From: Dan Malek <emory!westford.ccur.com!dan>
X-Source: The Hotrod Mailing list
Date: Oct 1993
Subject: Re: Very outdated thinking by cam companies 

My $0.02 + tax.

I have discussed this cam issue with Brian a little bit before.  I
can sympathize with his situation, but you have to consider the
cam company's point of view.  In many racing classes, the cam
profile is one of the few areas of uncontrolled modification.  You
may be told what type of cam to use (hydraulic, flat, roller), but
the profile is up to you to choose.

At the machine shop, we have a computer assisted tool for measuring
cams.  After looking at hundreds of cams, I can say that duration and
lift mean very little.  Two cams with identical duration and lift can
be totally different in profile, and there are hundreds of profiles
to choose from, not including custom grinds.  I am sure a cam company
wants to keep this as close to them as possible.  It is not that you
can't find out, but......

...One cam company we used to deal with gave someone else the profile to
one of our custom ground cams.  Needless to say, we were quite pissed
since it was the result of hundreds of hours of dyno time and thousands
of dollars of custom cam purchases.  We don't do business with them
anymore, and they don't understand why.  The new company we do business
with has been sworn to secrecy, and they actually like working that way.
It is possible that companies (except one) can only enforce this kind of
secrecy if they do it in a very general, company-wide policy.

Some tech notes.  It is surprising (well to me anyway) how much the
cam timing varies from one lobe to another on certain cams.  The cam
companies seem to have the duration/lift nailed down, but the timing
is something to be desired.  I have seen some vary as much as five
degrees across the cam.  Now that companies we deal with know we measure
the cams, the custom stuff we get is quite accurate, so the technology
is there (perhaps the attention to quality needs adjusting).  Also,
any non-custom cam has quite gentle lobe ramps, to protect the valve
train.  If you want more aggressive ramps, you need to be able to talk
valve train acceleration and forces.  It seems the cam companies have
some serious tools (simulators and other software possibly) to help
design aggressive ramps within the capabilities of your valve train.
With such cams, they are also very interested in wear and reliability
feedback.


	-- Dan

From: Dan Malek <emory!gatech!westford.ccur.com!dan>
X-Source: The Hotrod Mailing list
Date: Oct 1993
Subject: Re: Very outdated thinking by cam companies 
X-Sequence: 6730

> Date:  Fri, 22 Oct 93 13:33 EDT
> From:  emory!chaos.lrk.ar.us!dave.williams (Dave Williams)
> 
>-> From: Dan
>
>-> lift mean very little.  Two cams with identical duration and lift can
>-> be totally different in profile, and there are hundreds of profiles
>-> to choose from, not including custom grinds.

> Not that much different.  I've done my time with the degree wheel and
>dial indicator, and every grinder is up against the same valve spring
>and lifter diameter limits.

OK...Perhaps I should rephrase that.  They give very different results
in the engine.  We recently rebuilt a Super Modified big block Chevy,
and threw in a new cam that was supposed to be identical to the old one.
The engine was down 75 HP (725 vs. 800 HP).  Couldn't figure it out
until we "doctored" the cam.  Same lift, same duration, different lobe
profile.

>-> ...One cam company we used to deal with gave someone else the profile
>-> to one of our custom ground cams.  Needless to say, we were quite
>-> pissed since it was the result of hundreds of hours of dyno time and
>-> thousands

> So?  Chances are very good your special profile didn't do anything
>great for the other guy unless he was running almost exactly the same
>engine you were.  And even then, different drivers, cars, or tracks can
>require the torque peak moved up or down for the best times.

In this case, it was a competitor engine builder, building a similar
engine for the same racing class where horsepower was everything.

> This was really a custom profile?  Most cam companies consider
>generating a new master cam to be a major operation.  Back when I was
>running Pinto engines, I ran into that.  The Pinto's cam-on-rocker
>layout requires a wildly asymmetric lobe to give a symmetric curve at
>the valve.  The cheapest quote I got for a new master cam was several
>times more money than I had in the entire car.

> Most companies consider developing new masters as a capital
>expenditure, because it takes LOTS of time.  Who paid for the new
>profile?  If you weren't paying in the four figure range per copy, I'd
>say the cam company was eating the costs, so the master belonged to
>them.

All I can do is describe the process.  My assumption was that they are
done on a CNC machine.  We either send them a profile print out from
the engine simulator, or talk to them on the phone and give them twenty
or so data points.  We sometimes discuss valve train forces, and from
the information they provide I made another assumption that they have
some kind of computer assistance.  The cam we get back is exactly what
we ask for, and the price was not unreasonable.  We also do stuff like
change the lobe or lobe timing on some cylinders due to the flow of
the intake manifold.  That does not seem to be a problem for the cam
manufacturer either.

> For most engines, the problem is WEAR.  That's why Detroit finally went
>back to roller cams.  Very strange things happen at the lobe/lifter
>interface - a typical problem is pitting.  Used to, engineers thought it
>was a form of spalling.  Current thinking is that the extreme pressure
>over the cam nose causes the oil to eat the lifter.  That is, unless a
>new theory is extant.  You want a badass profile?  How long does it need
>to last?  Radical profiles don't last long.  Fortunately (for cam
>grinders, anyway) motor longevity goes down at least as fast as cam
>wear goes up.

We are talking race only engines here that have these profiles.  The valve
train in our latest technology engines contains as much titanium and carbon
fiber that is available.  The valve springs go first, and are changed after
practice plus one race.  The next on the list is the roller lifter.  We
beat the needles right out of the roller.  They get checked after every
race and maybe last three.  The cams seem to last quite a while, of course
we swap them out due to profile changes before they usually get a chance
to wear out completely.  The middle of the ramp gets beat up first, the
nose looks OK.  We are running seat pressures around 230 lbs.

I don't know how they make 'em, but we get what we ask for.


	-- Dan