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I fully appreciate your desire to understand how cams work so that you can discuss your options with a cam grinder.
However, from reading the responses it seems that you would need [almost] infinite time and money, plus variable cam timing, in order to find the absolute sweet spot. Otherwise, there are so many variables that there is little chance for "absolute perfection," whatever that might mean.
Good luck in finding a cam that meets your needs/wants and let us know what you find.
 

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There are so many variables when it comes to designing a cam to fit an engine. Look at these numbers for an LS7 hydraulic roller split cam and look at the separation angle. Then consider the engine makes over 500 HP @ 6300 and usable power to the 7K redline. The car idles so smooth that i can lug it in traffic in 1st or 2nd at 5-7 MPH which is a great thing because otherwise if it bucked the car would be a real pain to drive in traffic. The induction system on this engine flows nearly 300 cfm stock so it definitely can breathe. I'm sure there was a lot of research that went into designing this cam to meet power requirements while still providing great driveability and meeting emissions standards...interesting.

That isn't the only engine that likes wide LSA numbers. A 455 Buick likes 122*LSA . 108 is terrible on one of them. I did a jet boat cam for one back in the '70s and it wouldn't get out of it's own way , but 108 was good in a 460 Ford jet boat. The cylinder heads are the reason in most all of these LSA variations besides type of induction.
I use piston guy as a screen name on Speed Talk.
Randy

Camshaft Part Number12638426
Duration @ .050 in. (int./exh.)210°/230°
Valve Lift0.593 in./0.589 in
Lobe Separation120°
 

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That engine
There are so many variables when it comes to designing a cam to fit an engine. Look at these numbers for an LS7 hydraulic roller split cam and look at the separation angle. Then consider the engine makes over 500 HP @ 6300 and usable power to the 7K redline. The car idles so smooth that i can lug it in traffic in 1st or 2nd at 5-7 MPH which is a great thing because otherwise if it bucked the car would be a real pain to drive in traffic. The induction system on this engine flows nearly 300 cfm stock so it definitely can breathe. I'm sure there was a lot of research that went into designing this cam to meet power requirements while still providing great driveability and meeting emissions standards...interesting.

Camshaft Part Number12638426
Duration @ .050 in. (int./exh.)210°/230°
Valve Lift0.593 in./0.589 in
Lobe Separation120°
That engine seems to support the "big head, small cam" theory of horsepower production.
 

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I fully appreciate your desire to understand how cams work so that you can discuss your options with a cam grinder.
However, from reading the responses it seems that you would need [almost] infinite time and money, plus variable cam timing, in order to find the absolute sweet spot. Otherwise, there are so many variables that there is little chance for "absolute perfection," whatever that might mean.
Good luck in finding a cam that meets your needs/wants and let us know what you find.
You are not alone in that feeling! The reason "I" go into detail is to show what is really important . Having been in the camshaft industry , I know how catalog listings are formulated. Rarely do you find a big manufacturer with a "tech " person that runs what you do , so they often speak in generalities. On occasion , I use a "manufactured" cam but most are custom because I "think" I know better.LOL
 

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FWIW one of the more expensive sumo simulation softwares will runs bunch of cam lobe iterations and pick what “It” things is best. Of course for decent results, you have to
Know all the details of your engine...like head flow, etc...
 

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The guys over at the speed-talk Engine forum are super knowledgeable (many here are also) and several are professionals including custom cam grinders who will answer questions in a very helpful manner.
Speed-Talk, where one situation can give you 3-4 different right answers, all from race proven winners that make a living doing it.
Like ways to skin a cat, you end up picking the one closest to what you thought was best to begin with:)
 

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Discussion Starter #47
So I definitely do understand that LSA is kind of a made up number, just an average of Intake Center Line and Exhaust Center Line so obviously there's more than one way to get the same LSA with different center lines. So my cam has an intake center line of 112 and an exhaust center line of 112 (making the LSA 112). What is a more ideal intake center line for an SBF with Twisted Wedge heads?

I'm trying wade through even just what's on here, it's a lot of info! I understand I will never get the ideal cam without more effort and money than it's worth. Just trying to maybe get some improvement by being smarter about it.
 

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I started to make some calculations to show the relation to valve lift and piston speed and ended up with a crude form of engine simulation tool in Excel

What you see here is the induction process at 6000 RPM of a 289 with stock heads and a 270 deg intake lift profile at an intake center line (ICL) of 106 (solid lines) and 114 deg (dotted lines). In the second graph you see the rate of change of the cylinder volume ("piston cfm") and the flow that the head provides at the usual 28" H2O, which is around 1 psi. As you can see, the demand of the moving piston is much larger than what the head flows at a pressure drop of 1 psi, so the in-cylinder pressure will drop much more than 1 psi (third picture). Due to the much larger pressure drop, the head will flow much more, but still not enough. When the piston slows down, the pressure drop remains so the flow continues almost until the valve closes and the pressure drop is almost zero. The volumetric efficiency ends up being about 72%.

Now, this is a simplified case with continuous flow and none of the fluctuation pressure waves that bounce back and forth in a real intake system. Also, the ram effect of air moving at high speed near the end of the intake stroke and the closing valve increases the pressure upstream of the intake valve and thus the flow is not taken into account. The volumetric efficiency of this engine (like a stock 65 GT350 engine) will therefore be a bit higher than 72% (but far from 100)

The earlier cam phasing can cope with the demand of the moving piston a little better, leading to a lower pressure drop. The cam with the later phasing catches up later, but doesn't quite make it.

764448
 

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Here you see the same engine, but now at 2000 RPM and a 270 deg cam (like in the previous post) and a 300 deg cam. At this low speed, the head flow is more than sufficient and the pressure drop will be less than 1 psi a will the actual head flow. The volumetric efficiency peaks at BDC and decreases somewhat due to back flow until the valve closes, a bit more so for the long duration cam.
764453
 

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Now we're back at 6000 RPM but with a 30% better flowing head (dotted lines), which would be the equivalent of a entry level aluminum head, like a GT40Y or something like that, vs stock head (solid lines). Volumetric efficiency is now up by 25% (from 72 to 90%). Or going from 275 to 343 hp, which is a bit high but not too far off.

764454
 

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Here's a last one:

Same 289, 6000 RPM, stock heads and a 290 cam with a 106 ICL and a 270 cam with a 114 deg ICL. This means that they close at the same time. The lack of valve lift in the early part of the intake process leads to a lack of flow that is not compensated for later in the process.

The next set of graphs shows the opposite. Now the opening is aligned and the initial intake process is the same. Now the long duration cam gains a lot at the end.

764464
764465
 
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