And your not going slow either!

 

Bump from 2006. Thread started in 2001.

 

I frieking love this thread. thanks for the worthwhile thread mining

what about the effects of intake design and firing order on valve events, namely IVO and EVC? Wouldnt firing order have an effect on where partial vaccum would occur in each intake tract? would there be a way to time the valve events to account for this?

 

Tell me about it.... I even posted on this one!

 

Looking at installing ported 243 patriot heads, and a custom grind comps cam 238/242 at .50 and 604 in & 609 ex with a lsa of 115 on a ls2 vette. Already have kooks headers full exhaust with high flow cats, fast 92mm intake, honker cold air box and currently make 410hp & 403tq at the wheels, will this cam work well with my set-up or is it a bit to much? Thanks for the advice guys.

 

It's way too big and way to wide, might make a nice peak number but compared to what you can have it's a POS

 

I do that every now and again. Well, when search worked, I used to do that.

This is one of the all time greats, IMHO. There was another cam thread that I couldn't find I was going to bump that really got heavy. I mean, it was crunchy.

I wasn't posting really at this time. I got on here in late 2002, early 2003 when I had an LT1. Didn't join until after I got an LS1 car.

Good read. Send some of the newbs this way since search sucks so bad.

 

What about intake center line? I've noticed that Comp puts pretty much all of its gen III and gen IV cams on a 109 ICL. Vizard, in his 1992 cam and heads book, pretty much says the same thing, that a particular engine is generally going to like a certain ICL, no matter what duration you use. Therefore, he seems to think duration is secondary to ICL. Or maybe not secondary, but the optimum ICL does not change even when you change duration.

The confusion comes in, in that I see the ICL for the LS cams all over the place, and I don't know if that's because the aftermarket guys are trying to imitate the factory cams, or if they know something I don't.

It would greatly help if anyone knows the ICL of the ASA, stage 2, and stage 3 cams. Anybody?

The idea was that instead of picking a duration and then compromising the valve events to adjust the overlap, I would pick an overlap that I know I could tolerate based on known cams, and then, using the best ICL for the motor, come up with an exhaust lobe profile.

For example, I like the idle on the GM 846 cam for gen I and gen II engines. It has 2 degrees of overlap at .050". Using Comp's default ICL, that gives me a 222/222 cam on a 109 LSA. And there I'm stuck. Seems like everyone puts at least 8 degrees more duration on the exhaust, so I'd have to add that to the opening side of the lobe. That would move the ECL out 4 degrees, giving me a cam that ended up at:

222/230
111 LSA with 2 deg advance.

That seems tighter than most people run. I think that because the manufacturers widen the LSA a bit to smooth out the idle on a cam that someone chooses because of the duration, it has become the trend to assume the wide LSA is correct when it actually isn't.

 

Then, when you think you know everything there is to know about cams, add pressure on the exhaust AND intake side. Holy blown minds, batman! I love threads like this, it exemplifies the statement in my signature. So many people on this site will say "go with a 112 LSA cam, they rock" when they have no clue WHY a particular cam "rocks".

 

+1 on being a good thread, even being 8 years old

 

Camshafts is one of those subjects where the more you know, the more you realize you don't know...

 

Kind of like women... although with enough reading and experimenting, at least you can eventually understand camshafts.

 

In this thread it says the numerically higher the LSA of a cam, the higher it makes power in the rpm range...

I was under the impression that a numerically lower LSA cam (say 108 LSA) is for high end... and numerically higher LSA cam(114LSA) is more streetable, because it makes better low and midrange??

Am I missing something here??

Unless the numerically higher LSA cam is making the rpm range more broad over all(high rpm and lower rpm)..
and if that is the case, then why dont we all just go with huge LSA cams??

I also remember learning about this in 2005 and 2006 and thats what I remember..

weird..

 

The way I understand it, and i'm by far no expert, the 108 split will be less streetable because of higher overlap. The 114 LSA just the opposite -- less overlap.

Otherwise, your understanding is the same as mine; tightening the LSA (making it a lower number) means bringing the powerband down. That helps both street and race cars. On a race car with high durations and overlap, etc., it will still be making its power way up there even with a with a tight split.

That's all as I understand it and I in no way pretend to be an expert at all.

 

On the old technology, single pattern cams, the tight LSA worked. For a street motor, you would use a cam with, for example, 214/214 on a 107 LSA. If you wanted more power, you would keep the LSA the same but increase the duration, which gave you both more overlap and a later closing intake and an earlier opening exhaust, all in proportion to each other. The torque curve didn't change its shape but moved up the rpm band. for the 214/214 cam, the peak hp might have come at 5000 rpm. Changing to a 222/222 might move it up to 5500 rpm.

Then they invented the dual pattern cams. Since exhaust flow was always weaker than intake, by holding the valve open longer they got more rpm out of the engine while maintaining the low and midrange torque.

If I wanted to open the exhaust a little sooner with the 222/222 cam, I could widen the LSA, but that would cut overlap which would hurt top end more than the earlier exhaust opening helped. So if I made the cam a 222/230, I could maintain overlap and still open the exhaust sooner. But that advances the exhaust centerline 4 degrees (because you're adding all the duration to the opening side of the lobe); even though you have the exact same overlap as before, the exhaust lobe is now on a 111 deg centerline, so you now have a cam on a 109 LSA and running 2 degrees advanced, where you were running straight up before. So the LSA is really only a derivative of the lobe shapes and not something that affects the cam's performance in and of itself. It is very useful as a reference point, though, which is why I was trying to understand why these cams have such wide LSA's compared to the old school cams.

 

this thread has been really helpful
a lot of reading tho

thanks guys

 

wow why and when did sstrokerace get banned? we need more experts like him around and have lost quite a few in the last year or two.. any chance of lifting the ban?

 

i think it had something to do with saying not nice things about board sponsors, or maybe that was just another time he got banned. yea bret knows his ****, unless you ask around the lt1 forums where everyone hates him. he spec'd the cam in my motor.