anesthes wrote:
The second cam has a faster intake ramp, but they are both penuts.

-- Joe

rklessdriver wrote:
I don't think either of them will have any kind of a lick at idle, so power brakes and driveability will be good. If I had to pick between the (2) I would run the second cam.

The second cam has far more lift and slightly longer lobe centerlines so it SHOULD have a wider powerband by maybe 2-300RPM over the first cam.

The first cam has a few degrees more seat timing but the ramp has a slower rate of lift and the lobe is not very big lift wise. It will make less peak HP/TQ on the order of 10-15 probally. It'll be down on power across the power band as well and you don't gain ANYTHING in driveabilty over the bigger second cam.

Of these (2) there is no reason (unless you just want less power) to not run the second one.
Will

rklessdriver wrote:
Joe - I'm not following your comment about how a cam with less lift usually has the faster rate of lift.

rklessdriver wrote:

You would have to break things down with a dial indicator and a degree wheel to map out every degree of lift/duration between 2 cams but I'm positive the cam with more lift will win on rate of lift every time - provided the duration of the 2 cams your comparing (such as in this case) are close to one another.

rklessdriver wrote:

I'm not trying to insult you with my (following) simplified explanation but I think it may help others understand what I'm talking about.

The first cam has an Intake lobe with 264* (out of 360*) advertised duration. It has 210* (out of 360*) of duration remaining after the lifter has acheived .050 lift. In that 264* it is only capable of .318 lobe lift and back to 0 (well .020 or .006 or whatever they use for advertised duration).

The second cam has less advertised duration to begin with at only 260*... It also has the same 210* of duration remaining after .050 lift. In only 260* of duration the second cam reaches .350 lobe lift and back to 0....

You were right the first time. The second cam has the faster rate of lift on the intake lobe. Not sure if you mispoke or what in your last post.

rklessdriver wrote:

For everyone else who may be lost:

First thing you have to know is that cam lobes only have 360* of rotation to get everything done (valve closed, valve opening, valve max lift, valve closing, valve closed again).

Timing events on a cam lobe are measured in "degrees of Duration". The total amount of time a lifter is off the heel of the cam or in positive lift (be aware that this point is measured differently by different cam grinders) is refered to as "Advertised Duration".

Because .000000 lift and .0000001 lift is really hard to detect and repeat, cam grinders long ago started using .020 or .006 lift (it is a more repeatable measurement) as a place to start measuring for the Advertied Duration. It casues alot of confusion, but it's an important measurement and these days very overlooked and misunderstood.

There are a host of other cam lobe timing measuerments for people to look at. Duration at .050, .100, .200 ect. They are smiply the remaining degrees of duration (remaining from your orginal 360*) at a given amount of lift. None of them mean anything unless you correlate them to the advertised duration. Then you can compare 2 differnt cam lobes by looking at and comparing all these timing numbers.

Now I'm only talking about individual CAM LOBE timing events here. They are very simple to understand compared to...

rklessdriver wrote:

Actual entire camshaft and valve timing events, which are a product of the cam lobe timing events combined with the centerlines the cam lobes are ground on (in releation to the crankshaft)and rocker arm ratio. Valve timing events are measured by degrees in releation to the piston being at TDC or BDC of it's stroke.

You almost always see the intake lobe centerline and lobe seperation on cam cards. Lobe seperation is nothing more than the intake & exhast centerline numbers added together and divided by 2. Some people put so much emphsis on it... I have no idea why. It really dosen't tell you that much useful.

rklessdriver wrote:

You sometimes you see the valve timing numbers on cam cards. These are very useful if can comprehend what is actually happening at those given points in a 4cyl engine. It's important to know how long the valve is actually off its seat when the piston is still on the up stroke and how long it continues to be open after the piston has gone past TDC and is approaching BDC. Same for the exhaust valve and for when the plug fires.

dan0617 wrote:

Make SURE your heads are set up to accept the valve lift you are throwing at them. I didn't check, they may be able to in their out of the box configuration, or maybe not. Make sure before you buy the cam if you don't plan on doing any head/valve work.

BeachBum wrote:
speed is addicting....

BeachBum wrote:
Your two cams above are fine to run with .575 springs.... I always look at the lobe lift and then can easily figure out how much rocker arm I can from their. You have a very common .350 lobe on that second cam....multiple that by 1.6 and you have your .560 lift.... with room to spare.

pr0zac wrote:
i don't think that xfi cam will be ok without beehive springs although its a way better choice than the first.. even a cc304 is a very very small cam. i think that the second cam will give you more cause of all the lift that it has.. i don't really like the xfi cams. i think you should go custom. it will give you a better result by being able to tell them specifically what you want.

PeteK wrote:
#2

RedGut86 wrote:

I take it you are using the duals that come on the head right?

pr0zac wrote:
i am going to go ahead right now and say i told you so.. i have read numerous post about valve control issues with xfi lobes and motors being down on power because the xfi cams weren't matched with the lighter weight beehives springs. i don't think that the springs that come with the heads are going to be enough. the cams were specifically designed to be run using beehive springs and only those springs.