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Discussion Starter · #21 ·
Okay. I get it.
Now, how about Timing. Many of you refer to "advancing" spark timing as "adding timing" which is totally incorrect

I can "add timing" two ways...retard or advance, but can only "advance" timing one way.

Capeesh ?
Hear it all the time . "Try giving it "some more" timing. Never thought about it but yeah I guess that is incorrect.
It should be just "advance the timing " or "retard the timing "
Buddy of mine been playin around with chevy engines 25 plus years but has always had some sort of mental.block when it comes to which way the distributor gets turned for advance or retard . Finally one day hes fumbling around and saying "I always forget, which way is it again??"
I said "ITS CLOCKWISE RETARD !!" lol
guess what ? He never forgot since.
Funnier part of the story is that his last name is klock haha
 

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Totally semantics but hey if nothing else the thread may prompt a less experienced guy who's thinking about changing his cam to really think about what hes doing and why .
Yep, I agree
 
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Time is measured is degrees of the earth's rotation, is it not?
No. Movement is relative to time. Every book in math, science, physics, etc... measures time in seconds, minutes, hours, etc...
 
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The duration(ammount of time)that the valve is open on a 230 @ .050 cam is less than the the duration (ammount of time ) than if a 270 @ .050 cam is used.
It takes a longer period of time for the 270 cam to open the valve to .050 lift than does the 230 .
As relative to one another the word duration is being used correctly there but to isolate it and say its a "230 "duration " camshaft " is actually incorrect isolated like that .
Semantics
.
The amount of "time" the valve is open is variable based on the RPMs of the engine/cam.

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All of which were derived from degrees of earth's rotation as recorded by the shadow lines on sundials.
The 24hr standard was derived from one rotation of the earth yes, but we are talking about a crankshaft, not the earth,, and the number of degrees movement in the duration (time) of the valve event.

Because time of the event is variable with rpm, the established constant is referred to as "duration" in degrees. Again, semantics, but I get what you are saying.
 

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I'm making the case that whereas the definition of duration, as mentioned earlier, is a measurement of time:

That time cannot be divorced from degrees of rotations since the measurement of degrees is the progenitor of the measurement of time.

Consequently, duration is a correct term for measuring camshaft event values.

That being said - the term "dwell" could also be correct as it is used for the measurement of degrees rotation of a distributor shaft for the assignment of a value to the making of an electrical circuit
 

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Discussion Starter · #31 ·
I'm making the case that whereas the definition of duration, as mentioned earlier, is a measurement of time:

That time cannot be divorced from degrees of rotations since the measurement of degrees is the progenitor of the measurement of time.

Consequently, duration is a correct term for measuring camshaft event values.

That being said - the term "dwell" could also be correct as it is used for the measurement of degrees rotation of a distributor shaft for the assignment of a value to the making of an electrical circuit
"That time cannot be divorced from degrees of rotations since the measurement of degrees is the progenitor of the measurement of time"

I disagree. A measurement of degrees can be divorced from a time frame. One is a distance and the other an ammount of time. Not only can it be but it absolutely is in this instance because there is no time frame (duration).
The time frame (duration)is a variable here . . It varies therefore the degrees in which the crank turns as it relates to the position of the valve has nothing at all to do with a fixed time frame (duration)
 

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Precisely . Variable .
So mathematically no biggie : DURATION = (duration as measured in degrees/360 ) X time event. You pick the time event OR set it to 1. That's how the math works I'd think. A fraction (arc) of the time event set to 1. Or maybe X 100 actually ?

PS Harold Brookshire taught me to try and get .200" duration ( at a time of 1 !! ) "arcs" and compare them to the 0.050" duration "arcs" to judge intensity. Plus as 68 states, the ADV duration has to do with take up ramps, etc, and gets to be a wonky number to compare with.
 

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If I get summoned for jury duty, and I get seated on a jury, I am committed to jury duty for the DURATION of the trial, even though the TIME commitment at that point (in days, hours, minutes) is unknown. Duration in that context is defined as "from beginning to end" just as 240 degrees camshaft duration is "for 240 of the 360 total degrees rotation", regardless of how fast the crankshaft is spinning. Just sayin'...

Stated another way, if I get seated on a jury, and I asked the judge how long I'm going to be here, and he says "for the duration of the trial" do you think it's a good idea to tell his honor that I'm going to need to know exactly how long that's gonna be? :)
 

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So mathematically no biggie : DURATION = (duration as measured in degrees/360 ) X time event. You pick the time event OR set it to 1. That's how the math works I'd think. A fraction (arc) of the time event set to 1. Or maybe X 100 actually ?

PS Harold Brookshire taught me to try and get .200" duration ( at a time of 1 !! ) "arcs" and compare them to the 0.050" duration "arcs" to judge intensity. Plus as 68 states, the ADV duration has to do with take up ramps, etc, and gets to be a wonky number to compare with.
That's why roller cams are so good, more area under the curve with a higher intensity at .200 lift.
 
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