometimes
#11
On The Tree
Thread Starter
Long post - sorry
Without a cam doctor the profile of the cam lobes in question and overlaying them its a guess in my opinion.
For example we had the cam doctor lobe profile for a very aggressive Morgan 224/224 .578/.578 lift cam. We had the cam lobe profile for my Comp Cams XER 224/224 .581/.581 lift cam.
Just looking at lift numbers the difference appears to be .003 which wouldn't be much difference.
Overlaying the two lobe profiles show the XER cam had more than 1 percent cam lobe area. It was clear the XER was way more aggressive and more powerful than just .003 more lift would indicate.
looking at how aggressive the lobe are would probably tell one far mote than the lift numbers.
Rough rule of thumb:
One can get an ideal of the cam lobes by looking at the advertised duration at .006 and subtracting the advertised duration at .050
The lower the number the more aggressive the lobe the higher the number the less aggressive.
Difference in lift between two cams below is .013 but only a small part of the story.
224 XER cam lobe with .581 lift advertised duration at .006 lift as 273 degrees. The advertised duration at .050 lift is 224.
273 - 224 = 49
49 is very aggressive
The old XE 224 cam with .568 lift was advertised at .006 lift s 277 degrees. The advertised duration at .050 lift is 224.
277 - 224 = 53
53 is aggressive
Just looking at .581 lift vs .568 lift doesn't begin to tell the difference in these two cams.
Regarding spring life todays great quality springs can go ~75,000 miles or so when properly match with some of the roughly .625 lift cams.
Ok guess time .550 lift vs .610 or so lift depending on the cylinder heads and intake manifold probably between 10 to 25 whp
Without a cam doctor the profile of the cam lobes in question and overlaying them its a guess in my opinion.
For example we had the cam doctor lobe profile for a very aggressive Morgan 224/224 .578/.578 lift cam. We had the cam lobe profile for my Comp Cams XER 224/224 .581/.581 lift cam.
Just looking at lift numbers the difference appears to be .003 which wouldn't be much difference.
Overlaying the two lobe profiles show the XER cam had more than 1 percent cam lobe area. It was clear the XER was way more aggressive and more powerful than just .003 more lift would indicate.
looking at how aggressive the lobe are would probably tell one far mote than the lift numbers.
Rough rule of thumb:
One can get an ideal of the cam lobes by looking at the advertised duration at .006 and subtracting the advertised duration at .050
The lower the number the more aggressive the lobe the higher the number the less aggressive.
Difference in lift between two cams below is .013 but only a small part of the story.
224 XER cam lobe with .581 lift advertised duration at .006 lift as 273 degrees. The advertised duration at .050 lift is 224.
273 - 224 = 49
49 is very aggressive
The old XE 224 cam with .568 lift was advertised at .006 lift s 277 degrees. The advertised duration at .050 lift is 224.
277 - 224 = 53
53 is aggressive
Just looking at .581 lift vs .568 lift doesn't begin to tell the difference in these two cams.
Regarding spring life todays great quality springs can go ~75,000 miles or so when properly match with some of the roughly .625 lift cams.
Ok guess time .550 lift vs .610 or so lift depending on the cylinder heads and intake manifold probably between 10 to 25 whp
The ls6 cam is 270/277 204/218. That's 66 and 59. I believe the ls6 was good for 100k? So 55 should be pretty good, sticking with 550 lift. I know there is more to it than that, but I'm betting the factory had pretty smooth lobes. So if I increase the adv duration a bit I should be able to go up to 570 lift and be a good compromise.
Trying to get a soft lobe, make good use of the 243 heads AND keep overlap low.....sigh.
#12
TECH Apprentice
If you have stock heads as long as your cam is at least .500 lift and over you'll get the benefit of the flow from 243 heads. I stayed with lift of .515 intake, .522 exhaust since I drive my car all the time and don't want to think about changing springs anytime soon. My 799 heads are mildly modified and the low lift works well with my heads and the rest of my combo; really my problem right now is putting the power to the ground because I have major traction problems every time I put the "hammer" down, but it's fun.
#13
Total lift isn't always "just about valve lift". Many times it's about creating more time to slow the valve down without inducing instability in the system. Also, say a head stalls at .550 lift.......by taking the valve up to say .625 or so, you can keep it in its peak flow area longer AND avoid harmful harmonics and instability in the system. Whereas if you were to take it only to .550 lift, then try to stop it, roll it over the nose, and start closing it again to fast you'd have horrible jerk values. Higher than necessary lift is often a better way to get good "area under the curve" without resorting to unstable velocity/acceleration values.
#14
On The Tree
Thread Starter
Total lift isn't always "just about valve lift". Many times it's about creating more time to slow the valve down without inducing instability in the system. Also, say a head stalls at .550 lift.......by taking the valve up to say .625 or so, you can keep it in its peak flow area longer AND avoid harmful harmonics and instability in the system. Whereas if you were to take it only to .550 lift, then try to stop it, roll it over the nose, and start closing it again to fast you'd have horrible jerk values. Higher than necessary lift is often a better way to get good "area under the curve" without resorting to unstable velocity/acceleration values.
That's right, I forgot the duration for the rest of the lobe is much more than max lift.
#15
TECH Senior Member
iTrader: (4)
I figured. I've been looking at advertised duration and comparing them to .050.
The ls6 cam is 270/277 204/218. That's 66 and 59. I believe the ls6 was good for 100k? So 55 should be pretty good, sticking with 550 lift. I know there is more to it than that, but I'm betting the factory had pretty smooth lobes. So if I increase the adv duration a bit I should be able to go up to 570 lift and be a good compromise.
Trying to get a soft lobe, make good use of the 243 heads AND keep overlap low.....sigh.
The ls6 cam is 270/277 204/218. That's 66 and 59. I believe the ls6 was good for 100k? So 55 should be pretty good, sticking with 550 lift. I know there is more to it than that, but I'm betting the factory had pretty smooth lobes. So if I increase the adv duration a bit I should be able to go up to 570 lift and be a good compromise.
Trying to get a soft lobe, make good use of the 243 heads AND keep overlap low.....sigh.
Definitely understand not wanting to deal with much valve train maintenance.
However valve seals often need attention even in stock engines wtc
FWIW i ran a nasty 49 ramp rate XER lobe cam for 130,000 miles with a couple of valve spring changes and new retainers and valve seals. Even having a shop do new springs, retainers & valve seals once wasn't too bad $700. Another spring only refresh was $400
#16
TECH Apprentice
I read that as well that Comp Cams XE lobe is easy enough on the valvetrain to allow you to do minimal maintenance and be fine. I would recommend the XE lobe for anyone like me that drives their car many miles or doesn't have the time to tinker with their car on a regular schedule.
#17
Here is a decent link to a guy that breaks down the technical into understandable. Start with what is your max air flow for your heads and what is the point of diminishing returns.
#18
#19
Should still be enough duration to keep pulling past 6k even in a 408. If you want torque, that thing will be a beast.
#20
Depends on heads. If heads flow well up to .600 from .550 then there will be gains. If airflow remains the same or drops them no you wont gain power. On most ls2 heads I seriously doubt there will be gains from 550 to 600