Cam Specs

["Bill Thebert" <bthebert@domain.elided>]

A couple of months ago we got the idea to do a complete issue of the
Bulletin on "camshafts".  Stock specs, aftermarket specs, design &
selection criteria, installation how-to, etc.

I was very disappointed with how very *little* information about the cam
profiles I was able to get from the various manufacturers.

Getting a "lift height" figure was pretty easy. If I was lucky I could get
a "duration" figure, or how long the cam maintained a valve as "open" (that
is, open more than some unspecified amount of lift -- either .005" or
050"). A "lobe center" figure could be had most of the time as well.

What I could *not* get most of the time was information re: where in the
pistion stroke the claimed "open duration" BEGAN (e.g., "n-degrees BTDC",
etc.).

What I *really wanted* but was *never* able to get was a true PROFILE --
that is, MULTIPLE data points (lift vs. degrees of cam rotation), so that I
could "see the shape" of the curve.  I wanted to learn whether the curve
was symmetrical, for example.  Does the cam open the valves slowly, and
then slam them shut rapidly?  Or vice versa?

I literally hoped to GRAPH out the curves of the cams -- the stock cam
graph on a paper page of the Bulletin, and a selection of aftermarket
choices printed on acetate perhaps.  So as to be able to "overlay" and
compare easily.  

I was unable to get a true PROFILE from even a single cam manufacturer.
<sigh>  John Landry's experience with Federal Mogul does not surprise me.

Seems they just want us all to be sheep.  

Bill Thebert