Wider lsa for performance vs tight - Chevelle Tech
Performance Our High Performance area

 60Likes
Reply
 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 85 (permalink) Old Nov 30th, 19, 5:06 PM Thread Starter
Senior Tech Team
 
Join Date: May 2006
Location: SoCal
Posts: 11,204
Wider lsa for performance vs tight

Like to hear from the cam guys/builders for their thoughts on this
We know what tightening lsa up does

Ex 350, 383 454 etc with the typical 10:1, 280 type cam afr type head

Say you wanted something with a 112 over a 108lsa which crower seemed to be fond of yrs ago.

Pros and cons?
know cam timing events are everything but perhaps some examples w a grind that wasnt slamming seats?

Quote:
This post is a duplicate of a post that you have posted in the last five minutes.

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
cuisinartvette is offline  
Sponsored Links
Advertisement
 
post #2 of 85 (permalink) Old Nov 30th, 19, 5:31 PM
Team Member
Mark
 
Join Date: Dec 2007
Location: Tampa, FL
Posts: 1,126
Re: Wider lsa for performance vs tight

I agree with your statement "Cam timing events are everything". LSA should just happen and not drive your cam choice.

Here's my examples:

Ran a 350 for years with all the XE flat tappets. These were all on 110. After the XE274, I tried Isky MegaCams, which were all on a 108 LSA. When I went up to their 230/280 duration version, power brakes were iffy but power was great. Tried to get more idle vacuum with some Rhoads lifters, but they only helped a little. The problem was creeping in stop and go traffic (I got used to shifting to neutral).

Second example was 2 427 sbc's. The first originally had the Comp XE300 lobes on a 108 LSA installed at 104. This cam had a ton of torque and power, but it fell off hard after the 6200 hp peak. The engine shop suggested adding a bit of exhaust duration and keeping the 104 installed but spreading the LSA (to 112) to maintain the same overlap. The engines seems to run very similar with the 112LSA build having just a little less peak torque but similar hp with less loss after hp rpm peak.

I'm no expert, but I think you first figure out what you want from rpm based on how you want to use it. Then you pick heads (and CR). Then you pick lift that makes use of the heads, duration to meet your rpm needs, and overlap to meet your drive-ability needs. The trick (that I don't know) is figuring out where you want the intake centerline. Once you have that, you have everything you need to pick a cam, get lobes on a custom cam, or understand what the engine and cam designers tell you.

69 Chevelle Malibu
427 sbc, TH400, 3.55 12-bolt
n/a best: 11.24sec/118mph
MadmanMark is offline  
post #3 of 85 (permalink) Old Nov 30th, 19, 6:37 PM
Tech Team
 
Join Date: Feb 2019
Posts: 663
Re: Wider lsa for performance vs tight

This year I ran a 105 LCA cam vs. a 114 LCA cam in my BBC engine. The narrow LCA cam ran 2 mph faster and 2 tenths quicker than the wider LCA cam. The narrow cam was choppier and the wider cam had a better idle and cruised better. I was surprised that the wider cam did not make more top end power.
68Chevele is offline  
 
post #4 of 85 (permalink) Old Nov 30th, 19, 8:06 PM
Lifetime Premium Member
 
Join Date: Oct 2005
Location: CT,USA
Posts: 12,775
Re: Wider lsa for performance vs tight

In my experience, with all other things being equal, or close to equal, the tighter LSA will render a narrower power band, (ie. the power begins later in the RPM band, at a higher RPM, and it also ends sooner at a lower RPM) but along with the narrower band of power that the tighter LSA creates, the power comes on more abruptly, and is more intense than it is with the wider LSA.
hydro462 likes this.

70 Chevelle SS clone (632 CI powered).
BillyGman is offline  
post #5 of 85 (permalink) Old Dec 1st, 19, 9:59 AM
Lifetime Premium Member
Tom
 
Join Date: Oct 2017
Location: Traverse City, MI
Posts: 117
Re: Wider lsa for performance vs tight

General rule of thumb where the only change is the LSA - narrow LSA's produce more torque but have a narrower torque band, wide LSA's flatten and spread out the torque curve (less peak torque with a wider band). Narrow LSA's have lower idle vacuum (more overlap), wider LSA's have smoother idle. Wider LSA's require more compression to achieve the same cylinder pressure - intake valve closes later in the cycle.
1975TypeS-3 is offline  
post #6 of 85 (permalink) Old Dec 1st, 19, 3:04 PM
Lifetime Premium Member
 
Join Date: Oct 2005
Location: CT,USA
Posts: 12,775
Re: Wider lsa for performance vs tight

Let me add that what constitutes an LSA being considered "wide" is relative to the rest of the camshaft specs, (especially the [email protected] numbers). For instance: all of us tend to consider a "tight" LSA as being a 106, or a 108 LSA, but that mostly applies to street/strip camshafts with [email protected] numbers in the 230-260 degree or even 270 degree range. But take a look at really big cams with lift specs in the .800+ or .900" lift range, and [email protected] numbers in the 285-290+ degree range. You'll see that ALL of the cams that are that big have LSA numbers of 114, 116, and even 118. And even cams that big with a 118 LSA still create lots of valve overlap.

So in a certain sense,(at least as far as valve overlap is concerned anyway) cams with durations that are that long in essence can be considered having a "tight" LSA if it's 114, as opposed to a 118 LSA. Why is that you say? Because there's only so much valve overlap that can be designed into the cam before the engine just wouldn't run right at any RPM, and a camshaft with a [email protected] duration with a 114 LSA will usually have as much valve overlap, (if not more) as a cam with a 260 [email protected] with a 106 or 108 LSA will. Because with a lobe that has a 290 [email protected] it's holding the valve open so long, much more valve overlap is unavoidable.

That's why you'll never see a cam with a 290+ [email protected] with a 106 LSA or even a 108 LSA. It would be pretty close to physically impossible if you don't want the engine to run terrible at all RPM ranges, due to having waaaaay too much overlap between the intake opening and the exhast valve closing. You can only hold both the intake and the exhaust valves open simultaneously for so long. After a certain point, if you hold them both open for any longer, engine function begins to go south and performance suffers big time

70 Chevelle SS clone (632 CI powered).
BillyGman is offline  
post #7 of 85 (permalink) Old Dec 1st, 19, 3:21 PM
Senior Tech Team
Scott Foxwell
 
Join Date: Dec 2008
Location: N/E Tennessee
Posts: 3,811
Re: Wider lsa for performance vs tight

LSA is not a way to analyze, choose or describe a cam. It's not a "goal" or even a design criteria. It's nothing more than a result of the valve events. It's a by-product. Change LSA and you change the valve events. THAT is what makes the difference. You can change the LSA and not change the overlap, and you can change the overlap and not change the LSA. LSA tells you nothing useful about the cam, just like .05 duration numbers. It's a marketing term that the cam manufacturers came up with.
mr 4 speed and badrad like this.

FOXWELL MOTORSPORTS
Straub Technologies

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
steelcomp is offline  
post #8 of 85 (permalink) Old Dec 1st, 19, 3:41 PM
Lifetime Premium Member
 
Join Date: Oct 2005
Location: CT,USA
Posts: 12,775
Re: Wider lsa for performance vs tight

Quote:
Originally Posted by steelcomp View Post
LSA is not a way to analyze, choose or describe a cam. It's not a "goal" or even a design criteria. It's nothing more than a result of the valve events. It's a by-product. Change LSA and you change the valve events. THAT is what makes the difference. You can change the LSA and not change the overlap, and you can change the overlap and not change the LSA. LSA tells you nothing useful about the cam, just like .05 duration numbers. It's a marketing term that the cam manufacturers came up with.
I understand your point Scott, but with ALL other things being equal on two different cams, both the [email protected] and the LSA numbers being different between the two cams are going to be an indication of how differently the two will make the engine perform. But like you've stated, it will be due to the valve events changing, and LSA change just so happens to also be a result of that.

I was kind of simplifying things to make a comparison, between cams with most or all other things being equal, (like I pointed out previously). I fully understand that things like the [email protected] lift are more indicative of the cam lobe "intensity" how steep the opening ramps of the lobe might be, and of how that cam will cause the engine in question to perform, and I also understand that valve overlap can be designed into the cam lobes almost anywhere that the designer wants to place it at. Again, it was an oversimplification on my part to make a general comparison, without getting too technical. I am not disagreeing with what you said. But I've experimented with cam swaps of three different LSA numbers going into the same motor, without anything else being changed, and I've noticed how it changed the powerband. However, I also will point out that none of those were custom cam designs. They were all off the shelf pieces from the same cam manufacture for street/strip use.

It's merely a generalization on my part, and I know that you would need to look at the valve timing events to make an exact comparison. Thank you for pointing that out
steelcomp likes this.

70 Chevelle SS clone (632 CI powered).
BillyGman is offline  
post #9 of 85 (permalink) Old Dec 1st, 19, 11:39 PM
Senior Tech Team
Dennis
 
Join Date: Jul 2003
Location: kansas
Posts: 2,833
Re: Wider lsa for performance vs tight

Quote:
Originally Posted by steelcomp View Post
LSA is not a way to analyze, choose or describe a cam. It's not a "goal" or even a design criteria. It's nothing more than a result of the valve events. It's a by-product. Change LSA and you change the valve events. THAT is what makes the difference. You can change the LSA and not change the overlap, and you can change the overlap and not change the LSA. LSA tells you nothing useful about the cam, just like .05 duration numbers. It's a marketing term that the cam manufacturers came up with.
I will say the @.050" numbers are a lot better then the crappy advertise numbers ( that was market hype duh!) of the olden days or they real crappy 3/4 or full race cams terms. Your opinion on the @ .050" numbers is a poor opinion. I don't care what your back ground is. The .050" numbers are way better. Your opinion is meaningless. Most know when one is talkin lsa they get what is meant. No need to get so technical you become the azz in the crowd. Like you are. Terms and understanding of cams have gotten better over the decades. In one statement you just threw it all out the window. Bring on the hate, Mr smarty pants.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

pics of projects and whatever.
ddeennis is offline  
post #10 of 85 (permalink) Old Dec 2nd, 19, 3:39 AM
Senior Tech Team
Gary
 
Join Date: Feb 2007
Location: Kansas City,Mo.
Posts: 4,384
Re: Wider lsa for performance vs tight

I kind of agree with David vizard on this subject especially for a street performance cam you choose the lobe separation angle first and the duration required afterward. Generally the more compression higher engine speed and better cylinder heads favor a wider lobe separation angle.
jeff swisher and bradley67 like this.
gnicholson is offline  
post #11 of 85 (permalink) Old Dec 2nd, 19, 8:38 AM
Senior Tech Team
Rick
 
Join Date: Nov 2006
Location: Langhorne, Pa
Posts: 4,223
Re: Wider lsa for performance vs tight

Quote:
Originally Posted by ddeennis View Post
I will say the @.050" numbers are a lot better then the crappy advertise numbers ( that was market hype duh!) of the olden days or they real crappy 3/4 or full race cams terms. Your opinion on the @ .050" numbers is a poor opinion. I don't care what your back ground is. The .050" numbers are way better. Your opinion is meaningless. Most know when one is talkin lsa they get what is meant. No need to get so technical you become the azz in the crowd. Like you are. Terms and understanding of cams have gotten better over the decades. In one statement you just threw it all out the window. Bring on the hate, Mr smarty pants.




So:


At 50 number meaningless, check
lsa meaningless, check


Productive day here on Team Chevelle.

1967 Chevelle Malibu 4 door


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


The 7.99 at 173mph pass:


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


8.02 at 171mph:


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Calculated Risk is offline  
post #12 of 85 (permalink) Old Dec 2nd, 19, 9:10 AM
Senior Tech Team
Scott Foxwell
 
Join Date: Dec 2008
Location: N/E Tennessee
Posts: 3,811
Re: Wider lsa for performance vs tight

Quote:
Originally Posted by ddeennis View Post
I will say the @.050" numbers are a lot better then the crappy advertise numbers ( that was market hype duh!) of the olden days or they real crappy 3/4 or full race cams terms. Your opinion on the @ .050" numbers is a poor opinion. I don't care what your back ground is. The .050" numbers are way better. Your opinion is meaningless. Most know when one is talkin lsa they get what is meant. No need to get so technical you become the azz in the crowd. Like you are. Terms and understanding of cams have gotten better over the decades. In one statement you just threw it all out the window. Bring on the hate, Mr smarty pants.
Hate? Seriously? Speak for yourself. There was nothing personal about what I said. Sorry you took it that way.
So answer this;
What does LSA tell you about a cam? I don't mean some vague stupid internet answer like, "wider lsa makes "this" power, narrower makes "that", I mean, tell me what the LSA of a cam tells you about how the cam is designed. What does it tell you about the valve events?
I have a cam with a 110 lsa. What does that tell you?
How about, I have a cam with a 110 lsa, and another cam with a 108 lsa. Both are .680 lift, .260 duration @ .05.
It tells you NOTHING useful about either cam.
Trying to insult me or put me down and making this personal just tells me I'm right and you don't have a clue what you're talking about. "Terms and understanding" about cams haven't changed in the 40 yrs I've been doing this but the internet has sure created a lot of experts.

FOXWELL MOTORSPORTS
Straub Technologies

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
steelcomp is offline  
post #13 of 85 (permalink) Old Dec 2nd, 19, 9:10 AM
Senior Tech Team
Scott Foxwell
 
Join Date: Dec 2008
Location: N/E Tennessee
Posts: 3,811
Re: Wider lsa for performance vs tight

Quote:
Originally Posted by Calculated Risk View Post




So:


At 50 number meaningless, check
lsa meaningless, check


Productive day here on Team Chevelle.
You got it.

FOXWELL MOTORSPORTS
Straub Technologies

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
steelcomp is offline  
post #14 of 85 (permalink) Old Dec 2nd, 19, 10:28 AM
Lifetime Premium Member
 
Join Date: Oct 2005
Location: CT,USA
Posts: 12,775
Re: Wider lsa for performance vs tight

Guys, tell me if this makes sense: the LSA number tells us how far away the peak or the "nose" of the intake cam lobe is from the peak/nose/apex of the exhuast lobe, (expressed in crankshaft degrees if I remember this correctly). But it's only going to be a determination of the valve over lap if both lobes are symmetrical, rather than being asymetrical, where you have the opening ramp of each lobe shaped differently than the closing ramp is. And then you have such cam lobe shapes such as the "inverted radius" lobes. So with lobes which aren't symetrical in the shape, the LSA alone cannot be used as a tell-all about what the cam in question will do for your engine power delivery.

And even with cam lobes which are symetrical, (both on the intake and exhaust lobes that is, since some cams might have one of the two symmetrical and the other asymmetrical) although it can tell you the valve overlap in degrees, where that overlap occurs in relation to the piston position, (meaning where the piston is in the bore, and how close it is to TDC) is something that the LSA will NEVER tell you. And exactly where the over lap occurs is definitely something that can, (and usually DOES) effect how your engine behaves.

I think that the only way that LSA can be used, (as a guesstimation at best) would be if you're comparing two cams both having exhaust and intake lobes which are conventional and symmetrical, both cams being from the same manufacture, both being off the shelf pieces, and both being in the same cam "family", ( example would be Comp Cams "Magnum" cams).

So I fully understand Scott Foxwell's points. IDK if I would go as far as to say that LSA tells you nothing, but there definitely IS many other variables which come into play, (such as the ones I've made mention of here above^...and perhaps some variables that I don't even know about). The late Harold Brookshire, (aka "UDHarold") was great at explaining this stuff. I miss that guy tremendously.
steelcomp likes this.

70 Chevelle SS clone (632 CI powered).
BillyGman is offline  
post #15 of 85 (permalink) Old Dec 2nd, 19, 11:35 AM
Senior Tech Team
Scott Foxwell
 
Join Date: Dec 2008
Location: N/E Tennessee
Posts: 3,811
Re: Wider lsa for performance vs tight

Quote:
Originally Posted by BillyGman View Post
Guys, tell me if this makes sense: the LSA number tells us how far away the peak or the "nose" of the intake cam lobe is from the peak/nose/apex of the exhuast lobe, (expressed in crankshaft degrees if I remember this correctly). But it's only going to be a determination of the valve over lap if both lobes are symmetrical, rather than being asymetrical, where you have the opening ramp of each lobe shaped differently than the closing ramp is. And then you have such cam lobe shapes such as the "inverted radius" lobes. So with lobes which aren't symetrical in the shape, the LSA alone cannot be used as a tell-all about what the cam in question will do for your engine power delivery.

And even with cam lobes which are symetrical, (both on the intake and exhaust lobes that is, since some cams might have one of the two symmetrical and the other asymmetrical) although it can tell you the valve overlap in degrees, where that overlap occurs in relation to the piston position, (meaning where the piston is in the bore, and how close it is to TDC) is something that the LSA will NEVER tell you. And exactly where the over lap occurs is definitely something that can, (and usually DOES) effect how your engine behaves.

I think that the only way that LSA can be used, (as a guesstimation at best) would be if you're comparing two cams both having exhaust and intake lobes which are conventional and symmetrical, both cams being from the same manufacture, both being off the shelf pieces, and both being in the same cam "family", ( example would be Comp Cams "Magnum" cams).

So I fully understand Scott Foxwell's points. IDK if I would go as far as to say that LSA tells you nothing, but there definitely IS many other variables which come into play, (such as the ones I've made mention of here above^...and perhaps some variables that I don't even know about). The late Harold Brookshire, (aka "UDHarold") was great at explaining this stuff. I miss that guy tremendously.
You're spot on. Like I said... you can have lots of lobes with the same LSA that have completely different overlap and opening and closing events. You can change the LSA and not change the overlap or you can change the overlap and not change the LSA. I can't tell you how many cams Chris has done where most "experts" (I use the term loosely) would tell you needed 112, 114, etc. for a certain amount of vacuum or overlap or what have you, that ended up being on something like a 108 that completely defied their "understanding". We constantly hear, "Oh, that'll never work", only to hear later, "well I'll be darned"...
If you have two identical cams and the ONLY thing you change is the lobe sep, then I guess you can refer to the LSA as something "significant" and make some assertions as to what the change might do to the performance but a more accurate description of the change would be to describe the overlap or even better yet, how the valve events changed in regards to the piston @ TDC. I'm just trying to get those who are interested to look a little deeper and gain a little more knowledge rather than just regurgitating stuff with no understanding as to actually what's taking place.
BillyGman and 123pugsy like this.

FOXWELL MOTORSPORTS
Straub Technologies

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
steelcomp is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome