ok, this is what I know. Wider lobe seperation equals less overlap and power tends to be better in the lowend, narrow lsa equals more overlap and power moves up in the rpm band and a loss of low-end power, right? Sooo.... what effects do higher/lower duration/lift have on the powerband? can you use wide lsa for the lowend and then use the dur/lift for the high rev power or vise-versa? I realise this would cause some cancelation on both ends, but should yeild a pretty flat torque curve?

LSA seems to be chosen based on flow capabilities of the heads? Are duration and lift based on cubes, or bore, or stroke? or is this all wrong? I just cant find anything that goes into this kind of detail anywhere on the net!

How about cam degreeing? Base circle? Ramp angle? Did I miss anything?

Sorry, but I really want to understand all of this?

Am I going over the deep end?

 

No your not losing your mind. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> Actually it's a good post and I'm interested in hearing the answers because I'd like to have a better understanding of some of these things too.

 

I'll give this a shot. Someone else will come along and trump me I;m sure.

Someone posted this earlier, so I'll pass it along:

http://www.geocities.com/d_payton1/cam_info.html


*** Well, I started to answer, but there are lots of questions in this. Before I got done, I was doubting myself.

Take a look at the Intake Closing section on that link. Most car guys are shooting for 44 ABDC. Advancing it more may produce more torque (to say 42). You can calculate this by taking your intake duration # then dividing by 2. Add the Intake Centerline. Then subtract 180 from that number. (Intake Centerline is the LSA minus the advance)

Example - Comp 218 cam on a 114 LSA and 2* of advance. (218/2=109) + (114 - 2=112) = 221 - 180 = 41 IC.

So the more duration you have, the smaller the LSA & more advance needed to keep inline with the 44 IC.

Also note the first line or two on Duration.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 99 LM7:
<strong>
Am I going over the deep end? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yes

 

WOW! thats a hell of a lot more info than I have been able to find anywhere else. I'm not sure I understand it real well yet, but it sure does help a whole lot. Thanks a bunch BigTex!

 

No problem. For a pretty good basic look at how camshafts work, look here:

http://www.howstuffworks.com/camshaft.htm

Also, do some searching over in the internal engine section. Lots of good info there.

From what I have learned, to keep a good low end and still make power, you will want to get a little more lift, keep durations down some, get aggressive lobes (so the area below .050 is open a shorter amount of time), and work the LSA and advance / retard properly.

 

yeh, i've read that one and the one at comp cam's website. All I got from either one of those was the whole idea of overlap and where more or less overlap will make its power. Comp's was a little better but not real clear for someone trying to learn more than just the basics I think. So, are you saying that if I went with near stock duration, more LSA, more lift, with a more agressive ramp, I should be able to improve power through the entire power band? I'm really not interested in reving much past the 5500 the superchips has me at right now, so I want all my power under that, say between off idle up to 5500 <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> . Is that powerband workable? What cam spec do you look at for getting a more agressive ramp? The advance/retard would have to be a part of the grind for our trucks, right? Is the cam timeing adjustable on a 5.3?

Sorry I'll save the rest for another post <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" />

 

By the way, can anyone post a comparison of the 99' cam with the 00'+ cam? (00'-03' are all the same right?).


Oh, also, what are the advantages of split duration/lift?

in the internal engine section I see some of the car guys are using 5.3l heads. are they talking about the same heads on the truck engines stock?

 

5.3 heads on a LS1 gives them higher compression - more power.

A traditional split duration is done to account for the restrictive factory exhaust. More exhaust open time to assist the gasses in exiting the chamber. If you were to really open up your exhaust, you could move to a single pattern like many car guys do. Forced induction and nitrous like those patterns as well.

Take a look at comp cams smallest off-the-shelf LS1 cam. It has low lift, but the durations are small and it should make good power on a 5.3. For the price of a new one, you could get a custom grind done. $399 in the sponsors section - Texas Speed and Performance.

If I were to get a mild torquey cam for a 5.3, I might get a custom comp grind 206 / 210 .525 lift on a 114 LSA. Then use 01 LS6 springs. Not sure about advance on that size.

 

Ok, somewhere near $400 for a custom grind or off the shelf. How much would a set of LS6 springs run me and where to buy? Anything else major to buy?

Would the advance (lobe centerline) be something they would do during the grind (position of cam bolt holes?), or is that done at install (changing where the cam gear and cranck gear teeth line up)?

Thanks alot for all the help. I think I have a much clearer picture on this whole cam thing. That 'cam guide' link was realy helpfull.