Rule of Thumb Accuracy

General engine tech -- Drag Racing to Circle Track

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SchmidtMotorWorks
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Re: Rule of Thumb Accuracy

Post by SchmidtMotorWorks »

GARY C wrote: Sun Jul 08, 2018 11:03 pm They didn't evolve to a wide LSA, more cam grinders spec cams much closer to what DV has been recommending for 20 years not the other way around.
When the 383 first became popular in the early 90's cam company's and tech writers claimed a bigger inch engine needed a wider LSA while DV was proving them wrong by actually testing it.
Back then a tight LSA cam was only considered for dirt track.
You should take this brilliant insight to your favorite cam company and make deal where you develop a market for them and if you succeed, then you get a commission.
I hope it works out for you.
:)
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Re: Rule of Thumb Accuracy

Post by digger »

SchmidtMotorWorks wrote: Sun Jul 08, 2018 9:57 pm
GARY C wrote: Sun Jul 08, 2018 9:33 pm
SchmidtMotorWorks wrote: Sun Jul 08, 2018 8:49 pm

What was this about?
I don't agree to 2 boundary conditions.

Do you realize that your using the results of a tech article where the writer threw 3 cams at an engine with no real comprehensive testing so that you can debunk a tech writer that has written in great detail for decades how the cam effects all of the areas you raise concern about?
Just answering a request.

Decades or centuries; when you use 2 parameters to spec any major performance parameter of a cam, you lose all credibility with me.
In fairness to DV he has mentioned all the caveats, most would agree this should been stated at the start rather than claiming it's the best thing since sliced bread which is how it was marketed ( atleast from my perception).

I found a description on another forum of the test method and mules I'll have to dig it out.

DV has been honest enough to say that he doesn't use 128 himself as it's not comprehensive enough so you aren't really achieving anything by stating this.
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Re: Rule of Thumb Accuracy

Post by paulzig »

gruntguru wrote: Sun Jul 08, 2018 11:10 pm
If the result was better you will have found one of the exceptions to the 128 rule. (DV claims - "For what it does the 128 formula (and the 127 for SBF and the 132 for BBC produces a more accurate LCA prediction than about 99% of cams sold nationwide.")
Then it shows you that the valve events on the 110 cam were fit for purpose, and I for one would want to investigate further and work out why.

To me it would indicate that the valve events were more important than the 110LSA it was ground on.. You could get most of the valve events and overlap to be close to a 108 cam by juggling some number around.
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Re: Rule of Thumb Accuracy

Post by pastry_chef »

A 100% given some opinions are not going to change, consider when it is time to stop engaging those.
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Re: Rule of Thumb Accuracy

Post by GARY C »

SchmidtMotorWorks wrote: Sun Jul 08, 2018 11:15 pm
GARY C wrote: Sun Jul 08, 2018 11:03 pm They didn't evolve to a wide LSA, more cam grinders spec cams much closer to what DV has been recommending for 20 years not the other way around.
When the 383 first became popular in the early 90's cam company's and tech writers claimed a bigger inch engine needed a wider LSA while DV was proving them wrong by actually testing it.
Back then a tight LSA cam was only considered for dirt track.
You should take this brilliant insight to your favorite cam company and make deal where you develop a market for them and if you succeed, then you get a commission.
I hope it works out for you.
:)
Because they will use your info for publication and sales and then talk the customer out of the custom grind in favor of a shelf grind so they don't have to pay the commission... I know that first hand.
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Re: Rule of Thumb Accuracy

Post by GARY C »

paulzig wrote: Sun Jul 08, 2018 10:59 pm
statsystems wrote: Sun Jul 08, 2018 9:09 pm Because I know from decades of doing this shit, that 110 is NOT a good LSA for MOST OE cylinder head architecture.
What if you found an engine that fits the criteria for 128 and instead of 108 its on 110 and shows an excellent result equal to or better than a cam specced by the 128 rule would produce?
How much difference was the average power and how many cams did you run? If you could only choose 1 cam would you have really been that far off with the 108 that 128 specked?
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Re: Rule of Thumb Accuracy

Post by BigBro74 »

paulzig wrote: Sun Jul 08, 2018 10:59 pm
statsystems wrote: Sun Jul 08, 2018 9:09 pm Because I know from decades of doing this shit, that 110 is NOT a good LSA for MOST OE cylinder head architecture.
What if you found an engine that fits the criteria for 128 and instead of 108 its on 110 and shows an excellent result equal to or better than a cam specced by the 128 rule would produce?
If it has the same heads and rockers and compression you probably found a smaller displacement engine (327 instead of 350)
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Re: Rule of Thumb Accuracy

Post by SchmidtMotorWorks »

GARY C wrote: Sun Jul 08, 2018 11:25 pm
Because they will use your info for publication and sales and then talk the customer out of the custom grind in favor of a shelf grind so they don't have to pay the commission... I know that first hand.
[/quote]

That is a very basic marketing problem.
Make your 128 cams the default rather than custom option.
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Re: Rule of Thumb Accuracy

Post by statsystems »

paulzig wrote: Sun Jul 08, 2018 10:59 pm
statsystems wrote: Sun Jul 08, 2018 9:09 pm Because I know from decades of doing this shit, that 110 is NOT a good LSA for MOST OE cylinder head architecture.
What if you found an engine that fits the criteria for 128 and instead of 108 its on 110 and shows an excellent result equal to or better than a cam specced by the 128 rule would produce?

I haven't seen it yet. I spent a better part of the 1990's changing cams for guys who got jacked up with "new" grinds that blow the LSA out and the add a bunch of exhaust duration so the pig will RPM. And you give up the most in the sweet spot. Every. Single. Time.

In fact, I can tell by just driving a car, especially a stick and tell you a damn close guess at the LSA by how weak it is in the middle.
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Re: Rule of Thumb Accuracy

Post by statsystems »

SchmidtMotorWorks wrote: Sun Jul 08, 2018 11:47 pm
GARY C wrote: Sun Jul 08, 2018 11:25 pm
Because they will use your info for publication and sales and then talk the customer out of the custom grind in favor of a shelf grind so they don't have to pay the commission... I know that first hand.
That is a very basic marketing problem.
Make your 128 cams the default rather than custom option.
Go change the world! :)
[/quote]


Let that's just it. There is NO de facto LSA. And it damn sure isn't 110 like Comp has used to kill performance through advertising. It's stupid.
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Re: Rule of Thumb Accuracy

Post by SchmidtMotorWorks »

statsystems wrote: Sun Jul 08, 2018 11:51 pm
SchmidtMotorWorks wrote: Sun Jul 08, 2018 11:47 pm
GARY C wrote: Sun Jul 08, 2018 11:25 pm
Because they will use your info for publication and sales and then talk the customer out of the custom grind in favor of a shelf grind so they don't have to pay the commission... I know that first hand.
That is a very basic marketing problem.
Make your 128 cams the default rather than custom option.
Go change the world! :)

Let that's just it. There is NO de facto LSA. And it damn sure isn't 110 like Comp has used to kill performance through advertising. It's stupid.
[/quote]

You don't seem to understand marketing.
Sorry, but that is too big of a subject to tackle here.
Besides, I have a few more CFD simulations to run tonight.
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Re: Rule of Thumb Accuracy

Post by MadBill »

SchmidtMotorWorks wrote: Sun Jul 08, 2018 11:54 pm..Let that's just it. There is NO de facto LSA. And it damn sure isn't 110 like Comp has used to kill performance through advertising. It's stupid.
The cynic's postulate is that Comp and others go wide on the LSA to save customers from themselves, as they indulge in a lemming-like rush to the bottom of the page for the cam they think they need. #-o
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Re: Rule of Thumb Accuracy

Post by SchmidtMotorWorks »

MadBill wrote: Mon Jul 09, 2018 12:11 am
SchmidtMotorWorks wrote: Sun Jul 08, 2018 11:54 pm..Let that's just it. There is NO de facto LSA. And it damn sure isn't 110 like Comp has used to kill performance through advertising. It's stupid.
The cynic's postulate is that Comp and others go wide on the LSA to save customers from themselves, as they indulge in a lemming-like rush to the bottom of the page for the cam they think they need. #-o
Exactly.

But what would a cam company know about marketing their products?
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Re: Rule of Thumb Accuracy

Post by GARY C »

I think the main thing being missed here is that this was not meant to be the one and only best cam for the engine but a way to get the best cam you can if you are only buying one, installing it and running it!

This is the opening to one of his cam articles from 12 years ago...
The most meaningful statement you can make about power production is that it all starts with cylinder heads that can flow large quantities of air. But having the greatest flowing heads counts for zero if the valves are not opened sufficiently or at the right time in relation to the crankshaft’s rotation, and that very important function falls to the camshaft.

The problem is, if you are something of a novice at this engine business, just about everything to do with cams and valvetrains looks complex, and the truth is, it’s that and more. If cam and valvetrain design at the top level is in your future, you had better thinkin terms of a Ph.D. in mechanical engineering. OK, so most of you are not looking to do that, but would like to understand cams and valvetrains sufficiently to make truly informed power-generating decisions.
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Re: Rule of Thumb Accuracy

Post by statsystems »

SchmidtMotorWorks wrote: Sun Jul 08, 2018 11:59 pm
statsystems wrote: Sun Jul 08, 2018 11:55 pm Bet your ass I have more real world experience with marketing than you have. You aren't as smart as you think you are.
Of course, your vocabulary makes that obvious.


Yup. Had to bring my vocabulary to your level.

I know what the cam companies know about their products. I also know they want to sell what they have that makes the highest profit margin.


In your hippie world that just doesn't happen.
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