What does this mean?

 

It is the number of degrees between the nose of the exhaust lobe and the intake lobe. Basically it is a measure of how much valve overlap you have. This is also controlled by duration of course. LSA is one of the main factors in how a car idles. If you have a low LSA, like 106 or 108 your car will idle really lopey and have low vacuum. With a high LSA it'll idle smoother. Computer controlled vehicles tend to like higher LSA better. 112 is a good number for a computer controlled engine, IMO.

 

Thanks. my new cam is .473 lift 212 dur @ .050 and 111 lobe sep. hope it works OK.

 

Who makes the cam? That'a a short duration for that lift. It'll really snap those valves open.

Unless what your using a 1.6:1 ratio to come up with that lift? Then that would seem more likely. Then that calculates out to a .442" lift using a 1.5:1 ratio. That duration is more fitting for that lift, especially for a budget cam.

Also with a Chevy engine, you may benefit more from a dual pattern cam.

But if you already have it.......then never mind.

AJ

 

the .473 lift is with 1.5 rockers. the reason for the short duration is to be computer friendly and for more low end torque. I rarely drive over 5000 rpm .therefore I prefer more low end than top end. by the way what are stock rockers, are they a true 1.5

 

That duration is fine since it is a roller cam. You are putting it in a 305, I assume. I put SLPs .480 .487 lift 206 212 dur 110 LSA in my 305 TPI. Unfortunately it didn't help at all; my mph stayed the same and I lost a tenth. The general consensus was that I had more lift than my heads could flow. If I could do it again, I'd have used a cam with less lift, like a stock LT1 cam.

 

The LSA also effects gas mileages as well. with a higher LSA (112 -114) you have LESS overlap....meaning the exhaust valve is closed more when the intake valve opens so less fuel is being allowed to escape the combustion chamber through the exhaust valve before it fully closes. With a lower LSA you have more overlap meaning the exhaust valve is open more when the intake valve opens so more fuel is being allowed to escape through the exhaust valve before it is fully closed.

In addition, TPI like lots of vaccuum for some reason and I don't recommend running any cam with an LSA below 112. The smaller duration/lift cams only need about 112 degrees LSA but once you move up into the .460 lift and 220 duration range the cam should have a 114 degree LSA. Lingenfelter likes 113 degrees with all his cams. Of course lingenfelter also likes 2.00/1.55 valves on heads too.

 

Now how do you know that?

No where does he say it is...he hasn't even said what brand the cam is.

First of all, you're assuming that it's being put in a 305. Second, you're assuming that it's a roller cam.

Athough I did assume it was a flat tappet cam. (opening mouth, inserting foot) Whoops....

I guess we can't find out everything we need to help this person if we start assuming stuff.

---------I would also like to suggest that you (ViciousZ) chose a cam with too much duration, and too close of a LSA, instead of too much lift.

Obviously those are related to each other, but increasing the lift of a cam doesn't nearly effect the power as much as duration and LSA do. Put 1.6:1 rocker arms on a stock cam that came with 1.5:1, and it's still gonna be a weak cam. Know what I mean?

Plus a cam really only moves the RPM range that the power is used in. The more aggresive you go with duration, lift, & LSA, then the higher the "usable" RPM range goes. If you don't use heads, an intake, and exhaust to allow that cam to do what it was made to do, then all it'll do is move the power band up into the RPM range. And probably drop your low end torque. And maybe even loose HP if you go too aggressive.

If you ever look at the graph that a dyno prints, and start out with a stock cam.......then switch to a more aggressive aftermarket cam......then the torque will increase, but usually at a higher rpm. Same with HP. But that's only if the heads, intake, and exhaust will let it.

Sometimes you can compensate for that by moving the intake centerline, but only within the limits of the old "valves slapping the pistons" That's never good.

A cam is so complex that I shouldn't even say why your cam caused you to loose ET. Everything in an engine has to be matched. And then the drivetrain has to be matched to that.

I dunno. This is one of those topics that could go on forever. It's something that no one has figured out yet. If they had, then everyone would be doing the same thing, and how much fun would that be?

AJ

 

Just a clarifiction of something posted above............

Lobe separation is the number of degrees between the CENTERLINES of the intake and exhaust lobes of the cam, not necessarily the noses of the lobes. The point of max lift (the nose) is not usually equal to the centerline of the lobe.

Which begs the next question..........So what's the centerline? It's the 1/2 way point (in degrees) from where the cam lobe just starts to lift the valve from it's seat and where it just puts it back down on the seat.

It's a pretty minor point, really, but I'm sorta **** about cam specs.

 

AJ92RS, yeah, I was assuming, seeing as how his sig says 91 305 TBI RS. And that cam is a good size for a 305. And the duration is realistic for a roller cam with that lift. So don't flame me when you're the one pulling your foot out of your mouth. I said 'assume' in a 'correct me if I'm wrong' manner.
And by the way, my cam was recommended by SLP for a lightly modded 305 or a stock 350. And since you have no idea what my setup was, aside from the displacement, who are you to judge?

 

Since this topic has to do with cams I'd just like to say that I think any cam not made by Comp Cams sucks. Specifically CRANE cams.

 

If you'd read my post more in depth, instead of flaming at me (which you're the one flaming, not me) then you'd see that I did state that I was the one who was opening MY mouth and inserting MY foot!!!!!!

"Athough I did assume it was a flat tappet cam. (opening mouth, inserting foot) Whoops.... "


And I also said later "A cam is so complex that I shouldn't even say why your cam caused you to loose ET."

Obviously you didn't do well in English class!!!!!! You need to learn to read!!!!!! Idiot!!!!!

And I was just trying to help colincamaro, and you were the one that stated that you're car went slower after the cam swap, so I thought I might try and help you!!!!!! If you don't want help, then don't post your problems!!!!!

AJ

 

What are the lobe separations on teh Comp XE series, like the 256 grind and the 262? I heard I should get the 256 if I have stock heads, which I do, but I want something that lopes a little, like, that "daniel Burk" guy on the sound page, his lope is real nice and he has the 262, but I have stock heads, stock everything, soon hopefully some hedman headers and a hooker cat-back. I heard a summit 204/214 cam woudl be nice, it has a 112 lsa. Also, anotehr question, what is lift, what does it do and mean? How do you figure out what lift is right for you engine?

 

Dude, don't you know better than to ask a valid tech question, when those who are replying are getting into a pi$$ing contest?

 

Damn dude, settle down..don't rip the man's head off. It's the holidays for crying out loud

 

ok...once again

What are the lobe separations on teh Comp XE series, like the 256 grind and the 262? I heard I should get the 256 if I have stock heads, which I do, but I want something that lopes a little, like, that "daniel Burk" guy on the sound page, his lope is real nice and he has the 262, but I have stock heads, stock everything, soon hopefully some hedman headers and a hooker cat-back. I heard a summit 204/214 cam woudl be nice, it has a 112 lsa. Also, anotehr question, what is lift, what does it do and mean? How do you figure out what lift is right for you engine?

 

OK, ok I'll answer your question
I actually don't know off the top of my head. I can tell you that you'll find out all the info you need on their website
www.compcams.com

 

Originally posted by 89ROC:


LOL , actually I'm a woman, thanks.

 

http://www.compcams.com/catalog/056_057.html

That page has the specs on that whole product line.

As to more general questions about what the various specs mean and what they do to the way an engine runs, go to http://www.compcams.com/catalog and start at pg. 7 http://www.compcams.com/catalog/007.html and the next few pages. Read some of the other sections, about springs and push rods and rockers, they're quite informative.

 

Welllllllllll............. She never asked for your help and nowhere does it say that you had to 'help' her out with her problems..... And if you truly cared enough to help someone and not just take an opportunity to yap, you wouldn't have opened up on her in the manner you did. Just chill out next time when you are trying to help some one.

 

 

First off I appologize for blowing up. I'm sick (cold) and groggy.
I am sorry.

The only reason I tried to help was that she's under the impression that the lift is what effected the loss in ET. Well I was just trying to explain that duration, LSA, and intake centerline have more to do with that than anything.

If SLP suggested that it's the cam that she should use, then they may have thought that more mods were in the furture. That's all.

BTW, Nowhere did I "yap". I don't post responses on here for that reason. I do try and help. Unfortunatley I was caught on a bad day. AND I DO CARE!!!

AJ

 

WOW, THIS TOPIC GOT REAL INTERESTING. I'LL CLEAR THE AIR ,THIS IS A .473-212DUR.@.050-111 LSA DUAL PATTERN ROLLER CAM DESIGNED FOR A HIGH PERFORMANCE APPLICATION ON A 5.7 BUT WILL BE GOING IN MY 5.0 WITH HEADS/HEADERS/INTAKE/ETC. HOPE IT WORKS OUT, I'M TOLD BY THE SHOP -DELTA CAMS- THAT THIS IS A GREAT CAM FOR A FI CAR.SO NOE THE FACTS ARE OUT, SO WHAT DO YOU GUYS & GALS THINK.

 

Easy on the caps...... But I just want to clarify that the cam you have posted about would be a single pattern cam as it has the same duration and lift for the intake lobes as it does for the exhaust lobes. A dual pattern cam would have different durations and lifts for the intake lobes versus the exhaust lobes. Generally speaking, a single pattern cam will work the best with a high quality - high flowing head. It sounds like it should work fairly well with your setup but I have to suggest that you get 350 or larger engine as you will kick yourself later for spending all of the time, money, and effort on that 305.

AJ - no prob. Everyone has bad days. You are a better man than most for apologizing.