Built LT1

iTrader: (3)

In respect to duration, the approximate relationship between advertised duration and the duration at .0050 is usually relative. For example, a cam with an advertised duration of 260 might have a duration of 210 at 50 .0050, and cam with an adv duration of 290 might have a duration of 240 at .0050.

So my question is what happens (results in performance) when comparing two cams that do not follow this relationship?

Cam A: Larger adv duration than cam B, but less duration at 50 than cam B.

Cam B: Smaller adv duration than cam A, but more duration at 50 than cam B.

Which cam is bigger? How will each one drive as well as perform?

Thanks in advance to those who respond.

Jakes Dad

is this a test? I am not intelligent, but I've learned to surround myself with folks that are. On the flip side I am smart enough to think the best place to receive the correct answer would be going directly to a cam manufacturer. I've found them to be very helpful provided you tell them exactly what you want.

Razor_Blade

iTrader: (8)

The difference in advertised and .050 duration is known as the lobe intensity. Assuming that both cams advertised numbers are measured at the same point, the one with fewer degrees of difference between the advertised and .050 numbers will have a more agressive ramp profile.

Using your A and B cams as an example.

Cam A: 284 Advertised and 228 @ .050 = a lobe intensity of 56
Cam B: 280 Advertised and 230 @ .050 = a lobe intensity of 50

Cam B would be generally considered to be the better cam.

Beast96Z

iTrader: (21)

You also need to look at the lobe duration at .200. Take for example a XE-R vs. a LSK lobe. A givin XE-R lobe will have a diffrence of 49 between advertised and .050". A LSK will have a diffrence of 50 between advetised and .050". You would automatically think the XE-R is a "faster" lobe, but in reality, the LSK is actually 4 degree's larger at .200 than the XE-R. This makes it faster to a point, then lets the valve back down easier onto the seat. You need to look at the duration at as many point as possible to determine which cam is "larger", but also to find were that cam is "larger" at.

Built LT1

iTrader: (3)

So Cam "B" would be the better cam for performance with more lift under the curve. Would cam "B" also be bigger? Which cam would rev higher?

Built LT1

iTrader: (3)

So does this mean that the more aggresive cam with a smaller advertised duration rev out less than the other one while producing higher numbers in the power band?

Assume same motor platforms for theoretical comparison.