If a 288/296 is too much for a 496 (another post today), I think I just bit off more than I can chew smile.gif
if two solid cams have roughly the same .020/seat/advertised whatever its called duration, but one of them has substantially more .050, what is the net effect here? I know the engine 'sees' alot more duration, but wouldn't the advertised determine more of how a cam makes the car idle/behave and whatnot? but I know the rule of thumb is to keep it under 250 @ .050 for a streetable car.. I know its a sort of basic question, but I am just trying to compare, in a way, the cam my cam swap person picked and a XR286R:
mine: (CR lift rule)
287/291 @ .020 256/260 @.050 172/175 @.200 .643 .643 (on a 113)

XR286:
286/292 @ .015 248/254 @ .050 170/176 @.200 .653/.660

My engine is going up on the dyno tomorrow, I am going to get some digital footage of the dyno runs, if I can get my new domain name/site working, I'll be sure to post it.
I had called comp cams a few days ago because I was (am) uneasy about the choice, and talked with them about the intensity of the lobes, and the guy on the phone said it was 'roughly similar' to the intensity of the XR lobes, and "certainly not the most intense stuff they have," but "not the mildest either." I guess its sort of subjective anyway.

matt

In my opinion, I would always go for the most intense cam (seat duration minus duration @ .050) that I could use for an engines intended usage.

A lower number for intensity (31 vs 40), equals more power when comparing two cams with the same advertised duration.

For example the first cam you have specd out has an intensity of 31 degrees intake and exhaust. The second cam has an intensity of 38 degrees.

However, between .050 and .200, the second cam is more intense than the first. This intensity is more in the range of where your heads are going to start to work. Between .000 and .050 there really isnt a whole lot of air coming into or flowing out of the engine like there is between .050 and .200

By having a more intense cam, you're basically opening the intake at a faster rate and keeping it open longer given the same advertised duration. To me this equals more hp/torque without losing much if any cylinder pressure and drivability. Note that I didnt say opening the intake sooner, because that would indicate a larger duration (not taking into account ICL)

You have to also remember that not all cam companies list their advertised duration at the same spec, some may list it at .006, others at .020, etc.. So just looking at two cams on paper does not mean you can compare them. This whole intensity deal isnt an exact science, but if you have measurements taken at the same point on two different cams, you can at least make an educated guess as to how they will compare to eachother.

I would vote for the second cam, because I think it will be more streetable (although I dont know the LSA) while possibly making more power than the first grind. However this just a guess because I do not know at what point the larger duration of the first would overcome the power output of the more agressive lobes of the second cam.

Just some observations, I'm no expert - just some punk kid learning as I go. graemlins/thumbsup.gif

I am no cam expert by any means but to me the XR cam from Comp looks alot more aggressive than the larger cam (brand ??).

If you look at the duration at .200 on both cams they are very close to one another. First cam is 172/175. The XR cam specs at .200" is 170/176, this is with 8 degrees less on the intake and 6 degrees less on the exhaust at .050". To me the XR cam looks quite a bit more agressive of a cam than the first one.

IMO, I think I would go for the smaller XR cam if you are worried about streetability.

Not if the Comp is set on a 110lsa it won't.

Gene not to be a knucklehead, but I can't figure out what you mean? not on a 110 it won't what? be more aggressive?

matt

well here we go again, REMEMBER that the more intense the cam lobes are the more valvetrain noise you get. example: valves slamming shut! And from what ive gathered possibly bouncing. This equates into lower valvetrain life. and surely is rough as all hell on your seats. yes a more intesnse lobe will make more power, no doubt, but how much power is it worth to bang the hell out of your valvetrain. I know i know "YOU" or Joe X, or whoever have been running comps___XE cam for X,XXX,XXX miles with no problems. Thats fine but there are negitives to the "super" intense lobes. Just a thought.

Certainly, the slightly larger cam on 113 LSA would likely be more 'docile' than a more intense, albeit slightly shorter on the seat lobe on a 110 LSA. Better idle, etc.

My experience is that wide lsa's don't help charge velocity much. But they are more docile street cams.

I am concerned about valvetrain life b/c when you get past the CC magnum lobe grinds, it states right in their cat. that you are getting into aggressive lobe territory that TO ME means shorter valvetrain component life b/c of them getting beat up more!!

As for the wider LCA thing, I figure it is an overlap thing.

Closer LCA to me means peakier power curves along with more "lope", whereas wider LCA to me means lower, but broader power curves along with a smoother, less noticable lope...

All this is why I'm moreso into the old fashioned CC, HE, Magnum and GM's stock hi-po grinds then the newer aftermarket, high-zoot stuff b/c I sure don't want to have to do all of it again if the valvetrain gets beat up......

And I would very inclined to listen to Harold's cam's life recommendations concerning his and now Lunati's cams too....

pdq67