Camshafts: All else being equal, what does an increase in LIFT have on performance?

[Kern Dog]

Lets say you have two camshafts with identical specs except the lift.
Same duration, same intake centerline, same lobe separation but one has say .480 lift and the other has .520. What does the additional lift do for performance?
A quickie Google search has evolved (or DEvolved) into experimental AI which could be good or bad, but it stated that higher lift makes more power but primarily at high rpm. It stated that torque was often negatively affected while high rpm was increased.
That seems incorrect to me as that sounds more like the effect that duration has, not lift.
The old fashioned Mopar Performance camshafts always seemed long on duration and short on lift, I assumed it was because they figured that their stuff was intended to be used in Mopar engines utilizing the stock rocker arms and that once you get much past .500 lift, the rocker arms are at the limits in terms of contact patterns on the valve stems.
Hughes Engines looked at it the opposite way. Their cams are often long on lift compared to the duration numbers.
What are your thoughts?

 

[66 Sat]

I always thought (in basic terms:
More lift = valves opened more = more fuel/air in, more exhaust out = more power, similar to higher ratio rocker arms.

Longer duration = valves opened longer = more fuel/air in, more exhaust out = more power.

I haven't researched it though, I'm sure there's more to it than that. Looking forward to learning something.

 

[70bigblockdodge]

Lift technically does not effect driveability ( look at all these new engines LS, 3 Gen) they all idle smooth and most are over or right at .500 lift. The idea of more lift at same duration is faster opening and closing of the valve resulting in being open further at any point the duration except for the open and closing points. Valve being open more results in more airflow and more power.
Using David Frieburger's door opening and closing analogy that he did on engine Masters. If the door opens and closes for same length of time(duration ), but opens wider(lift), more stuff can pass though wider open door(higher lift) in the allotted time (same duration).
It basically changes the ramp speed of the lobe, and how fast the valve opens. Putting more stress on lifter to lobes interface, and also all the components on the way to the valve and spring. Roller cam alleviates this stress on lifter but not on valvetrain. OEMs use this to get high lift with smaller duration to achieve smooth idle and be able to spread LSA to reduce emissions and still trap cylinder pressure, but that's a whole different direction.
Hope that makes some sense.

 

[vance.dykes]

see if you can fine the episode of engine masters on cam shafts they have a few on different themes i. e lift and lobe separation and more.

 

[vance.dykes]

 

[vance.dykes]

this one is the answer to your question .

 

[icetech]

It's interesting how smooth the curve is with the solids....

 

[PRHeads]

I’m not going to get into a long winded technical discussion about it, but….
Fundamentally I don’t get too worked up about lift.

I select lobes from families I feel are suitable for the application, and the lift just ends up where it does.

The premise in the OP is rarely the real world though.
In most cases, to end up with more lift at the same duration…….the lobe has to be faster(at least in part of the curve), and I would attribute any potential power gains more to that aspect of the cam than the lift itself.

Back when I was doing a lot of dyno testing, I did the rocker ratio swap numerous times.
It was almost never a silver bullet of power, and occasionally the higher ratio resulted in less power.

 

[j-c-c-62]

The key in this discussion is a cam designed for lower RPM can open faster, because ramps can be steeper. A higher rpm cam has to have gentler ramps to prevent valve float because of the faster speeds that comes with higher RPM's. We are only comparing lifts here, not duration.
Maybe the video's above I did not watch say the same thing, or should?