Lobe separation angle 110 vs 114 sound

Hey fellas, some of you are helping me out with my cylinder heads and also chimed in on a side question I had about camshafts and LSA, but I wanted to make a formal thread just to get some facts straight for myself and anyone else taking in the endless amount of camshaft performance and knowledge. Every time you search something about cams you seem to come across somebody asking the experts how to get a huge idle lope and not any loose any driveability or vacuum lol

My first question is, will a given lobe separation angle give you a particular kind of idle regardless of the other cam specs, i.e. lift/duration/ICL. For example, an LSA of 104-107 will be a very rough, choppy idle. 108-110 LSA will be a moderate racey lope, and 111-114 LSA will have a slight lope but a relatively smooth idle.

The more detailed question would be, would a cam with .400" lift and another with .600" lift idle about the same if both were ground on the same (use 108 for example) LSA? OR, another aspect of it, would a cam with 210* duration @.050" idle like a 240* cam if both were on the same LSA?

IF either the lift, or the duration would also impact the idle, how much of either would it take to change it from where the LSA influences it? I hope I'm making sense there.

A lot of guys want a ratty idle and don't wanna do valve springs, pushrods, stall converters or any of the other things that compliment a big nasty cam. For these guys there are the smaller oval track type cams that are limited to a .450" max lift rule, and some are 210* duration and others are 236*, 241*, ect ect. So maybe explain how a 220* would idle different than a 230* or 240* cam. There are also guys who want a big cam but manageable idle, and maybe they could use a wider LSA like 114, but a long duration for that extra power?

My hopes are that this isn't a redundant post, as I've seen many guys asking about cam recomendations who know nothing about engine building but want a snotty idle. Or maybe it'll help the average joe garage builder too, myself included. I'm currently running a Comp 280H with .480" lift 230/230 duration @.050" on a 110 LSA and just received a custom grind in the mail, it's a Comp 282s, which is .495" lift and 236/236 duration @.050", but I had them grind it on a 106 LSA. I have wanted a solid cam for quite a while, and it's a heavy truck so I'm experimenting with a 106 LSA for some low-midrange TQ possibilities. I was curious with both cams being very very similar besides the LSA how they would idle when compared. The 280H is in now, and it has a nice lopey idle and absolutely great power from 3000 on up, and my assumption is that on a 106 it should be a wicked nasty idle and have more umph in the midrange with some TQ.

Thanks to all who jump in and share their camshaft wisdom, I hope this helps some guys pick out a cam in the future

Matt

Table of Contents Show

What is a good lobe separation angle?
What does a higher LSA do?
Is more lobe separation better?
What does 112 LSA mean?

C10matted said:
Hey fellas, some of you are helping me out with my cylinder heads and also chimed in on a side question I had about camshafts and LSA, but I wanted to make a formal thread just to get some facts straight for myself and anyone else taking in the endless amount of camshaft performance and knowledge. Every time you search something about cams you seem to come across somebody asking the experts how to get a huge idle lope and not any loose any driveability or vacuum lol

My first question is, will a given lobe separation angle give you a particular kind of idle regardless of the other cam specs, i.e. lift/duration/ICL. For example, an LSA of 104-107 will be a very rough, choppy idle. 108-110 LSA will be a moderate racey lope, and 111-114 LSA will have a slight lope but a relatively smooth idle.

The more detailed question would be, would a cam with .400" lift and another with .600" lift idle about the same if both were ground on the same (use 108 for example) LSA? OR, another aspect of it, would a cam with 210* duration @.050" idle like a 240* cam if both were on the same LSA?

IF either the lift, or the duration would also impact the idle, how much of either would it take to change it from where the LSA influences it? I hope I'm making sense there.

A lot of guys want a ratty idle and don't wanna do valve springs, pushrods, stall converters or any of the other things that compliment a big nasty cam. For these guys there are the smaller oval track type cams that are limited to a .450" max lift rule, and some are 210* duration and others are 236*, 241*, ect ect. So maybe explain how a 220* would idle different than a 230* or 240* cam. There are also guys who want a big cam but manageable idle, and maybe they could use a wider LSA like 114, but a long duration for that extra power?

My hopes are that this isn't a redundant post, as I've seen many guys asking about cam recomendations who know nothing about engine building but want a snotty idle. Or maybe it'll help the average joe garage builder too, myself included. I'm currently running a Comp 280H with .480" lift 230/230 duration @.050" on a 110 LSA and just received a custom grind in the mail, it's a Comp 282s, which is .495" lift and 236/236 duration @.050", but I had them grind it on a 106 LSA. I have wanted a solid cam for quite a while, and it's a heavy truck so I'm experimenting with a 106 LSA for some low-midrange TQ possibilities. I was curious with both cams being very very similar besides the LSA how they would idle when compared. The 280H is in now, and it has a nice lopey idle and absolutely great power from 3000 on up, and my assumption is that on a 106 it should be a wicked nasty idle and have more umph in the midrange with some TQ.

Thanks to all who jump in and share their camshaft wisdom, I hope this helps some guys pick out a cam in the future

Matt
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LSA itself has a very large impact over very few degrees. 110 is about the cut line between a mild idle and rough to really rough idle. Above 110 you get higher idle manifold vacuum and a smoother idle. Below 110 the idle vacuum falls often quickly and the idle roughens. In simple terms 117 degrees of LSA makes a smooth torque favoring engine especially one that Manifold Absolute Pressure (MAF) EFI likes. Cut that to 107 and you get an engine that idles rough(er), lower torque and not friendly to MAP EFI systems.

How much this affect is seen certainly has a severity linked to durations and lift rates but in general the previous paragraph holds. The greater the duration and the faster the lift rate the greater will be the reaction to the LSA.

Bogie

hcompton said:
Here this should help clear it up.

Technical Specs & Information

To further understand lsa in different cam you got to understand that as the duration goes up the lsa is effected so you cant assume any lsa will act a certain way. at .50 duration of 180 or 280 may have similar lsa but will be a world apart in how a 110 or 104 lsa effects the cam. lsa's effect on the cam does not change but with nearly a 100 degrees more duration the cam will respond wildly different. Since the amount of over lap will be wildly different.

So no way to say that all cams with a certain lsa will act one way.

One way to see this and possibly give you enough information to be dangerous which is how we all started is to look at lunati's site and at there solid lifter cams the drag race series the oval track series and the factory muscle series can show how lsa and duration along with intake center line can change drastically as duration goes up and the intended use of the cam changes. many factory cams are aggressive but also had to work on the road and be used by the public. So in most cases the factory muscle cams sold by lunati will idle under 1000 rpm and have enough vacuum to work accessories. Now one thing to note is these also dont always make good power since they are also made to be easy on the valve springs so ramp rates can be very low.

I know i just made you more confuses than helped but hope this helps.
Click to expand...

Great info! This is what I was hopin for.

64nailhead said:
Comp Cams make a series of cams that are all noise and no go, the Thumper series that are marketed to be noisy at idle. But the end result is a loss of performance (the all noise and no go thing.) Getting a cam to idle, be driveable and be noisy/lumpy sounding is an oxymoron.

My opinion, lumpy cams should come with lumpy cam performance which doesn't include great drive and idle characteristics. And buying based on noise rather than performance is a bit silly. Picking a cam should, repeat should, involve picking one that is designed for your build in terms rpm range, vehicle weight and application. And there is so much more to cam selection than LSA and duration that picking a cam based on those alone is virtually fruitless (ask me how I know.)

Lastly, I don't recommend cams, but there are oters here that do and some of them actually do it for a living. But I do recoomend not picking a cam based lumpiness.

Good luck - Jim
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I'm with ya on cams sound matching the performance level, I wouldn't run a Thumpr if you have it to me for free lol this thread is mostly to gather info on cam specs and find out the effect a given LSA has on different types of cams.

hcompton said:
so if the lift is lower or higher the overlap can change while the lsa stays the same.
Click to expand...

You mean duration more than "lift"... longer duration makes for wider lobes, so more chance of wider lobes overlapping on the timings graph at a given LSA...

And shorter duration is narrower lobes, so they are less likely to overlap...

Picture of the interplay between duration and LSA: LSA is how far the tops of the mountains are apart... DURATION is how wide the base of the mountains are... obviously, narrower mountains can be closer together without overlapping... wider mountains more likely to overlap... overlap, having both valves OPEN at the SAME time just as obviously has a big effect on cylinder pressures at low RPMs/idle... a major AIR LEAK going on... loss of vacuum... rough idle... At higher RPMs, airflow dynamics are taking over... no big power until that happens... the bigger the duration, the more RPMs/speed needed before air flow dynamics takes over...
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More overlap (tighter LSA) improves total area under the torque curve. Typically it does this by creating a larger hump in the midrange. This is created by utilizing charge scavenging/resonance to improve efficiency in a narrow rpm range.

The drawback is off idle performance is sacrificed, this loss is more than offset by the area increase so there is a net gain.

There is no one who drives dyno graphs around and how this tradeoff affects typical driving performance is usually negative, it sucks in traffic and makes it difficult to tune with reversion effects never mind completely incompatible with emisson control or catalytic converters.

Your choice to shorten LSA to increase torque is incorrect, what you will experience is less off idle torque not more. From 2500-4500 rpm you may see a gain and it may be faster on a track but you will need more gear multiplication to offset the torque loss down low.

Widening the LSA will flatten the torque curve and spread it lower/higher in the rpm range. On the street with no other changes, wider LSA will have better manners, be easier to tune, idle smoother and have more off idle torque with a slight loss of total torque under the curve.

Without exception those who I have converted to wider LSA cams say they enjoy their vehicle more and experience superior street performance without having to change gear ratios to use the power their engine outputs.

The problem I see is magazines push the race idea of area under the curve, great for a trailer queen or those willing to sacrifice for a radical idle to get a sound but not one ideal for anyone who wants to drive their car in traffic or maximize economy on the interstate/highway.

My guess is you will be disappointed like many others, most people make this incorrect decision in the beginning of their engine building experience and eventually learn to ignore what a magazine says or what a dyno sheet shows above 3000 rpm...let's face reality once your in top gear your way under this rpm and the reversion from the intake makes tuning impossible without compromises and cold starts a non-turnkey affair.

Trading driveability for curve area is only reducing torque in other areas, yes there is a net gain and an efficiency boost but it's narrow and never where you need it on a street car unless you drive like every light is a tree and your trips are a 1/4 mile long.

36 sedan said:
Confused, isn't overlap and lobe separation essentially the same thing?
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Definitely not, but if you read magazine articles and listen to 'internet experts' then you're going to be lead astray.

Someone else has already explained the meaning of the terms. But as the duration increases with the same lobe seperation angle, then overlap increases. Basically a square 268 cam with an LSA of 114 might have less overlap at .050 than 240 cam with 110 LSA. And picking a cam based on LSA and overlap is a mistake IMO. Cam timing events coupled with compression, application, ramp rates and duration are WAY more important. I've witnessed the proof and it is the reason that you'll never see me recommend a cam. A cam recommendation that doesn't include intake centerline along with duration and LSA is a stab in the dark. That's what you pay a cam grinder for - his expertise and knowledge.

From my personal experience, a member here (cam grinder) ground a cam for me that has 20 degrees less duration and .050" less lift, and ICL that I would've never chosen that outruns the previous cam by 75 HP, has better throttle repsonse and builds boost to 14 psi in less than 1 second of WOT from any RPM between 1800-3500. We went from just under 400whp to 475whp WITH A SMALLER CAM!!!!

I think this explains why I don't recommend cams.

4 Jaw Chuck said:
More overlap (tighter LSA) improves total area under the torque curve. Typically it does this by creating a larger hump in the midrange. This is created by utilizing charge scavenging/resonance to improve efficiency in a narrow rpm range.

The drawback is off idle performance is sacrificed, this loss is more than offset by the area increase so there is a net gain.

There is no one who drives dyno graphs around and how this tradeoff affects typical driving performance is usually negative, it sucks in traffic and makes it difficult to tune with reversion effects never mind completely incompatible with emisson control or catalytic converters.

Your choice to shorten LSA to increase torque is incorrect, what you will experience is less off idle torque not more. From 2500-4500 rpm you may see a gain and it may be faster on a track but you will need more gear multiplication to offset the torque loss down low.

Widening the LSA will flatten the torque curve and spread it lower/higher in the rpm range. On the street with no other changes, wider LSA will have better manners, be easier to tune, idle smoother and have more off idle torque with a slight loss of total torque under the curve.

Without exception those who I have converted to wider LSA cams say they enjoy their vehicle more and experience superior street performance without having to change gear ratios to use the power their engine outputs.

The problem I see is magazines push the race idea of area under the curve, great for a trailer queen or those willing to sacrifice for a radical idle to get a sound but not one ideal for anyone who wants to drive their car in traffic or maximize economy on the interstate/highway.

My guess is you will be disappointed like many others, most people make this incorrect decision in the beginning of their engine building experience and eventually learn to ignore what a magazine says or what a dyno sheet shows above 3000 rpm...let's face reality once your in top gear your way under this rpm and the reversion from the intake makes tuning impossible without compromises and cold starts a non-turnkey affair.

Trading driveability for curve area is only reducing torque in other areas, yes there is a net gain and an efficiency boost but it's narrow and never where you need it on a street car unless you drive like every light is a tree and your trips are a 1/4 mile long.
Click to expand...

I think choosing a narrower LSA cam just for TQ would be a mistake in my position as well, but a lot more things are in play besides a desired LSA and want for more TQ. I think the cam will do really well with my combo, not worse. I have the compression, its 10.3-1, and the stall is 3000 rpm, a 3.73 rear and mini spool so the truck is definitely set up for this cam. It's driven every once in a while for fun when I wanna buzz into town and as soon as the brakes are done it's going to the track.

I definitely agree that a 106 LSA is going to be a little more ratty than the 110 that's in it, but we're talking a 236 cam here, not 240 or above. The Holley 750 DP is great for a ratty cam because you can dial in the tune to be very driveable, and it has a MSD pro billet HEI with springs and weights set up to make a bigish cam run just fine. Let's face the face that reversion and mpg and everything else that goes along with a big cam isn't really a concern when you're building a for fun hot rod, and emissions/catalytic converters are even further out of the question on something that has long tube headers and 3" exhaust with bullets.

I get what you're saying, and I'm sure that people who don't work on their own stuff should avoid something that takes a little finesse to tune, but I highly doubt that I'll be disappointed or learn a hard lesson. Lots of 106 cams on the road and track makin a butt load of power and soundin great, I think my big ole heavy C10 will be another. 106 cams have definitely been proven to work well in heavier vehicles

What is a good lobe separation angle?

Some engine specialists refer to it as that 106 sound—the NASCAR and short track oval sound where preferred lobe separation is usually specified between 104 and 106 degrees. The primary function of narrow lobe separation is to impel urgent acceleration off the turns when the throttle is opened.

What does a higher LSA do?

A wider LSA moves intake- and exhaust-valve events farther apart and creates less overlap, which hurts intake-wave tuning. "When you've properly tuned a performance motor, you create high- and low-pressure waves in the intake and exhaust that help cylinder filling," said Comp Cams' Billy Godbold.

Is more lobe separation better?

“On a naturally aspirated engine, the lobe separation angle has an effect on whether the engine reaches peak torque a little earlier or later in the rpm range. Typically, narrower lobe separation develops peak torque at lower rpm and widening the separation tends to build peak torque higher in the rpm range.

What does 112 LSA mean?

As you suspected, the cam is ground with a 2 degree advance with a LSA of 112 degrees. This means that if you were to degree the cam, you would find the intake centerline would measure 110 degrees BTDC. In this case, there is no reason to further advance the camshaft because the factory has done it for you.