Giving a talk on cam selection, and need your input

General engine tech -- Drag Racing to Circle Track

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Re: Giving a talk on cam selection, and need your input

Post by SchmidtMotorWorks » Thu Aug 09, 2018 11:51 pm

Maybe the limits of hydraulic roller lifters.
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Re: Giving a talk on cam selection, and need your input

Post by GARY C » Thu Aug 09, 2018 11:53 pm

MadBill wrote:
Thu Aug 09, 2018 11:45 pm
GARY C wrote:
Thu Aug 09, 2018 4:45 pm
...Ask your audience what they would like to know... a Q&A, that way your not spending time covering what they already know....
How much lead time do you have? Asking the attendees this in advance would be a plus.

PS: My question(s) would be 'On a new-to-you* pushrod application (*valve gear geometry, component weights, etc.), what factors govern/how do you come up with the correct seat and open spring loads for your lobes and does the tolerance of roller cams for higher loads mean that you typically dial in more 'insurance' with them?
He may have limited time, maybe a simple case of passing around a few post-it note pads while everyone is getting ready and then addressing some of the questions as opposed to trying to do it person by person.

Good question by the way.
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Re: Giving a talk on cam selection, and need your input

Post by Atom » Fri Aug 10, 2018 2:48 am

Is this going to be recorded or is this going to be only for attendees?
I'm sure lots of people here would love to watch your talk, including me.

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Re: Giving a talk on cam selection, and need your input

Post by shiftbyear » Fri Aug 10, 2018 5:13 am

How about improved dyno results that don't translate to a faster car at the track?

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Re: Giving a talk on cam selection, and need your input

Post by Warp Speed » Fri Aug 10, 2018 6:59 am

CamKing wrote:
Thu Aug 09, 2018 2:03 pm
I'll be giving a talk on cam selection, and need some help.
What questions need to be covered?
What common mistakes do people make?
What would you like to learn about cam selection?
What day are you doing this?

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Re: Giving a talk on cam selection, and need your input

Post by Alan Roehrich » Fri Aug 10, 2018 7:11 am

Briefly name and explain acceleration terms, what they mean, and how they're used to select a lobe profile/family. This should be really brief. Possibly touch on what they mean for flow at the valve.

More in depth maybe, how you determine duration, ICL, and LSA, as well as opening and closing events, for a given application, and why. How each affects peak HP and peak torque, and where they happen, as well as what they do to area under the curve.

Explain ideal cam lift vs. what the head flows on the flow bench.

Also, how to test a cam on the dyno, in order to give you data that you need to make changes or improvement. And the same for track testing. What information can they collect and share.

The things an engine builder wants to know are "how do I help my cam guy get me the best possible cam the first time?", "how do I help him to give me the cams that achieve my goals?"

Someone mentioned header design up thread. So, how can an engine builder make a header change that can let you make a cam change to make them faster? For example, in a given combination, could we change the collector design, or even change between a 4 into 1 and a 4-2-1, and be able to change the cam to achieve a goal? Could I make a header change that would let me run a smaller duration lobe on the exhaust, and then run a bigger intake lobe, with the same ICL/LSA and the same overlap?

Think about this from your position. Tell them how not to make mistakes you've seen engine builders make. Think about times you dealt with engine builders, or saw others in your position do the same, and thought "I wish this guy knew _____ or understood _____".

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Re: Giving a talk on cam selection, and need your input

Post by tenxal » Fri Aug 10, 2018 7:55 am

I would echo Alan's comments, particularly the header/cam relationship.

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Re: Giving a talk on cam selection, and need your input

Post by MadBill » Fri Aug 10, 2018 9:20 am

Her's one that's come up a number of times: In assessing how well a cam's specs align with your engine's needs, is a 'well specced' cam more or less sensitive to indexing than one that misses the mark?
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Re: Giving a talk on cam selection, and need your input

Post by CamKing » Fri Aug 10, 2018 10:02 am

Warp Speed wrote:
Fri Aug 10, 2018 6:59 am
CamKing wrote:
Thu Aug 09, 2018 2:03 pm
I'll be giving a talk on cam selection, and need some help.
What questions need to be covered?
What common mistakes do people make?
What would you like to learn about cam selection?
What day are you doing this?
Not sure yet.
You planning on sitting in the back of the room, and shooting spit balls at me ? :lol:
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Re: Giving a talk on cam selection, and need your input

Post by CamKing » Fri Aug 10, 2018 10:03 am

Atom wrote:
Fri Aug 10, 2018 2:48 am
Is this going to be recorded or is this going to be only for attendees?
I have no idea.
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Re: Giving a talk on cam selection, and need your input

Post by RDY4WAR » Fri Aug 10, 2018 10:26 am

How to calculate the valve spring force needed for a specific cam.
Common mistake: Assuming LSA is the most important spec for a camshaft.

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Re: Giving a talk on cam selection, and need your input

Post by CamKing » Fri Aug 10, 2018 11:25 am

I'm thinking, maybe I spend a few minutes going over how I select a cam for a customer, then a few minutes addressing the common mistakes I see people make, then answer questions.
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Re: Giving a talk on cam selection, and need your input

Post by Stan Weiss » Fri Aug 10, 2018 11:38 am

Since most people here are using cam in block. How about the relationship between cam lobe and rocker arm ratio for correct valve lift curve.

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Re: Giving a talk on cam selection, and need your input

Post by andyf » Fri Aug 10, 2018 11:51 am

If I was going to give a talk on that subject I'd probably use a flow chart to show the process. For example, if a guy calls me up and says he needs a cam for his engine the first thing I'd ask him if it is a race car or a street car. If it is a race car then you ask if it is a weekend bracket car or a pro car. A weekend car doesn't need the last bit of power so you go with a lobe that is parts friendly. If it is a race car you have to know if it is a drag race car or a circle track or pulling truck or whatever.

The flow chart is one approach but it could be easier to just focus on the power band required. Where does the engine need to make power and how long does it need to last? Marine racing is different than drag racing which is different than land speed or circle track or road racing, etc.

I suppose a person could dive way into the details on one particular engine but the answers might get kind of murky. At the end of the day hardly anyone ever really knows why one particular lobe worked better than another. It is usually some sort of interaction between valve train harmonics and/or intake wave tuning but even the most sophisticated race teams sometimes just shrug their shoulders and say "guess she likes this one".
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Re: Giving a talk on cam selection, and need your input

Post by CamKing » Fri Aug 10, 2018 12:08 pm

andyf wrote:
Fri Aug 10, 2018 11:51 am
but even the most sophisticated race teams sometimes just shrug their shoulders and say "guess she likes this one".
No winning "sophisticated race team" says that.
Those days are long gone.
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