LSA and LCA ??

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Turbo231
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LSA and LCA ??

Post by Turbo231 » Wed Jul 11, 2018 4:45 pm

Just got through the post started by David Vizard on Rule of Thumb. All I can say as a newbie is, you guys can be pretty passionate about your opinions. Of course as a newbie, there is no way in heck I am getting into one of these discussions. At least for now :) .

I do have a question though: I saw LSA and LCA and they seemed to be used interchangeably. From my understanding, LSA is "lobe separation angle" and is actual cam degrees (not crankshaft) between intake and exhaust lobes. I have not seen LCA which looks to be "lobe center angle". Are these the same or not? If they are same, what does majority on this site use? Thanks.

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Re: LSA and LCA ??

Post by GARY C » Wed Jul 11, 2018 4:53 pm

Yes they are the same, LSA seems to be more common from what I have seen.
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Re: LSA and LCA ??

Post by steve cowan » Wed Jul 11, 2018 4:58 pm

Turbo,
LSA - LCA same deal
ICL - intake centreline
LCA - lobe centreline angle not sure where that came from maybe England term
yes great forum,alot of information here and some extremely smart people
the only advice i have is stay away from the slinging matches unless you are packing :D
steve c

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Re: LSA and LCA ??

Post by Walter R. Malik » Wed Jul 11, 2018 7:08 pm

Turbo231 wrote:
Wed Jul 11, 2018 4:45 pm
Just got through the post started by David Vizard on Rule of Thumb. All I can say as a newbie is, you guys can be pretty passionate about your opinions. Of course as a newbie, there is no way in heck I am getting into one of these discussions. At least for now :) .

I do have a question though: I saw LSA and LCA and they seemed to be used interchangeably. From my understanding, LSA is "lobe separation angle" and is actual cam degrees (not crankshaft) between intake and exhaust lobes. I have not seen LCA which looks to be "lobe center angle". Are these the same or not? If they are same, what does majority on this site use? Thanks.
Sometimes those terms are incorrectly interchanged:
Lobe Separation Angle is indeed the number of cam degrees between the intake and exhaust lobes.
Lobe Center Angle is the angle in crankshaft degrees of THAT particular lobe in relation to top dead center of the engine for that cylinder being measured.

They are usually NOT the same number but, sometimes are.
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Re: LSA and LCA ??

Post by cjperformance » Wed Jul 11, 2018 7:38 pm

Walter R. Malik wrote:
Wed Jul 11, 2018 7:08 pm
Turbo231 wrote:
Wed Jul 11, 2018 4:45 pm
Just got through the post started by David Vizard on Rule of Thumb. All I can say as a newbie is, you guys can be pretty passionate about your opinions. Of course as a newbie, there is no way in heck I am getting into one of these discussions. At least for now :) .

I do have a question though: I saw LSA and LCA and they seemed to be used interchangeably. From my understanding, LSA is "lobe separation angle" and is actual cam degrees (not crankshaft) between intake and exhaust lobes. I have not seen LCA which looks to be "lobe center angle". Are these the same or not? If they are same, what does majority on this site use? Thanks.
Sometimes those terms are incorrectly interchanged:
Lobe Separation Angle is indeed the number of cam degrees between the intake and exhaust lobes.
Lobe Center Angle is the angle in crankshaft degrees of THAT particular lobe in relation to top dead center of the engine for that cylinder being measured.

They are usually NOT the same number but, sometimes are.
Yes thats how I have seen/used it.
But always double ask/check on another persons or companies terminology so as not to get mixed up!
Craig.

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Re: LSA and LCA ??

Post by hoffman900 » Wed Jul 11, 2018 7:39 pm

The other is LSA is about useless without knowing the centerline of either the intake or exhaust.
-Bob

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Re: LSA and LCA ??

Post by user-23911 » Thu Jul 12, 2018 2:52 am

steve cowan wrote:
Wed Jul 11, 2018 4:58 pm
Turbo,
LSA - LCA same deal
ICL - intake centreline
LCA - lobe centreline angle not sure where that came from maybe England term
yes great forum,alot of information here and some extremely smart people
the only advice i have is stay away from the slinging matches unless you are packing :D

There's 3 numbers. LSA, in cam degrees, ICL and ECL both of which are in crank degrees, the no of crank degrees between TDC and the middle of the lobe.The middle of the lobe usually being half way betwen the open and the close, not peak lift.

If you add the ICL to the ECL then halve it, you get LSA.
So if ICL and ECL are the same, so is LSA.
If ICL and ECL are different, LSA is the average.


ICL and ECL are important on most DOHC engines as it's adjustable.

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Re: LSA and LCA ??

Post by midnightbluS10 » Thu Jul 12, 2018 3:28 am

LSA and LCA aren't the same thing and they aren't interchangeable. Grumpy has a good post that explains most of it. No reason to type it all out when someone else already has.


http://garage.grumpysperformance.com/in ... ngle.3816/

And a link from Cartech Books, as well. Cartech is an extremely popular publisher that publishes known good information.


https://www.cartechbooks.com/techtips/camshafts1/

Like posted in the thread above, LSA, lobe separation angle, is ground into the cam. LCA, lobe centerline angle, can be changed through indexing the cam when degreeing it in. They're not the same thing. Some people may unknowingly use them interchangeably but they aren't the same thing.


DV has a pretty good article about the subject, as well. Be forewarned, it mentions a "rule of thumb" in the article. Not THE rule of thumb. Some of you may want to stay out of there. Smh.


https://www.hotrod.com/articles/cam-lob ... ngle-tech/

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Re: LSA and LCA ??

Post by hoffman900 » Thu Jul 12, 2018 5:33 am

As said before, LSA is just the average of the intake and exhaust center lines.

You could represent the same thing as:

106* LSA camshaft installed 4* advanced (102* intake centerline, 110* exhaust centerline).

Or..

Intake Centerline: 102*
Exhaust Centerline: 110*

Knowing the centerlines tells you exactly what’s happening and is more informative. I believe the few cam designers who have posted here have all said that LSA is just an artifact from the camshaft machining process, and is just a lazy way to represent something.
-Bob

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Re: LSA and LCA ??

Post by steve cowan » Thu Jul 12, 2018 5:43 am

hi guys,
i am more than happy to be corrected but OP is talking about DV and his rule of thumb deal,
i just re-read how to build horsepower pages 103-107 and DV talks of LCA lobe centreline angle and no mention of LSA thats why i mentioned it as i did in my earlier post, i understand what Walter and Craig are saying but i interpreted as per DV as the OP was talking about,if i am incorrect that is fine as i may of been a bit confused myself
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Re: LSA and LCA ??

Post by cjperformance » Thu Jul 12, 2018 9:53 am

steve cowan wrote:
Thu Jul 12, 2018 5:43 am
hi guys,
i am more than happy to be corrected but OP is talking about DV and his rule of thumb deal,
i just re-read how to build horsepower pages 103-107 and DV talks of LCA lobe centreline angle and no mention of LSA thats why i mentioned it as i did in my earlier post, i understand what Walter and Craig are saying but i interpreted as per DV as the OP was talking about,if i am incorrect that is fine as i may of been a bit confused myself
I dont have that book Steve, in what context is LCA used?
Craig.

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Re: LSA and LCA ??

Post by Turbo231 » Thu Jul 12, 2018 10:27 am

midnightbluS10 wrote:
Thu Jul 12, 2018 3:28 am
LSA and LCA aren't the same thing and they aren't interchangeable. Grumpy has a good post that explains most of it. No reason to type it all out when someone else already has.


http://garage.grumpysperformance.com/in ... ngle.3816/

And a link from Cartech Books, as well. Cartech is an extremely popular publisher that publishes known good information.


https://www.cartechbooks.com/techtips/camshafts1/

Like posted in the thread above, LSA, lobe separation angle, is ground into the cam. LCA, lobe centerline angle, can be changed through indexing the cam when degreeing it in. They're not the same thing. Some people may unknowingly use them interchangeably but they aren't the same thing.


DV has a pretty good article about the subject, as well. Be forewarned, it mentions a "rule of thumb" in the article. Not THE rule of thumb. Some of you may want to stay out of there. Smh.


https://www.hotrod.com/articles/cam-lob ... ngle-tech/
I just looked at the Hot Rod article you referenced and it looks like Mr. Vizard is using LCA as what I have always called LSA, the angle between the intake and exhaust lobe centerlines (in cam degrees, this is very important to understand). And my definition of lobe centerline is the midway point between the opening and closing points and does not have to be at max lift. Of course with a symmetrical lobe profile, max lift is on the centerline. To fully understand all these camshaft concepts, the camshaft manufactures and engine builder's should try to get together and publish a standard of nomenclature to be used. I think that would eliminate a lot of the confusion, especially at the consumer level. Maybe Speed Talk could at least create a standard that all board members could use. Might eliminate some bickering :) .

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Re: LSA and LCA ??

Post by MadBill » Thu Jul 12, 2018 1:37 pm

I've been guilty most of my life of using the LCA term by preference, but interchangeably with LSA, to indicate the angle in cam degrees between lobe centerlines, but as per this thread only the latter is correct. However the terms remain interchangeable in popular use to such an extent that no one should assume a difference.
It's like torque measurement: the correct unit is pound-foot, but more often than not foot/pound is incorrectly used.
(and then of course there's "El-de-brock", but let's not go there...) :)
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Re: LSA and LCA ??

Post by GARY C » Thu Jul 12, 2018 1:39 pm

MadBill wrote:
Thu Jul 12, 2018 1:37 pm
I've been guilty most of my life of using the LCA term by preference, but interchangeably with LSA, to indicate the angle in cam degrees between lobe centerlines, but as per this thread only the latter is correct. However the terms remain interchangeable in popular use to such an extent that no one should assume a difference.
It's like torque measurement: the correct unit is pound-foot, but more often than not foot/pound is incorrectly used.
(and then of course there's "El-de-brock", but let's not go there...) :)
You mean the Super Model Kelly? :)
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Re: LSA and LCA ??

Post by BigBro74 » Thu Jul 12, 2018 1:54 pm

MadBill wrote:
Thu Jul 12, 2018 1:37 pm
I've been guilty most of my life of using the LCA term by preference, but interchangeably with LSA, to indicate the angle in cam degrees between lobe centerlines, but as per this thread only the latter is correct. However the terms remain interchangeable in popular use to such an extent that no one should assume a difference.
It's like torque measurement: the correct unit is pound-foot, but more often than not foot/pound is incorrectly used.
(and then of course there's "El-de-brock", but let's not go there...) :)
I am in the same boat here Bill, and at many sources may be somewhat ambiguous.

From Isky glossary of terms (they stayed out of it lol)

"LOBE CENTERS: The distance measured in degrees between the center line of the intake lobe and the center line of the exhaust lobe of the same cylinder."

http://www.iskycams.com/glossary.html

Jason

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