1.7's....
- Thread starter casper98gt
- Start date
dragnazz5.0
My "0" key d0esn't w0rk, s0 I have t0 use the zer0
well ive never measured anything to see for myself that it changes but i had this conversation a little over a year ago with an engine builder who has built engines for nascar teams for 25 years, and with a nascar head porting guy and both of them agreed that it does change.
dragnazz5.0
My "0" key d0esn't w0rk, s0 I have t0 use the zer0
degrees of crankshaft travel (rotation) while the valve is off its seat.....usually measured from .050"
There is the total duration (advertised) which is the very instance the valve opens, and the very instance it closes, like with an E-303 cam of 282 degrees. That will always remain unchanged no matter what ratio rocker you have. When you start measuring duration at .050 lift or anything other lift, that is where you will see the small differences. Like for the E-303, the 220 degrees measured at .050 will increase by a couple degrees.
Yep,
It's all in how one defines duration.
(it seems you understand what Jay would have been getting at...
)jason
Yep,
It's all in how one defines duration.
(it seems you understand what Jay would have been getting at...
jason
Hehe, I wish that were the case. That is how I defined it to him, and he still told me I was wrong. I presented the facts of it from a pontiac website and he didn't even look at the site and just started badmouthing me telling me how wrong I was. He said only lift is effected, even though some duration numbers are measured at certain lifts. He seemed to have quite an attitude about it. Needless to say, I won't be buying any camshafts from him.
I did buy my cam from Jay Allen 
and plan on buying more from him...
I would recommend his services to anyone...
(I will NEVER buy from 'the other guy')
Mechanically speaking,
A rocker arm ONLY multiplies the lift. The rocker arm cannot physically affect the duration.
A rocker arm ONLY changes the lift; it is a "lift multiplier".
You are imposing your definition of 'duration' when referring to the affect of rockers.
In doing so, the word 'duration' loses some of its meaning.
Jay seems to define duration as 'seat-to-seat'
You (and others) seem to define duration as .006", .050", etc.
Think of it this way...
Does valve overlap change?
Does the timing of valve events change?
If overlap remains the same, and the events have not changed,
then how can the duration have increased?
Just a different way of looking at things...
jason
and plan on buying more from him...
I would recommend his services to anyone...
(I will NEVER buy from 'the other guy')
Mechanically speaking,
A rocker arm ONLY multiplies the lift. The rocker arm cannot physically affect the duration.
A rocker arm ONLY changes the lift; it is a "lift multiplier".
You are imposing your definition of 'duration' when referring to the affect of rockers.
In doing so, the word 'duration' loses some of its meaning.
Jay seems to define duration as 'seat-to-seat'
You (and others) seem to define duration as .006", .050", etc.
Think of it this way...
Does valve overlap change?
Does the timing of valve events change?
If overlap remains the same, and the events have not changed,
then how can the duration have increased?
Just a different way of looking at things...
jason
All of that looks very similar, off another 'particular' site.
Judging duration from .006 (less accurate) and .050" are general numbers that are fairly easy to compare, from cam to cam.
As long as we do not misinform, I believe it is okay to generalize for most of our purposes.
After all, we are not custom cam grinders and it is not our job.
I do believe that a person should explain their 'facts' or 'opinions' in a constructive manner. If they persist to slam someone, that is not very professional in my opinion.
I had NO problems with Ed or his personality except on a couple isolated occasions with someone else. I have seen much more arrogant problems with the 'other guy'
But like I said, they both got different ways of doing things, and they both know how to get an engine to do what they want it to do
Judging duration from .006 (less accurate) and .050" are general numbers that are fairly easy to compare, from cam to cam.
As long as we do not misinform, I believe it is okay to generalize for most of our purposes.
After all, we are not custom cam grinders and it is not our job.
I do believe that a person should explain their 'facts' or 'opinions' in a constructive manner. If they persist to slam someone, that is not very professional in my opinion.
I had NO problems with Ed or his personality except on a couple isolated occasions with someone else. I have seen much more arrogant problems with the 'other guy'
But like I said, they both got different ways of doing things, and they both know how to get an engine to do what they want it to do
I disagree that I am merely imposing "my definition" of duration.
When I look at a cam card, it gives me multiple measures of duration. Typically, one that says "advertised" and one that is "measured at .050 lift". The cam grinder defines duration as measured at a specific lift and overall as the valve events happen, such as the overlap. I think the problem is making the distinction of know that it does not affect ALL duration, just the duration measured at any given lift. That is not matter of perspective or anything, those are just the facts of the cam profiles.
In a nutshell, I am using the definition of duration that appears on the cam card, not my own.
When I look at a cam card, it gives me multiple measures of duration. Typically, one that says "advertised" and one that is "measured at .050 lift". The cam grinder defines duration as measured at a specific lift and overall as the valve events happen, such as the overlap. I think the problem is making the distinction of know that it does not affect ALL duration, just the duration measured at any given lift. That is not matter of perspective or anything, those are just the facts of the cam profiles.
In a nutshell, I am using the definition of duration that appears on the cam card, not my own.
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