"Assuming I do have a stock cam and that its real duration is about 256 degrees, then the duration would have to have been checked/measured somewhere between the 0.010" and 0.015" of lift you mentioned."
I do both event points and centerline, sometimes on more than 1 lobe.
Some grinds are set by setting the crank angle at a specific point in lift. Some just split the overlap. The results should all be the same or very close.
I can't add anything to what is in the Crane article, the applications are different but methods the same. I don't have any online references, all of my stuff is paper!
Take 2 aspirin and post more in the morning!
g.
--Previous Message--
: Thanks for the additional information.
:
: In researching cam timing (in general)
: two years ago I became aware that
: several U.S. cam grinders provide a cam
: card that specifies a certain number of
: crank degrees with 0.050" of lift.
: Their reasoning was that at
: 0.050" the slope of the cam lobe
: is such that you get much more accurate
: measurements and settings. However, I
: have never seen the equivalent data for
: Triumph or BMC cams. I will inquire
: with a couple of friends if they have a
: copy of the book you referenced.
:
: I think I have seen the Crane PDF
: before. Note that is says the second
: common method of setting the cam is to
: locate max lift on the inlet lobe which
: is what I have been trying to do.
: Their argument against it is that not
: all cams have a symmetric profile. If
: the Triumph cam I have is stock it
: should be symmetrical. Without doing
: the math, the profile looks symmetrical
: in my chart.
:
: Assuming I do have a stock cam and that
: its real duration is about 256 degrees,
: then the duration would have to have
: been checked/measured somewhere between
: the 0.010" and 0.015" of lift
: you mentioned. That matches my chart
: pretty well.
:
: As I said earlier I'm going to put the
: old timing parts back on tonight and
: see where the cam was timed before I
: took the engine apart. If nothing else
: I will duplicate that setting. The
: engine ran like a top before I damaged
: it.
:
: Thanks again. I do appreciate your
: help and comments.
: Doug
:
:
:
: --Previous Message--
: Ken Balls Autobook is where I got the
: spec.
: Here's a link to Crane Cams PDF on
: setting cams.
:
:
: http://www.cranecams.com/uploads/instructions/803_.pdf
:
: Yes in this case, the events are based
: on the tappet beginning & ending
: when it's .040 off the base circle.
: Note that in the Crane reference, they
: call out .050 tappet rise. That is
: determined by cam grinder. Some
: advertise a lot of duration but it
: might be measured at .015, whereas a
: cam with less advertised duration might
: actually have more, if it's measured at
: a larger tappet rise number.
: Simple now right?
: Glen
:
:
:
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