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[MCE]

the difference in .006" and .053" duration on two lobes with the same .053" duration could well differ by 6 or 8 degrees.

Not really.

But It really doesn't matter. There's virtually no flow going on below .053, and even
if there was, it's not going to be significant enough to make any difference one way or
the other.

I don't get why you're so hung up on what goes on under .050 lift. It's called the lobe flank and
there's little to nothing happening there!!! (Thats why they wait to start measuring at .050,
measuring at .006 just gives a false illusion of more duration (no real flow happens until over .050
at least on an intake port. EX is a little different, but not all that much)

[MCE]

Flow a port at .006" lift one time. There ain't much of anything there. No real flow
happens below .050 (give or take). So any advertised duration taken at those lifts
is meaningless. .050 is just a number they picked out of thin air and everyone
follows that recommendation.

Kinda like flowing ports at 28" of depression. That too is just a number that everyone
agreed to use, so things would be 'pseudo-standardized'.

[Nocvo]

Even with more data points in the cam description it still won't tell the average punter bugga all, horses for courses so choose wisely or ask the right people.

[prodrag1320]

I designed my cams in my fuel bike,did a good job I guess,fastest in the world & first in the 6`s (6.85)

[grc]

I may have misconstrued what the OP was saying, but I took it to mean the interest was more about the severity of the closing and opening of the valves (which is a big issue on stock TC's IMHO), and not about duration.  The profile of the ramps isn't something you can easily discern from any of the specs commonly listed, so someone seeking to find a cam with less severe ramps can't just compare specs.  Of course I could be wrong about the intent of the OP, if so please ignore this post.

JMHO - Jerry

[dave brode]

Thank you, Jerry. You are correct. Example, 252* is a popular intake duration. The chance of every 252* lobe having the same seat timing , or .200" duration is unlikely. There are other examples, but it would be interesting to see the numbers on say an SE 259 and a Wood TW-8 lobe, both 246" at .053".

Then again, I do admit that a lobe could be symetrical, or assymetrical, so even lobes with the same seat and ,200" duration could be different.

Matt, I'm not about to argue cam design or flow bench findings with you. I still believe that we deserve to have the same level of [perhaps meaningless? LOL] info that car cam companies publish. 


Thank you all.
Dave

[MCE]

Even with more data points in the cam description it still won't tell the average punter bugga all, horses for courses so choose wisely or ask the right people.

Exactly.

Most people wouldn't have a clue what they're looking at even if they did have all the
data points. I've been doing this chit over 45 years, and i'm still learning (thats what keeps my interest)

The only way to really know "what your're buying" is ask the right people, then stick them in the motor
and dyno it. (you can spend weeks/months/years hunting for that elusive couple extra HP/TQ)

The other alternative is, generate the lobe profile (cam pro), load that into the simulator and see what
you get. At the end of the day, you'll have to dyno the real thing or run it down the track like Kirby does.

[HD Street Performance]

Dave, you are right. There is a void in the information supplied. Being as many are made by Andrews and the buyers that get their name and part number attached to them are not experienced in the technical aspects a lot of the grinds (lobe profiles) have similar ramps and intensity or in some cases identical other than a LC or a lift number changed a little.  Others grinding them are CompCams (and Lunati) and S&S. There are some small specialty houses as well. None that I am aware of provide the data like the car guys get. As crude as it may seem you can place them between centers and use a degree wheel and dial indicator, rig up a deal to turn them at 1/2 CS speed. Better than nothing if you don't own a cam doctor. The cam doctor will get you more accurate data but not sure if you can get the true LC angles. I don't own one. I just use empirical data, results from builds using my heads, Dynomation, and Pipemax.

[MCE]

Thank you, Jerry. You are correct. Example, 252* is a popular intake duration. The chance of every 252* lobe having the same seat timing , or .200" duration is unlikely. There are other examples, but it would be interesting to see the numbers on say an SE 259 and a Wood TW-8 lobe, both 246" at .053".

Then again, I do admit that a lobe could be symetrical, or assymetrical, so even lobes with the same seat and ,200" duration could be different.

Matt, I'm not about to argue cam design or flow bench findings with you. I still believe that we deserve to have the same level of [perhaps meaningless? LOL] info that car cam companies publish. 


Thank you all.
Dave

Wanting knowledge is is great. If you really want to understand this stuff, I suggest getting a simulator
program and start playing around with it. You won't get any meaningful information from the cam maker
(other than dyno results from people that have tested) You need the Cam Pro data, they WON'T give that
out, so why bother? Get a Cam Pro and generate the files if you want that stuff, that's the only other way.

[MCE]

This is what I use:
http://performancetrends.com/cam_test_stand.htm

[Nocvo]

By average punter I ment mugs like me not you blokes who live and breathe this stuff, I understand what Dave is saying as well, after looking at Matt's link to his analyser I see there could be a little inclusion on the box that may be helpful to some, by that I mean a little wave gragh that shows intake and exhaust lift over duration, but as Matt said that is not information the cam owner wants to share.

[MCE]

The average 'user' really doesn't need (or care) to know some of this stuff. They only care about the end result.
If you fall into that camp, just find someone that does know it and leave it to them.

[Nocvo]

The average 'user' really doesn't need (or care) to know some of this stuff. They only care about the end result.
If you fall into that camp, just find someone that does know it and leave it to them.

I like to know the why of things at times, well enough to make some sense of it, thanks for sharing your knowledge, I won't be running out to make my own cam design but I do find cam topics interesting.

[TIMINATOR]

Dave: I feel your pain! All of the HD cam companies could, but don't choose to provide the info that almost all of the car cam companies do. I have never gotten a straight answer from any of the companies that don't provide much (or any) advertised info either. We do not buy any cams from those companies, ever!
The cam "advertising wars" were heating up in the late 50s, so Ed Iskenderian (Isky Cams) came up with the .050 lift/ duration advertising figure back in the early 1960s (Yep, I'm old!) to "level the playing field", he figured that meaningful port flow was actually happening at .050" and that figure would provide more accurate duration info to the consumer. Crane Cams owner Harvey Crane, in the 70s, coined the term "intensity" to describe ramp rate differences from .050" to .200" so "joe average" could get an idea how "rampy" (therefore having more "area under the curve") a cam is in relation to another cam.
Lift and duration only are but a small bit of info you actually need to select the proper cam for your engine. Lobe separation and advance are just as important, and not usually stated, but can be easily calculated if seat timing is provided.  Competition Cams is one of the few companies that publish all lobe; lift/duration/shape/characteristics in one book. Crane tried that for one year in about 2005 and then hasn't done it since.
We Cam Dr. analyze most of the cams that come through here (automotive and HD), and have for 25+ years, thats why we use the cam companies that we do and leave the junk and "companies with something to hide" to the uncaring. We also don't select cams by "how they sound in another bike." Harsh, but true.  TIMINATOR

[TIMINATOR]

I also agree with Dave that two cams with the same .053" duration can easily be 6 to 8 degrees different at .006" lift. You only need to compare the same old, same old "house brand" (40+ year old automotive grinds) cams to more modern Comp Cams grinds to see that. I have one of those in the shop that I refused to install for a customer's engine.
If both cams have the same .050/.053 duration, but different .006" advertised durations, the one with the longer advertised duration will have poorer idle vacuum and idle quality, and higher idle emissions too, than the modern grind. You don't even need a Cam Dr. for that comparison, its all on the cam cards!    TIMINATOR