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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