Look at swapping springs every so often with fast ramps and absurdly high lift cams. The Crane 832 duals are good springs!!!

 

Speaking of "accelerated lift" lets take a look @ Vinci why don't we.

Lets do a comparo and see how true this is

Comp 224 .581(x-er) vs Vinci 224 .585(al)

Comp
224 @ .05
146 @ .20

Vinci
224 @ .05
146 @ .20

 

You can't compare different manufacturers cams with published specs.Back in the 60s NHRA ran a stock class using OEM published cam specs checking the lift and duration at those points.Competitors who ran stock cams had no chance against the "stock regrinds"that had faster ramps.The regrinds had more usable duration by having higher lifts on the the acceration and deccelaration ramp and peaked at the maximum legal lift.Some of those cams looked like they had square lobes,some wouldn't idle at all,they often broke the valvetrain,but a competitor could pickup 50hp+ on a big block Chevy,Ford or Dodge.

 

I found this to be an interesting read:

These days everybody wants more: Bigger, "Fatter Intake Profiles, yielding more "Area Under the Lift Curve" and Higher V.E. (Volumetric Efficiency). Some Racers mistakenly believe that a more aggressive roller camshaft requires a visit to one of the cam companies struggling for recognition, who push alternative cams with cute names like "Inverted Radius" (Actually a Re-entrant, Concave or Hollow-Flank profile Cam). Unfortunately these cams are not a wise choice considering their major drawback: the undesirable hidden side effect of reduced valve train life expectancy! Subsequently, many who purchase these cams learn to live with problems like broken or prematurely worn-out valve springs, "dropped" valves, bent pushrods, etc., unaware their valve train has been "Jerked" around by a camshaft of reduced stability at higher RPM!

These cam grinders are not however solely responsible for promoting misinformation about these so called "Inverse Radius" Cams. With the aid of the computer and the addition of new tools of the last decade or so such as the "Cam Doctor" "Audi Cam Pro" etc., Cam Profile Dynamics which were once the privy of cam designers alone can now be viewed by many others. With this new technology, there has been a new crop of "experts" who love to talk Cam Profile/Valve "Dynamics".

I am often amused by the cavalier attitude of some of these neophytes who seem to have this view when it comes to Valve Acceleration & Jerk Curves: "The more radical looking they are the better". Well, pardon me for saying so but to paraphrase conservative columnist William F. Buckley, "Ignorance Is Not A Virtue". The only time you should want your 2nd & 3rd differential curves (Acceleration & Jerk) to have greater amplitude or to have the "look and feel" of "Radical" is when you're dealing with limited RPM levels.

It is no coincidence that industrial engine production cams such as those manufactured by John Deere, Caterpillar Tractor, Allis Chalmers etc. are designed in this manner. They are low speed engines! (Have you ever heard of anyone running one to five or six thousand RPM?) They are the cams with the familiar hollow or concave flank and whenever you see one of these cams, remember: Their physical appearance is the result of their High Acceleration & Jerk Peaks and such characteristics are always associated with more moderate (not higher) RPM levels! These inverted looking cams will give you a slight torque increase because they will usually have 2-4 degrees less seat duration for a given duration at .050" lift. The problem occurs when you try to run such cams at up to 8000 plus RPM where they do not belong. It is simply a case of "Nada Por Nada" as they say in old Mexico. You don't get something for nothing. Those who can limit such cams to say 7000 or so maximum RPM and have appropriate valve train components won't fair too badly, but those who insist on consistently running cams like these at Higher RPM levels is "Rolling the dice" every time they does so. They should therefore not be too surprised when the dice on occasion roll "Craps".

 

I think we need to define accelerated lift and when it becomes to drastic or extreme, obviously max lift on an aftermarket cam is achieved more quickly than a stock cam. There have got to be different degrees of accelerated lift. Is there a way to measure the mean amount of air that is taken in on one valve duration (opening and closing). Im assuming more accelerated lift means more air has the possibilty of entering, theres got to be some factor of deminishing returns here, where no matter how long the valve is open an engine (on an certain displacement) that cylinder will not be able to use any more air. So wouldnt an ideal cam be one where the acceleration of lift is fitted to the engines displacement?


Im not a cam expert by any means, just thinking out loud

somebody correct me if my thinking is off

 

Whitt,

If they are making a claim and it doesn't hold true....not much else to say, but I do understand your point. Also, another interesting tid bit. Notice, Vinci is the only to measure seat duration @ .004.

Grip,
What motor is his writing directed to?


You have forgotten about head flow.

Of course. To large of a cam can hurt an engines performance. Especially a street engine, where low end performance is sacrificed for high end, leaving no acceleration.

 

Sprtside 5.3,almost all manufacturers give duration at .004" that's known as advertised duration and they also give duration at .050" to compare grinds within their lineup.Vinci is not doing anything to deceive anybody advertised duration is actually useful to someone calculating valve overlap.