That's what .050 is for. Compareing the advertised, you have to look at the points and understand what or how much a difference .004 and .006 will make.The reason you cant use duration to compare cams from maker to maker is that they all measure using different start and stop points.
I keep this in mind when looking at cams for what kind of rate of lift they have, but that is only part of the story.
Your answer is your on description below.How can I have valve float at idle? If it can happen at any rpm it's more like harmonics.
Ummmmm, yeeeees, but, since springs have a life span and wear out, get weaker, the ceiling of the RPM limit drops. So metal fatigue is an issue. Fast rate cams will wear on a spring harder.Valve float is most accurately described as when the springs are overcome by high engine speeds.
YES! Absoultely! Now comparing manufaturer vs. manufacturer, you gotta have a decently good understanding of this whole thing. Like I said above, the difference between measureing a cam at .004 and .006 even on the same cam will or should show a big difference. Now how big is also dependent of the cams profile. What it is used for. Nevermind manufacture to manufacturer. But it still applies.So when comparing cams from the same manufacturer you could use duration.
IF I had a machine to measure such super small things, I'd ask everybody to send me a cam to measure so I could post the results.
That would be interesting.