Aren't there two measurments for cam duration? One's called
"advertised" (I think) and the other is measured from 0.050" of lift on
both front and rear slope (forget the name for that, if there is one).
It seems measuring at 0.050" would remove the valve train "slack" from
the measurement, giving a somewhat more accurate measurment.
I think the BJ8 cam is 255deg or thereabouts measured at 0.050"
of lift.
bs
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Bob Spidell San Jose, CA bspidell@comcast.net
'67 Austin-Healey 3000 '56 Austin-Healey 100M
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> Hi Dave,
> I'll agree with you on the enhanced gas flow but I'll still maintain my
> opinion on valve speed. Total duration (the valve leaves the seat and then
> returns to the seat in crank degrees) does not indicate how many degrees the
> cam is at full lift. It all depends on how aggressive the ramps are on the
> lobes. If a 265 degree cam has 65 degrees at full lift that gives 100
> degrees to get it either up or down. If a 290 has 74 degrees full lift, it
> takes 108 to go up or down. In this case, the 290 valve is at full lift
> longer but it has more crank rotation to rise and fall, so the valves would
> move slower given the same lift. Increasing dwell or lift can make the valve
> accelerate faster not necessarily duration.
>
> Respectfully,
> Greg
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