What real difference does the lsa on a cam make?

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Rockerdude

Rockerdude

Rock n' Roll and A-bodies
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Hey guys, Im getting ready to send my magnum 5.2 cam reground at a cam grinder tomorrow, and I was wondering what lobe separation I should change to. I think stock is 114, I was thinking going to a 110 or a 108 for a cool idle. What else does the lobe separation on a cam effect? Thanks!
 
Lobe sepsration is an advanced description for overlap.If you take a cam on a 112,and grind it on a 108,you add more overlap,the time the valves are both open.Narrower lobe centers mean more low end and midrange torque,along with a peakier powerband,and a slightly rougher idle.Tradeoffs are sensitivity to octane ratings,total timing, and air fuel ratio.A lot to swallow I know,hope this helps you.
 
Bigger LSA = less overlap: Smoother idle, more low-end torque, better fuel economy.
Smaller LSA = more overlap: Rougher idle, more high-end RPM, poorer fuel economy.
 
Alrighty, what would you recommend for my combo? It's a 96 5.2 Magnum, stock Magnum heads with some slight porting, an air gap intake, 600cfm carb, duel 2 1/4 pipes out the back, built 904 with 25-2800 stall converter, possibly 100 shot of the bottle down the road.. The specs I was thinking were 224 duration at .050 lift and .496 lift with the 1.6 rocker arm. And lsa around 112.
 
I install a Crower 34116.114 lobe center,224@ .050'.491 lift, single pattern.Mine idles @ 800,with 21" of vacuum.(5.9).Sounds like a stock 340 cam.You will have your slight idle.The trick is pop for the hughes retainer/spring combo(150,yes pricey).Stock Magnum heads peak .475 to. 490 lift.I spent 299+ tax,if you order online,free shipping.Good luck,love the wagon.
 
Generally, a tight LSA will result in more PEAK HP and TQ, while a wider LSA will result in a little lower number for both, BUT also offer a much broader HP and TQ curve. Generally, with a street driven car, you will want some width to the LSA. Comp settled on 110 pretty much across the board and although sometimes I make fun of it and call it "cookie cutter" it's actually a very good compromise. I discount everything about idle quality, because for me, what's important is how it effects the way the engine RUNS, not SOUNDS. Also too, duration @ .050 has an effect on everything too. It all pretty much boils down to what you want to do.
 
Rockerdude said:
Alrighty, what would you recommend for my combo? It's a 96 5.2 Magnum, stock Magnum heads with some slight porting, an air gap intake, 600cfm carb, duel 2 1/4 pipes out the back, built 904 with 25-2800 stall converter, possibly 100 shot of the bottle down the road.. The specs I was thinking were 224 duration at .050 lift and .496 lift with the 1.6 rocker arm. And lsa around 112.
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With a 112, you can get close to or maybe a touch over 240 @ .050. Remember, this is a roller you're talking about.
 
Is this thing fuel injected?

If so, a narrow center will affect the mixture readings big time in the computer.

Stroker is right, narrow means more peakier HP and TQ. High compression will have issues with fuel octane with a narrow center too. I know it sounds funny, but a narrow LSA builds more cylinder pressure.

I like narrow centers, but it's me, and I can tune around them. Stroker is right, for joe blow, 110 is perfect, 114, to me, is just way too far, but if you do have EFI, (i seen it mentioned) unless you build a sim for the 02, or have something re-programmed, not only are you going to have a quick building compression engine, but also a lean running engine, because narrow center cams are stinkier.
 
Magnums,with stock heads and comp,kinda locked in.Maggies make their h.p. by velocity and reduced bob weights and smaller ring drag. If swapping heads,bumping compression,then it makes sense.Thede Mags peak by 5300 with stock cams.The compression and airflow will not support a narrow lobe center.l
 
As long as your carbureted the tighter lobe centers will give you mid range power. I've built many engines for street only where you wouldn't blow the tires off and didn't have a big top end, but the street range of say 20-80 mph would be extremely strong.
 
I though LSA was built into the blank, ie you can't regrind to a new LSA? Or am I thinking cam centerline?
 
In this case,yes Dodgetk boy. These Magnums are 8.8 to 1 ,real world.These are fantastic engines as stock,or head or cam swap.The E.T.killer is LXguy.He runs 11.70s with a stock short block,on a110 l/.c.
 
I'm just looking for a nice street cam that's better than the stock specs. I'm probably having the heads milled a bit to bump the comp up. Also a while ago, a friend of mine had a cam in his 302 mustang that worked very well with what he had, he specs were 222/222 duration at .050 and .498/498 lift with a 110lsa, but it was a hydr flat tappet. I wanted to match pretty close because I believe that it would be a nice bump up from stock (434 lift, 180ish duration at .050, and 114?lsa). For a mild 5.2 with a 25-2800 stall converter, I think it should be pretty stout.
 
You silly,that grind is a B303 Ford grind.Makes nice power.The catalog says peak torque 3300,peak power 5100.
 
That's the one. This was crane's flat tappet version, that summit slapped their name on and sold off cheap. Lol
 
pishta said:
I though LSA was built into the blank, ie you can't regrind to a new LSA? Or am I thinking cam centerline?
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A good grinder like Oregon cam can put that lobe anywhere on the core they want. I sent them my slant cam that was on a 111 LSA from the factory. Now it's on a 105. I sent them my 331 Hemi cam that was 112 LSA, now it's a 106. It all demends on where the lobes are now and how much meat there is on the base circle. My Hemi cam after grinding has the base circle even with the cam core. It looks funny like some of them early cheater cams, but it's gonna work good. Course I will need different pushrods....and I am gonna run adjustable pushrods anyway so it's no big deal. They told me both my cases were not the norm though. They said that usually the LSA cannot be moved much. Both of my regrinds were exceptions. They are very good at what they do though and I think they were a little modest.
 
dodgetkboy78 said:
BTW, narrow LSA=more low end TQ, not less.
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I assure you, that is not correct. By both experience as well as computer simulation, I have seen otherwise. A 114 LSA compared to a 108 LSA all things equal makes more torque down low on the desktop dyno every single time....without fail. In fact, it's usually a huge difference. The reason for that is because cylinder pressure bleed off is also RPM dependant. The more RPM, the more cylinder bleed off. A wide LAS will build more cylinder pressure down low in the RPM range. They also generally build more pressure in lower compression (under 9:1) engines. I don't know the whys and wherefores, but that much is true. I have verified it in person with a compression gauge many times. The narrow LSA does indeed take away from bottom end torque.
 
StrokerScamp said:
I assure you, that is not correct. By both experience as well as computer simulation, I have seen otherwise. A 114 LSA compared to a 108 LSA all things equal makes more torque down low on the desktop dyno every single time....without fail. In fact, it's usually a huge difference. The reason for that is because cylinder pressure bleed off is also RPM dependant. The more RPM, the more cylinder bleed off. A wide LAS will build more cylinder pressure down low in the RPM range. They also generally build more pressure in lower compression (under 9:1) engines. I don't know the whys and wherefores, but that much is true. I have verified it in person with a compression gauge many times. The narrow LSA does indeed take away from bottom end torque.
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It's hard to say "always" and "never" in these cases. The LSA can be moved by affecting both lobes equally, or each lobe can be moved independant of the other, either advanced or retarded.

RockerDude - there is so much in cam science that the short answer is yes, it can greatly affect power. But in what way, and to what degree, is entirely a matter for conjecture until you have every detail on your specific engine worked out. Talk to your grinder once they have the cam and can tell you what the limits are, and then work with them on it. I like cams with LSAs of anywhere from 108 to 114. If you plan a small NO2 shot, pick a cam based on NA performance. For what you list, I'd like something in the 112-110LSA range.
 
moper said:
It's hard to say "always" and "never" in these cases.
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Absolutely. I agree 100%. I am only saying what I have seen and done. There are so many variables there's no way to nail it down. But, I'll add this.

This is straight from the Wallace Racing site:

Here is the link:

http://www.wallaceracing.com/cambasics.htm

"The lobe separation angle is basically the measurement in degrees of the angle between the intake and exhaust lobes, and is generally between 104 and 118 degrees. This measurement may also be denoted as the lobe displacement angle. Intake and exhaust duration along with the lobe separation angle and camshaft lift combine to determine the amount of overlap, which is the amount of time in which both valves are open. Excess overlap can hurt low rpm performance, and will cause an engine to idle poorly. However, in some engines large amounts of overlap can help high rpm performance by scavenging the cylinders and improving volumetric efficiency. Assuming the lobe separation angle remains the same, the more lift and duration a camshaft has the more overlap it will have. A greater lobe displacement will decrease the amount of overlap, lift and duration being the same. Generally, smaller lobe separation angles cause an engine to produce more midrange torque and high rpm power, and be more responsive, while larger lobe separation angles result in broader torque, improved idle characteristics, and more peak horsepower."
 
I've also read the Comp Cams site about all of this......I gotta say, I firmly believe they got a lot of it WRONG. Most of what they have on it is completely backwards.
 
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