128 my take, anybody see it like this ?

[hoffman900]

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.

I’m not sure what the discussion is though. If that’s you, just copy a recipe out of a book and have at it. Certainly not “speed” talk.

[Stan Weiss]

I don't know why David likes to use LCA and not LSA. Could be for the same reason he spells a number of words differently but correctly (maybe a British thing)

ICL = Installed position.

Remember 128 is just one of a number of formulas needed / used in TMC. I believe at one time David may have posted the formula for how a CR of other than 10.5:1 would change things. I also believe David has it some of his books graphs of how some of this works.

In TMC there is no question where everything is positioned. It calculates / displays
LCA
Intake Duration
Exhaust Duration
Overlap
Cam Advance
ICL

Stan

[F-BIRD'88]

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.

When you read DV's books and select the overlap as per the overlap pie chart for the intended application RPM and build level. and apply the 128 formula for that engine you get a camshaft duration. (within a workable relevent range)
Mostly biased for a single pattern camshaft.

You can then tweek things a bit if you want a dual pattern cam. This tends to widen the LSA a hair. It doesn't have to but...- it tends to-. And then you can tweek the installed position "advance" .. Don't be timid to play with this +/-.
And as DV said in his comments a Dual Plane intake manifold can tolerate a slight widening of the LSA a hair. VS what a single plane manifold is going to favour to make good torque.

It is intended as a guide for the end user to get a high torque per cid street strip perf engine.
A better but simple method VS just selecting from the catalog page.

[skinny z]

I don't know why David likes to use LCA and not LSA. Could be for the same reason he spells a number of words differently but correctly (maybe a British thing)

ICL = Installed position.

Remember 128 is just one of a number of formulas needed / used in TMC. I believe at one time David may have posted the formula for how a CR of other than 10.5:1 would change things. I also believe David has it some of his books graphs of how some of this works.

In TMC there is no question where everything is positioned. It calculates / displays
LCA
Intake Duration
Exhaust Duration
Overlap
Cam Advance
ICL

Stan

Thanks for that Stan.
I couldn't have said it better myself. Not would I expect myself to.

[skinny z]

When you read DV's books and select the overlap as per the overlap pie chart for the intended application RPM and build level. and apply the 128 formula for that engine you get a camshaft duration. (within a workable relevent range)
Mostly biased for a single pattern camshaft.

You can then tweek things a bit if you want a dual pattern cam. This tends to widen the LSA a hair. It doesn't have to but...- it tends to-. And then you can tweek the installed position "advance" .. Don't be timid to play with this +/-.
And as DV said in his comments a Dual Plane intake manifold can tolerate a slight widening of the LSA a hair. VS what a single plane manifold is going to favour to make good torque.

It is intended as a guide for the end user to get a high torque per cid street strip perf engine.
A better but simple method VS just selecting from the catalog page.

Exactly.

[skinny z]

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.

I’m not sure what the discussion is though. If that’s you, just copy a recipe out of a book and have at it. Certainly not “speed” talk.

You'll have to ask the OP about that. I only offered an explanation as I understood it.
As for me, I rely on the experts to spec my cams. That said, I would be remiss if I didn't having a working knowledge of the process.
And that's where "speed" talk comes in.

[Orr89rocz]

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.

When you read DV's books and select the overlap as per the overlap pie chart for the intended application RPM and build level. and apply the 128 formula for that engine you get a camshaft duration. (within a workable relevent range)
Mostly biased for a single pattern camshaft.

You can then tweek things a bit if you want a dual pattern cam. This tends to widen the LSA a hair. It doesn't have to but...- it tends to-. And then you can tweek the installed position "advance" .. Don't be timid to play with this +/-.
And as DV said in his comments a Dual Plane intake manifold can tolerate a slight widening of the LSA a hair. VS what a single plane manifold is going to favour to make good torque.

It is intended as a guide for the end user to get a high torque per cid street strip perf engine.
A better but simple method VS just selecting from the catalog page.

It’s unfortunate the catalog cams never seem to come in under 110 lsa. Can find some under that but much more limited than the 110-114 lsa cams out there. So sucks the program gives you 104-108 lsa stuff and you still have to get it custom ground if there are cores available for that tight lobe separation

[hoffman900]

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.

When you read DV's books and select the overlap as per the overlap pie chart for the intended application RPM and build level. and apply the 128 formula for that engine you get a camshaft duration. (within a workable relevent range)
Mostly biased for a single pattern camshaft.

You can then tweek things a bit if you want a dual pattern cam. This tends to widen the LSA a hair. It doesn't have to but...- it tends to-. And then you can tweek the installed position "advance" .. Don't be timid to play with this +/-.
And as DV said in his comments a Dual Plane intake manifold can tolerate a slight widening of the LSA a hair. VS what a single plane manifold is going to favour to make good torque.

It is intended as a guide for the end user to get a high torque per cid street strip perf engine.
A better but simple method VS just selecting from the catalog page.

It’s unfortunate the catalog cams never seem to come in under 110 lsa. Can find some under that but much more limited than the 110-114 lsa cams out there. So sucks the program gives you 104-108 lsa stuff and you still have to get it custom ground if there are cores available for that tight lobe separation

That’s because catalog cams are designed and sold to be mostly dummy proof / easy to tune / easy to drive around for what constitutes the majority of their sales. Everyone keeps bringing up dyno sheets that start at 3500rpm and I bet for 95% of those catalogue cam buyers they spend 95%+ of their time below that.

A cam with durations around 260* at .050” + and ground 104-106 (straight up) is going to be too much for a lot of those people.

Even someone like Harold Brookshire said as much:

Does anyone have a list of cam companies offering BBC cams on such tight LSAs? Or of BBC cams made with such LSAs?
I know at UltraDyne, from 1980 on, two of our most popular BBC cams, the BB288/296F7 and the BB286/300R7, were extremely popular ground on 107 LSAs.
However, they were almost unstreetable, at least for the average guy.....

UDHarold

[skinny z]

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.

When you read DV's books and select the overlap as per the overlap pie chart for the intended application RPM and build level. and apply the 128 formula for that engine you get a camshaft duration. (within a workable relevent range)
Mostly biased for a single pattern camshaft.

You can then tweek things a bit if you want a dual pattern cam. This tends to widen the LSA a hair. It doesn't have to but...- it tends to-. And then you can tweek the installed position "advance" .. Don't be timid to play with this +/-.
And as DV said in his comments a Dual Plane intake manifold can tolerate a slight widening of the LSA a hair. VS what a single plane manifold is going to favour to make good torque.

It is intended as a guide for the end user to get a high torque per cid street strip perf engine.
A better but simple method VS just selecting from the catalog page.

It’s unfortunate the catalog cams never seem to come in under 110 lsa. Can find some under that but much more limited than the 110-114 lsa cams out there. So sucks the program gives you 104-108 lsa stuff and you still have to get it custom ground if there are cores available for that tight lobe separation

That does seem to be the case. The circle track flat tappet section of the catalogues have a fair offering but hydraulic roller choices are definitely limited.
It was once explained to me (by a famous engine builder no less) that the 110 LSA is there to keep the average guy from "overcamming". Seems catalogue cam selections are often based solely on duration and the bigger the better. The wide split obviously tames the overlap and all the difficulties that can come along with having too much.
At least that's what I was told.

[skinny z]

I see hoffman900 has the same sentiment as the famous engine builder I alluded to above.

[skinny z]

A cam with durations around 260* at .050” + and ground 104-106 (straight up) is going to be too much for a lot of those people.

How about 234 @ .050" on a 108 and a 104 ICL?

[juuhanaa]

hmmmm

307 601.png

[skinny z]

hmmmm


307 601.png

12:1 is outside of the operating parameters of the 128 rule.
LSA will widen according to the 128 rule and on which TM is based.
Do the same specs with 10.5:1 and post up.

[hoffman900]

A cam with durations around 260* at .050” + and ground 104-106 (straight up) is going to be too much for a lot of those people.

How about 234 @ .050" on a 108 and a 104 ICL?

Have no idea. How much lift? And if it’s a bunch, how are you planning on keeping that together.

There are a lot of street set ups out there with aggressive lobes / valve lift profiles that would self destruct pretty quickly if they spent any amount of time at higher rpm’s. Stuff like that is the reason Car Craft would make 450hp with a $4000 build (just had to last long enough to make the pull for the article) but to do the same and make it live for 3000 miles in racing would be a $20k + engine.

[F-BIRD'88]

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.

When you read DV's books and select the overlap as per the overlap pie chart for the intended application RPM and build level. and apply the 128 formula for that engine you get a camshaft duration. (within a workable relevent range)
Mostly biased for a single pattern camshaft.

You can then tweek things a bit if you want a dual pattern cam. This tends to widen the LSA a hair. It doesn't have to but...- it tends to-. And then you can tweek the installed position "advance" .. Don't be timid to play with this +/-.
And as DV said in his comments a Dual Plane intake manifold can tolerate a slight widening of the LSA a hair. VS what a single plane manifold is going to favour to make good torque.

It is intended as a guide for the end user to get a high torque per cid street strip perf engine.
A better but simple method VS just selecting from the catalog page.

It’s unfortunate the catalog cams never seem to come in under 110 lsa. Can find some under that but much more limited than the 110-114 lsa cams out there. So sucks the program gives you 104-108 lsa stuff and you still have to get it custom ground if there are cores available for that tight lobe separation

There are lots of catalog cams that are 104 105 and 106 and 108 LSA.. You just have to look.
Check out the Isky cams stuff. These cams ALWAYS work well.

Check out the Linati / UDHAROLD "Street/Strip" cams series and the tight lash stuff.