Don Terrill’s Speed-Talk

skinny z wrote: ↑Wed Sep 21, 2022 9:49 am

hoffman900 wrote: ↑Wed Sep 21, 2022 9:46 am

skinny z wrote: ↑Wed Sep 21, 2022 9:40 am

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.

skinny z wrote: ↑Wed Sep 21, 2022 9:40 am

hoffman900 wrote: ↑Wed Sep 21, 2022 9:28 am

skinny z wrote: ↑Wed Sep 21, 2022 9:23 am

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.

Stan Weiss wrote: ↑Wed Sep 21, 2022 10:08 am 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 wrote: ↑Wed Sep 21, 2022 10:33 am 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.

hoffman900 wrote: ↑Wed Sep 21, 2022 9:51 am

skinny z wrote: ↑Wed Sep 21, 2022 9:49 am

hoffman900 wrote: ↑Wed Sep 21, 2022 9:46 am

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.

F-BIRD'88 wrote: ↑Wed Sep 21, 2022 10:33 am

skinny z wrote: ↑Wed Sep 21, 2022 9:40 am

hoffman900 wrote: ↑Wed Sep 21, 2022 9:28 am

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.

Orr89rocz wrote: ↑Wed Sep 21, 2022 2:17 pm

F-BIRD'88 wrote: ↑Wed Sep 21, 2022 10:33 am

skinny z wrote: ↑Wed Sep 21, 2022 9:40 am

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

UDHarold wrote: ↑Tue Apr 28, 2009 11:31 am 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

Orr89rocz wrote: ↑Wed Sep 21, 2022 2:17 pm

F-BIRD'88 wrote: ↑Wed Sep 21, 2022 10:33 am

skinny z wrote: ↑Wed Sep 21, 2022 9:40 am

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 wrote: ↑Wed Sep 21, 2022 2:43 pm 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.

juuhanaa wrote: ↑Wed Sep 21, 2022 2:53 pm hmmmm


307 601.png

skinny z wrote: ↑Wed Sep 21, 2022 2:50 pm

hoffman900 wrote: ↑Wed Sep 21, 2022 2:43 pm 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?

Orr89rocz wrote: ↑Wed Sep 21, 2022 2:17 pm

F-BIRD'88 wrote: ↑Wed Sep 21, 2022 10:33 am

skinny z wrote: ↑Wed Sep 21, 2022 9:40 am

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