Originally Posted by blueracer15

Thanks Steve i have played around with the calculator to review Cam timing events which have given me more of an understanding.
In this case a build would help with assisting cam choice so we can use my build as an example,
Solely sticking to the comparison of Low duration, High Lift VS High duration, Low Lift

My setup is
Turbo 5.3
LS6 intake
CNC 243 heads
BTR Dual springs .660 lift
TH400 3000 stall
ford 8.8 with 3.27 rear
~ 3000 lb

There are 2 real cam options out there (not made up numbers)

212/218 .600/.600 112+4 Cam1
224/230 .500/.500 112+3 Cam2

I would say the comparison above would fit my exact question
But what Cam will give a Good performance upgrade and what is not a dog when driving light to light
Of course with a aftermarket cam you would expect to sacrifice something, But buying a full race Cam while using it for street /strip driving is the error most people make
while we also wouldn't expect it to drive like a stock cam w/ stock converter
(i saw a video of a extreme cam, while idle driving slowly it hit so hard that when it lopes the tires actually squeal and it jerked forward )

Compare Cam 1 and Cam 2
Cam1
Would the higher Lift of Cam1 compensate for the less duration?
Would this lift it make it act like a larger duration cam 2? (or more suited performance cam)
Would it be work well with (low speed) city since the duration was lower but lift was higher.
OR
Cam 2
Would the Longer duration lower lift cam be better then Cam 1
Would the lower lift cause the low speed driving to be better then Cam 1

Where would the benefit of one come into play over the other?
Which cam would work well on the street
Not what is best suited for the street, not what cam will act like a stock cam
The overlap difference here is the largest thing.
All other valve events are about 5 degrees more (positive) with the larger duration cam 2

Originally Posted by tech@WS6store

Maybe a disclaimer about that 212/600 lobe not being TSP's?

Originally Posted by tech@WS6store

But Texas Speed has a 212/600 lift lobe that has been suggested here. Thats why i said that.

Youre trying to compare 2 lobes with the same adv duration but more lift? Is that right? Because if so, you know as well as I do thats not how it works though. kind of hard to tell from what youve said.

Originally Posted by tech@WS6store

Your diagram looks like very close adv duration for the lower lift vs higher lift. You know thats not the only way to work that and normally never the way its done.
Matching @.050 duration and adding lift is what we have done on at least 2 cams we have and i can guarantee they are less aggressive than a few other company's with less lift but same @.050 duration.
There are too many ways to engineer a lobe to point at one diagram and say thats it. Especially now with asymmetric lobes, which have been out for years.

Originally Posted by CAMMOTION PERF

Hey BlueRacer15,

Thank you for the question. Being a turbo, it adds a little complexity to my reply, but lets look at your questions:

Compare Cam 1 and Cam 2
Cam1
Would the higher Lift of Cam1 compensate for the less duration?
Would this lift it make it act like a larger duration cam 2? (or more suited performance cam)
This question can be answered in a general way for the sake of this discussion, but I think I can give you more insight by giving you a new view of the relationship between lift and duration. When you listed the duration figures in your post, it looks like you listed duration at .050" of valve lift. When you listed "lift", you are specifying peak lift at the valve. Those are derived from just two points on the lobe. You must ask, what happens to the shape of the lobe when you change peak lift and duration.

As you increase peak lift, the duration of the camshaft at different lifts will change with it (while maintaining similar lobe acceleration rates). We make many different lifts per a given duration at .050". For example. I can make your "224" duration @ .050" lobe with the .500" (with a 1.7 rocker ratio) valve lift you specified, or I can make your 224 duration @.050" lobe with .629" valve lift (with a 1.7 rocker ratio). These two "224" lobes will have the same duration at .050" and I can even give them the same duration at .006" lift, but as lobe lift rises above .050" in lobe lift, the cam lobe with more lift will have more duration.

The higher lift "224" cam lobe will have more duration than the low lift "224" cam lobe at .100", .150" .200" .250 lobe lift etc. This relationship demonstrates that lobe lift actually changes lobe duration depending on where you measure the duration in lobe lift. So, as you can see, we are not just talking about the effects of peak lift. In fact, we are only at peak lift for a blink. We touch peak lift and then the valve starts to close. So, peak lift is not really the effect that matters. What matters is the fact the higher peak lift creates a lobe that has more duration at higher lifts above .050" lobe lift. In this example, our "224" lobe with .629" valve lift (with 1.7 rocker ratio) will have 145 degrees of duration at .200" lobe lift vs 133 degrees of duration at .200" lobe lift for our "224" lobe with .500" valve lift. And, at .300" lobe lift our "224" lobe with .629" valve lift will have 91 degrees of duration at .300" valve lift whereas the "224" lobe with .500" valve lift will have 0 degrees of duration at .050".

Often times you will hear people say something like: there is no reason to have more than .650" valve lift for use with a head that does not flow any more above .650" valve lift. This is wrong thinking. It is not the flow at peak lift you are after, it is the additional duration at lifts between .050" and .650" that you are after.

Would it be work well with (low speed) city since the duration was lower but lift was higher.
OR
Cam 2
Would the Longer duration lower lift cam be better then Cam 1
Would the lower lift cause the low speed driving to be better then Cam 1
Now that I have said what I wanted to share on the relationship of lift, duration and lobe design, I will answer this question more generally to give you a feel of how I look at this relationship. In general, higher lift, shorter duration cams have the potential to produce a better drivability to power relationship. In general increasing lift will increase power and can increase RPM range while not affecting drivability notably. While increasing duration will generally move the RPM range upward and produce more peak power, but will likely diminish drivability noticeably. This is generalizing, so keep that in mind. Now it is time for the BUT..... BUT, there are practical limits to how much lift you can run for a given duration. As you increase lift per a given duration, you also increase acceleration of the valve train. As you increase the acceleration of the valve train, you increase stress on parts and deflection on valve train components. The 212 duration at .050" lobe lift lobe with .600" valve lift that you specified is an very aggressive lobe. To make this lobe, you will have relatively high acceleration rates. For an application like yours, I would limit the lift on a 212 duration lobe @ .050" lobe lift to just under .580" valve lift using a 1.7 rocker arm.

Where would the benefit of one come into play over the other?
The 212/218 camshaft would have a smoother idle, more idle vacuum, get better fuel economy, have better low speed torque, better throttle response and likely spool your turbo quicker. I feel like this would make the general driving experience better.

The 224/230 camshaft has a full 12 degrees more duration. So, the drivability will not be as good. And, while the increased duration has the promise of make more peak power at a higher RPM, the low .500" valve lift will hurt that cams potential substantially. However, because it is a turbo application, the boost will help make the best of the situation compared to a naturally aspirated scenario.

Which cam would work well on the street
Honestly, I don't like either one of them for this application. The 212/218 .600"/.600" has too aggressive of a lobe for this application in my opinion and the 224/230 .500"/.500" has an unnecessarily soft lobe for this application. If I owned both of those cams, I would sell them both and get something better suited. While these two cams serve as extremes for the sake of example, neither one is a good real world choice for your application in my opinion.

Here is a graph of the 212/600 lobe versus the 224/500 lobe:

As you can see, the very low .500" valve lift (1.7 rocker arm ratio) hurts the potential of the 224 lobe pretty substantially when compared to the very aggressive 212 lobe with .600" valve lift (using 1.7 ratio rocker arm).



Here is what happens when you compare a 212 duration at .050 lobe lift with .600" valve lift lobe to a 224 duration lobe @ .050" lobe lift with .629" valve lift (valve lift is using a 1.7 rocker arm)



As you can see, when you give the larger duration lobe a more normal lift, its potential increases substantially. In this case, the 224 lobes .629" valve lift will have less valve-train acceleration and be easier on the valve train the the 212 lobe will at .600" valve lift. The additional duration at .050" lobe lift allows achieve a higher valve lift while creating lobe that will be more stable at upper RPMs.

Time and time again I see cases where to aggressive of a lobe actually hurts power due to the deflection and instability that it causes. Conversely, too soft of a lobe will also leave power on the table. Although, typically I see more people opt for a lobe that is too aggressive.

I want to summarize by saying this. I recommend that engine builders choose a lobe that is appropriate for your valve train and application, then choose your valve events.

~Steven