OldSStroker

For me confusion is often a short trip, Rich. I'm sure many people forget where the .050 applies. Of course we should be concerned with valve motion; the engine is. Hey, I have to keep remembering that cam duration is quoted in crankshaft degrees, and LSA is in cam degrees. So a 224/224 duration cam with 112 LSA actually has lobes 112 degrees wide (measured at the .050 lobe lift point) and they are 112 degrees apart! Whew!

So is a 0 suture 5 times the size of an 00000, or 5 X the strength? or maybe just about 80% stronger? And I thought cam nomenclature was confusing. Just picking. My wife says to use a suture that's approximately the strength of the tissue. Kinda like choosing valve springs.

There is an interesting story (which may or may not be an Urban Legend) that Chevy engineers working on solid lifter racing (oops, "off-road") cams noticed that lifter motion coincided with valve motion by the time .050 lifter rise had occurred. They were through all the ramp area. By using this as a check point, the velocity of the lifter in relation to crank rotation was much higher so it was easier to define this point on the camshaft. Others adopted this and here we are. Might be true.

(Probably should have marked this post OT for off topic. Sorry Fred)

72Demon

Man, you guys are the greatest !!! I have been lurking on this board (without registering) for probably almost 2 years now and the ammount of knowledge on this CamaroZ28 Bulletin board well excedes any other board or information source on the internet ! I thank all of you who take the valuable time out of your daily lives to enlighten us all with the knowledge that you all have acquired over the years ! This has truly got to be the best place on the net and I will forever be learning from it as long as it and all of you are around. Thank you all again !

72Demon

turb0racing

Another thought wouldnt the duration be decreased due to the increased load on the lifter with the 1.6 because of less mechanical advantage. this would ony hapen if hydraulic lifters are used, of course you wouldnt be able to prove this unless you had a cam degreer that works while the engine is runing.

OldSStroker

Or maybe the hydraulic lifter oil is basically incompressible and the metal valve train parts deflect more than the lifter collapses. The valve motion sorta follows the lobe, but not exactly, and sometimes not even close. This is measureable at at almost any rpm.

Another thought is that if we are discussing maybe 1-2 crank degrees, the cam duration number isn't even that accurate. Did you ever see a cam quoted with an odd duration, like 223 degrees? In fact, many lobes don't actually measure within 1-2 degrees of their "design" spec.

72Demon

I dont know if a custom cam counts in what you are talking about OldSStroker, but I just picked up a custom solid roller cam from one of my buddies last night that has the specs of .595/.595 lift (1.6 RR's) and 243/243 duration with a 110* LSA and a 104 IC. Anyway, the cam was custom ground by Chet Herbert Racing (not sure if that is spelled correctly) in Illinois. And this brings me to another question, If most cam's dont measure within their designed specs (Comp Cams, Lunati,Crower, etc.) would a custom ground cam from something other than a major company be any more "accurate" than an "off the shelf" cam ? Just food for thought.......

72Demon

OldSStroker

Sorry.

Maybe I didn't say that correctly.The manufacturing tolerance on producing a cam is probably + or -1 cam degree @ .050 which is +/- 2 crank degrees. We have found cams to be about this accuracy when checked. A custom cam and an off- the-shelf cam should both be within the same manufacturing tolerances. I wasn't trying to say anything negative about cam manufacturing.

IMO, Cam companies generally quote figures in even numbers like 210, 214, 224 mainly for advertising purposes. Does an engine know the difference between a 244 and a 243 cam? Probably not! If they offered 242, 243, 244 and 245 degree cams with lifts proportional to the duration, we'd have folks arguing over whether they should swap out their 242/.593 for a 243/.595, and how much more power should they expect. If you think I'm exaggerating, visit some of the other forums.

A "custom" cam can be a couple of things. It can be existing lobe profile(s) ground at a certain LSA, or, more rarely, it could be an entirely new profile design. That, IMO, is reserved for major racing teams. If a cam is not listed in the cam manufacturer's catalog, and they have to grind one for you it's "custom". Some lobes are not offered in catalog cams, so any cam ground with those lobes is "custom".

A cam company could grind a cam with certain lobes and a certain LSA for an aftermarket retailer who sells it as their "special grind". The same cam with a couple of degrees of LSA or even just a different IC might be a catalog item. Happens all the time. Because the cam manufacturer makes more than one copy at a time for the private labeler, there is a price break, and both the cam company and the private seller can sell you the cam for the same $. Very few tuners (if any in this country) grind their own cams. Some (many?) cam grinders buy cam blanks ready to finish grind from suppliers who have invested millions in equipment to make lots of extremely high quality blanks which a cam grinder couldn't duplicate for anywhere near the same cost. It's economy of scale. Almost nobody makes hydraulic lifters except specialists. It should be that way. Even OEMs either buy lifters outside their corporation or had one division (Detroit Diesel) which supplied everyone.

Cam lobe design is very sophisticated, and good cam manufacturing is very precise. The major cam companies have excellent designers, and computer design software. Chet Herbert is well know (especially among us OFs). I'm not sure what their design capabilities are, but I'm sure their products are high quality. They always were.

Cam grinders use a "master lobe", which is a large, maybe 8 or more inches in diameter, disk which has the exact lift or "rise" every degree and is used on the (non CNC) cam grinding machine to move the cam as it turns and is ground to shape. The large diameter master has the same advantage as a large degree wheel; you can be more accurate. The larger cam companies may have a larger selection of master lobes, especially in the edgy area of agressive, inverted-flank solid and hydraulic rollers.

A good lobe is a good lobe and can be used in many applications. It's matching the lobes and LSA to a specific engine that's important.


My $.02.

72Demon

Ok that makes more sense now. Thanks for the explanation. Boy, there is a lot more to these cams than I ever thought there was !