chaos.lrk.ar.us!dave.williams (Dave Williams)
hotrod  22 Oct 1993

-> I have access to some very neat engine simulation/tuning software.
-> The software wants complete cam profile data - tappet lift for every
-> degree of crankshaft rotation.  The problem?  The camshaft companies
-> I have spoken with refuse to release complete cam profile data.  They
-> will only give you tiny bits of information.  Close, but not close
-> enough.

That's because most of the cam companies don't *have* any information
to give you.  An average company has a dozen-odd different profiles they
grind on various lobe centers.  Some companies merely use Cam Doctor and
copy other companies' profiles.  Plus, the relationship between the
master lobe and the finished cam depends on several things, including
the size of the wheel used to grind the cam.  Diameter difference
between a new and old wheel can generate a noticeably different profile
on the finished cam.

For your program, you can take the given lift and duration specs and
figure up a simple harmonic profile (any good engineering or shop text).
This should be more than adequate for software purposes.

For a given lifter size or roller size, you're quite limited as to what
you can do.  Most cam grinders are up against the wall on tappet
acceleration anyway, so differences between profiles tend not to be that
great for larger cams.  For small RV-type cams the major factor is cam
and lifter wear.  Sig Erson makes some RV-style lobes that really whack
the valve - harder than their racing profiles, even.


-> I gave Comp Cams a call and they said _No Way_.  They said it would
-> be like giving away the combination to the vault - they'd be handing

Comp doesn't design all their cams.  Some of the profiles were done by
people no longer with the company, others were done by other cam
companies under contract.  The Memphis cam grinders are an inbred bunch,
and the links between the old Cam Dynamics, Comp Cams, Ultradyne, Lazer,
Lunati, and Hypertech go 'way back.

There are no miracles to be found in the cam industry.  Hell, I'm
grateful just to get duration @.050 and lobe centers - too many grinders
give only "advertised" duration and lift.  "Advertised" duration seems
to be based mainly on how lopey the idle is; its meaningless for
building engines.