I am curious about advanced duration, For an example you have 2 cams with almost the same lift and duration at the 50 but the advanced cam duration is really different from one another, How does that work? :confused: ...mike

Originally posted by 69ralleygreen:
I am curious about advanced duration, For an example you have 2 cams with almost the same lift and duration at the 50 but the advanced cam duration is really different from one another, How does that work? :confused: ...mike =
Not sure if I understand your question but I will give it a try ;)
A cam that is advanced means that it is installed with the intake centerline x amount of degrees from the lobe separation angle.
In other words, if the LSA is 110 & the intake centerline is installed at 106 ATDC the cam is advanced 4 degrees.
If it were at 110 the cam would be "straight up"
All else being equal if the cam is advanced it SHOULD improve low end power slightly with a reduction in top end power.
It is almost always better to install a cam advanced rather than retarded which is why most cam manufacturers have advance "ground into" the cam.
This means the lobes are advanced relative to the device that locates the cam (the pin for a Chevy)

Wolfplace, Thanks for the reply, What i meant was the (advanced advertized duration) not the install, 2 cams close in lift and duration at the 50 but one cam has a higher advanced duration, The other alot lower? Buy the way i love this: ("Life is tough.,, Life is even tougher if you're stupid.") THATS SO TRUE thanks...mike

What do intensity numbers mean? Harvey Crane created “intensity” as a means of comparing the ramp designs of camshafts. Lower number are usually preferable but can be harder on the valve train depending on the entire lobe design.

Hydraulic intensity is the difference between .004 duration and .050 duration.
Minor Intensity is the difference between. 010 duration and .050 duration.
Major intensity is the difference between .020 duration and .050 duration.



http://www.camcraftcams.com/catalogs/taylor_profiles.html


Performance cams usually have much lower intensities than their milder counterparts. The long ramps lower the effective compression and result in quieter operation.

Different cam companies rate the advertised numbers at differing lifts. For instance Comp rates the adv numbers at 0.006" lift. Crane rates theirs at 0.0045". SAE is another one altogether. So that makes a difference. Also some profiles are more aggressive, and are "faster" from adv to 0.050". Comps XE's for instance are very aggressive and fast compared to some of the older profiles.

70gs455, that makes sence...mike

Originally posted by 69ralleygreen:
Wolfplace, Thanks for the reply, What i meant was the (advanced advertized duration) not the install, 2 cams close in lift and duration at the 50 but one cam has a higher advanced duration, The other alot lower? Buy the way i love this: ("Life is tough.,, Life is even tougher if you're stupid.") THATS SO TRUE thanks...mike =
Ok,,, What you are referring to is advertised duration vs .050 duration, not advanced duration & it was explained pretty well above.

Just for info, faster is not always better,, especially if you cannot control the valve action ;)
Just went through this with two different brand a hyd roller lobes & although they both made very close to the same power one would not go over 6100rpm with almost 450lbs total spring & the other went to 6400 with 350lbs & would have gone further :(

Thanks wolfplace, Have a great holiday...mike smile.gif

This is partially why roller cams and solid cams excel over just hydraulic cams. You figure if your two cams have the same .050, but one of the two has less advertised duration, like it was explained above, that would usually indicate that the lobes are more aggressive on the cam that has the same .050 duration but less advertised. The aggressive design opens and closes the valves at a faster rate. The faster rate of opening and/or closing can build more area under the lift curve, and as long as the valvetrain can take it, this can build more power than a lazier camshaft with seemingly similar cams. Roller/solid cams can use even more extreme lobes than a hydraulic cam, cause due to their lifter design, they can handle it better. Like Mike was sayin though, its still not all black and white. Reguardles of the lifter type, you can still encounter valve float problems moreso than a another seemingly comparable camshaft, depending on the total specs/engineering of that cam.

Thanks greg, I think i pretty much understand this better now, What do you mean if the valve train can handle it, I just had a pro valve job done with all the good stuff so i dont have to worry about that, Anything im missing i should know, Its a solid lifter ud harold recommended 296/304 f10 ...mike

Well here is what I mean. Assume you have valve spring rated for .500 lift, yet your cam is making .550 lift. Thats a dangerous situation where the valvetrain wont be able to handle the cam and bent or broken pushrods and other valvetrain hardware due to coil bind can come from a situation like this. To explain it further, its not just the lift that matters, but seat pressure and open pressure matter too. Pretend you have a hydraulic cam, not a solid cam. Also pretend that the hydro cam has .550 lift and you have the proper valve springs for a hydraulic cam of at least .550 lift(so they dont bind) and everything is working good. Than say you changed the cam tomorrow to a solid cam, also with .550 lift. Even though the specs seemingly dont differ by a whole lot, and the valve lift is the same, the valve springs probalby wont work out any more though. The solid cam is capable of a more aggressive lobe design(faster ramps), so it would require a stronger valve spring, even though the specs look very close between the two cams. And even though it can handle the valve lift, witout the additional seat and open pressure, the valve spring will have a difficult time controlling the valve. And having the valves bounce off the seat uncontrollably isnt exaclty a recipe for good engine power, so thats why the proper hardware and valvesprings are important with a cam choice. The valve job itself doesnt really have anything to do with keeping the valve under control, but when you say you have all the good stuff, I assume that this means good rockers along with good/strong studs and the proper springs for that cam and everything else. If thats the case than you should be smooth sailing.

Yes, just had all that done, In fact you know that scorpion rocker company, Thats were i had my machine work done, They took me for a tour on making those rockers, It was insane, You can eat off the floor its so clean, And they showed me the difference between there rockers and crane golds, boy they really make a better rocker, I bought a set to...mike