too mild camshaft

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Really Fishy68, we're talking semantics here. The thing is, you measure valve lift in inches and cam duration in degrees... I think we both understand exactly how a cam/lifter/pushrod/valve combo works...it's our explanation that varies.

Even though the "at .050" lift" number will be higher at the valve when increasing the rocker ratio, it does not increase the duration. The duration at .050" number is the only
one that moves around, and it does so with no effect on overall duration.

I think we actually agree here.
 
At the valve, where it really matters, duration increases slightly when rocker ratio is increased.

Have fun with it.
 
Cracked back, you are not geting the point....at the valve LIFT increases.
How much lift at a particular duration changes because you have more lift at the valve at the same duration measurement. You don't measure duration at the valve. Duration is measured in degrees. Valve lift is measured in inches. The numbers do correspond but not in the way it has been described.
the whole purpose of "advertised" and "at .050" lift" numbers is to give you an idea of how aggressive the lobe is. There are plenty of cams out there that have seemingly identical lobes when you compare the advertised duration, but the at .050" number tells the rest of the story. this is why you have cams designed for less endowed engines (smaller diameter lifters) and cams designed for big manly mopar lifters!

I don't know how else I can say it. A rocker arm can not and will not effect duration. It effects lift only. The at .050" measurement with the increased ratio rocker arm will widen the at .050" lift number in degrees ONLY because the valve is opened further, faster in relation to cam rotation. It has no effect on overall duration.

Check out this chart...you will notice that they don't even list the change at .050" lift duration, only lift, when comparing different rocker ratios on the effect of lift at the valve. The at .050" change is not worth measuring because it is inconsequential.....unless you are straining the limits of lifter diameter.
http://www.oregoncamshaft.com/Hydraulic-Cam-Specs.html
 
fishy68 said:
Sorry but a higher ratio rocker does affect duration at .050 a little due to bringing the valve up to .050" lift quicker. It would also have to affect the total duration since it's rate of lift is faster. Although it is so minimal it probably wouldn't be noticed.
Click to expand...

Yep. The area under the curve HAS to increase, when increasing rocker ratio...
 
this one was dead 3 weeks ago! LOL

the duration doesn't change, only the lift at a particular duration....a 268 cam is still a 268 cam regardless of rocker ratio.
 
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