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Analyze this torque curve

Old Oct 14, 2008 | 11:35 PM
  #21  
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I say prove it because . . .
I don't need to prove it. I'm speaking to you with my recommendation from almost 10 full years of working on these engines and seeing/learning/experiencing what works and what doesn't.

Nobody can prove something to you over the internet about your own car. Feel free to clone your car, ship it to me, pay to have a custom cut cam of my choosing, ship THAT to me, and I'll gladly "prove" to you that your cam is inadequate and most of your problem.


I'm done here.
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Old Oct 14, 2008 | 11:54 PM
  #22  
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Just wondering.. I have seen this before as to possible bad dyno readings, almost as if there's a glitch i guess you can say with the dyno. And if I'm not mistaken you said the tuner had the same issue with his setup..? Maybe its just the dyno not picking up correct readings down low?? Just chiming in though sometimes I don't even know what I'm talking about! I've been proven to be right and wrong just like everyone else!
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Old Oct 15, 2008 | 12:03 AM
  #23  
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Originally Posted by Gregory
Please see post one.

Duration 250/246
Lift .631/.631
LSA 114 +6 advance
Please see your Sig.
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Old Oct 15, 2008 | 12:36 AM
  #24  
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Originally Posted by Gregory
It's cool and easy to say "it's the camshaft," or "it's the FAST intake," but can anyone explain why? So far nobody has, it is all just speculation. Heck, it is easy to suggest things for other people to spend money on, but establishing proof is where the rubber meets the road. Just because three out of four people agree on something does not make it fact.
It's the FAST because of the design of the intake runner length, the taper, and the cross-section. The proof is that every single LSx engine running catherdral port heads peaks at 4800 for torque and 6300 for HP. To acheive your best results, you must run a camshaft with an IVC (intake valve closing) that does not fight the natural harmonics of the intake manifold. Sure, you can go really high on your IVC and lose all kinds of torque and make no additional power (plus kill your DCR). But, your IVC of 53 degrees (at .050" lift) is actually about right for the FAST (46-48 for a 346 for max effort, 50-52 for a 383, 52-54 for a 402, etc), which is why it makes good power. But it is designed for max effort.

I will say this: LSx engines are not very sensitive to exhausts as long as they remotely do their job. Changing the cam profile of the exhaust, headers, etc does little to affect overall power on the LS-platform. It can affect overall power output or low-range torque. But, the biggest influence for an exhaust is the exhaust valve and exhaust port on the head, but having an adequate exhaust allows for a reverse split cam to perform very well.

I wouldn't change anything. The torque curve is right.

Last edited by JakeFusion; Oct 15, 2008 at 12:41 AM.
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Old Oct 15, 2008 | 07:36 AM
  #25  
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Originally Posted by JakeFusion™
It's the FAST because of the design of the intake runner length, the taper, and the cross-section. The proof is that every single LSx engine running catherdral port heads peaks at 4800 for torque and 6300 for HP.
It is NOT the intake. I've got graph after graph of cars with LS6 intakes, and even L76/LS3s with the same dip, or lull. They ALL have 2 things in common.
1: the bigger the cam, the more pronounced the lull.
2: If they are ETC cars, i.e. Vette/GTO, the lull is more pronounced.
Seems that for whatever reason, the Fbodies don't show as drastic a lull, setup for setup.

Now, this is basically the same thing you'd "feel" in an old school, gen 1 SBC with a big cam and open plenum manifold. The open plenum is known for killing low end torque, and really "waking up" on the top end. You can feel them come on. It's like flippin a switch, hittin the noz, whatever you wanna call it.
Same with the cam. Too big a cam kills the low end, and comes on strong at a certain point.

Change that gen 1 intake to a dual plane, and you cure some but not all of it. Change the camshaft, and you can make the same engine pull smooth and hard from just off idle to whatever. You'll obviously give up peak, and drop it down some in the rpm band, but you take away that feeling of two completely different power bands. One that's flat, and one that's not.

Depending on compression, and of course the camshaft, alot of times you can tune some or all of it out. If you look at a stock timing table, they have a corresponding dip through the same range. I'm sure others may be able to explain it better, but my take is that the engines peak cyl filling ability is right through there, dictating the need for less timing.

Again I go back to, it is NOT the intake, as I've seen it with virtually every kind of intake available for the LS.
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Old Oct 15, 2008 | 08:21 AM
  #26  
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Originally Posted by Haans249
Please see your Sig.
HAHA! Thats funny! Is the split reversed or not?


...anyways, I remember reading about this torque thing your talking about, but dont remember too much about it. The person that was talking about it was "Patrick G", look him up and ask him this question, he should be able to tell you. Then come back and tell us. What I do remember was that he was saying it was the cam that did that. He explained why, but I wasnt to worried about that part of the thread.

...let us know though!
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Old Oct 15, 2008 | 08:57 AM
  #27  
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Haha, at least all army guys like us have a sense of humor
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