128 my take, anybody see it like this ?

[F-BIRD'88]

This obsession with wider LSA on US made factory engines is not worldwide. The LSA of the production cams in the humble Morris Mini were on 107.5. Factory performance cams were on 102.5.

What is the intake valve size and engine CID per cylinder on that engine?

[skinny z]

128 is to define the lobe separation angle. If we follow the originator of the 128 rule and continue on to the same author's TM program, you'll find that 4 degrees tends to be built into the cam specs.
What did 128 determine for an LSA with a 1.72" valve, your CID and CR?

This is all I've seen of 128.

128.jpg

LCA = LSA.
As in Lobe Centreline Angle is also described as Lobe Seperation Angle.
Not sure if that was a point of confusion here but it often is elsewhere.

[skinny z]

I thought 128 was for LCA, which I assumed would be for intake,

See above regarding LCA and LSA definitions.

[hoffman900]

128 is to define the lobe separation angle. If we follow the originator of the 128 rule and continue on to the same author's TM program, you'll find that 4 degrees tends to be built into the cam specs.
What did 128 determine for an LSA with a 1.72" valve, your CID and CR?

This is all I've seen of 128.

128.jpg

LCA = LSA.
As in Lobe Centreline Angle is also described as Lobe Seperation Angle.
Not sure if that was a point of confusion here but it often is elsewhere.

LSA is just the average angle of the intake centerline and exhaust centerline. You could have the same LSA with many different centerline angles

[skinny z]

This is all I've seen of 128.

128.jpg

LCA = LSA.
As in Lobe Centreline Angle is also described as Lobe Seperation Angle.
Not sure if that was a point of confusion here but it often is elsewhere.

LSA is just the average angle of the intake centerline and exhaust centerline. You could have the same LSA with many different centerline angles

I'm not entirely certain although I believe the 128 application is for a symmetrical lobe. In that case, there's a clearly defined centerline isn't there? And the math is much simpler.

[hoffman900]

LCA = LSA.
As in Lobe Centreline Angle is also described as Lobe Seperation Angle.
Not sure if that was a point of confusion here but it often is elsewhere.

LSA is just the average angle of the intake centerline and exhaust centerline. You could have the same LSA with many different centerline angles

I'm not entirely certain although I believe the 128 application is for a symmetrical lobe. In that case, there's a clearly defined centerline isn't there? And the math is much simpler.

It is, but I’m not sure why “LCA” is used other than different marketing terminology. LSA is just an average of two centerlines, it doesn’t tell you anything.

[Tom68]

LCA = LSA.
As in Lobe Centreline Angle is also described as Lobe Seperation Angle.
Not sure if that was a point of confusion here but it often is elsewhere.

LCA equals installed position, LSA ground into cam.

LSA Lobe separation angle between intake and exhaust centerlines, install wherever you like.

LCA Lobe centreline angle, one for exhaust, one for intake, defined when you degreed the cam in, add the two and halve them equals LSA.

That's the way I work with it anyways.

If the formula is for LSA, it does it without any exhaust information.

[skinny z]

LSA is just the average angle of the intake centerline and exhaust centerline. You could have the same LSA with many different centerline angles

I'm not entirely certain although I believe the 128 application is for a symmetrical lobe. In that case, there's a clearly defined centerline isn't there? And the math is much simpler.

It is, but I’m not sure why “LCA” is used other than different marketing terminology. LSA is just an average of two centerlines, it doesn’t tell you anything.

So, when going through a catalogue and coming across this...

Screenshot_20220921-071910~2.png

...it doesn't mean anything?

[skinny z]

If the formula is for LSA, it does it without any exhaust information.

That's right.
It takes into account a few basic parameters to establish the spread between centrelines. This is as ground into the cam.
Where you install the intake centerline is entirely up to the individual.

[hoffman900]

I'm not entirely certain although I believe the 128 application is for a symmetrical lobe. In that case, there's a clearly defined centerline isn't there? And the math is much simpler.

It is, but I’m not sure why “LCA” is used other than different marketing terminology. LSA is just an average of two centerlines, it doesn’t tell you anything.

So, when going through a catalogue and coming across this...


Screenshot_20220921-071910~2.png


...it doesn't mean anything?

Nope. That could be;

100ICL and 114ECL
105ICL and 109ECL
107ICL and 107ECL
109ICL and 105ECL
Etc

All would run completely different.


Guys, we’ve been through this a million times here and many have of you have been around long enough to see this discussed many of those times.

[skinny z]

It is, but I’m not sure why “LCA” is used other than different marketing terminology. LSA is just an average of two centerlines, it doesn’t tell you anything.

So, when going through a catalogue and coming across this...


Screenshot_20220921-071910~2.png


...it doesn't mean anything?

Nope. That could be;

100ICL and 114ECL
105ICL and 109ECL
107ICL and 107ECL
109ICL and 105ECL
Etc

All would run completely different.


Guys, we’ve been through this a million times here and many have of you have been around long enough to see this discussed many of those times.

Yes. But now you've thrown duration into the mix.

I'm talking, as the 128 formula describes, how much spread there should be. The duration is another spec altogether.
The 128 formula does not provide a spec and this discussion, as per the title of the thread, is about 128. Nothing else.
It only serves as as a guide for what in this case is a finite application and that has proven empirically to be effective.
It would be up to the user to take this LSA and then also determine what duration, centrelines, lift, et al will provide the results sought after.
Make of it what you will.

[F-BIRD'88]

This obsession with wider LSA on US made factory engines is not worldwide. The LSA of the production cams in the humble Morris Mini were on 107.5. Factory performance cams were on 102.5.

The OEM factory stock 2bbl base 265-283 sbc engines the stock hyd cam had 107° LSA. 172/172 .333" .333"

70's era. 366/427 hd truck camshaft. 103.5 LSA

80's era 267/305 cam 109 LSA

[hoffman900]

So, when going through a catalogue and coming across this...


Screenshot_20220921-071910~2.png


...it doesn't mean anything?

Nope. That could be;

100ICL and 114ECL
105ICL and 109ECL
107ICL and 107ECL
109ICL and 105ECL
Etc

All would run completely different.


Guys, we’ve been through this a million times here and many have of you have been around long enough to see this discussed many of those times.

Yes. But now you've thrown duration into the mix.

I'm talking, as the 128 formula describes, how much spread there should be. The duration is another spec altogether.
The 128 formula does not provide a spec and this discussion, as per the title of the thread, is about 128. Nothing else.
It only serves as as a guide for what in this case is a finite application has proven empirically to be effective.
It would be up to the user to take this LSA and then also determine what duration, centrelines, lift, et al will provide the results sought after.
Make of it what you will.

I’m making of it exactly what it is. A rule of thumb for car show and street rodders, with 350ish ci inline valve 2 valvers and nothing more.

[hoffman900]

This obsession with wider LSA on US made factory engines is not worldwide. The LSA of the production cams in the humble Morris Mini were on 107.5. Factory performance cams were on 102.5.

They also had terrible cylinder heads. ICL 98-102 is typical on old British stuff. On one we built, for racing, we like around 104ICL and around 104-106ECL.

I know of an A-Series that is making 126hp/L naturally aspirated on gasoline with around a 105-107ICL.

Horses for courses.

[skinny z]

Nope. That could be;

100ICL and 114ECL
105ICL and 109ECL
107ICL and 107ECL
109ICL and 105ECL
Etc

All would run completely different.


Guys, we’ve been through this a million times here and many have of you have been around long enough to see this discussed many of those times.

Yes. But now you've thrown duration into the mix.

I'm talking, as the 128 formula describes, how much spread there should be. The duration is another spec altogether.
The 128 formula does not provide a spec and this discussion, as per the title of the thread, is about 128. Nothing else.
It only serves as as a guide for what in this case is a finite application has proven empirically to be effective.
It would be up to the user to take this LSA and then also determine what duration, centrelines, lift, et al will provide the results sought after.
Make of it what you will.

I’m making of it exactly what it is. A rule of thumb for car show and street rodders, with 350ish ci inline valve 2 valvers and nothing more.

Precisely.