There are four designations that I'm aware of:

1. The lobes are selected from a library of pre-existing profiles, and the designer determines what order of position, LSA, etc. the lobes are to be ground in.

2. The cam designer creates the lobe profiles himself from scratch, and then determines what order of position, LSA, etc. to grind them like in example #1.

3. A pre-existing "off the shelf" cam design is ground with a different LSA.

4. The cam is ground with a different base circle diameter than that of any stock standard or "off the shelf" cam. This can be done in combination with any of the first three designations.


If there are any other methods that anyone can think of, feel free to chime in.

 

Other than clearance for rods, for example, or to convert a lobe from one core size to another why option 4. ?

I'll suggest another possibiity:

The engine designer determines what the engine wants, what is physically possible/practical with the lobe and lifter geometry, and he then designs the rest of the valvetrain around what the engine wants. This may use lobes which already exist, but which may not be in the normal lobe catalog, or it could involve an expensive new lobe design. One of the problems is that the new lobe should be checked for valvetrain stability (Spinton). The rockers, springs, retainers, and pushrods might need to be new or different from what's in the catalogs.

How import is winning? or in more familiar terms, "How fast do you want to go?"

Jon

PS: There is always the option of directly copying another (successful) cam and relabelling it. That's usually the least amount of work for the "cam designer."

 

I think you just answered your own question.

But in all fairness, I'm just dealing with the "how's" here. The "why's" are an entirely different 50-page flame-fest altogether.



Customer: "How would I go about making an LT4 Hotcam work in my 396 stroker project?"
Cam Designer: "Grind it on a smaller base circle to clear the rods."
Cam Designer: "By the way, why would you want to run that cam in that engine?"
Customer: "???"

In any case, if by some tragic series of events that cam still ended up in that engine, it would be a custom by virtue of it simply being on a smaller base circle, no?

 

The characteristics of the cam will change when a lobe designed for one base circle is ground on a smaller or larger core. The effect is usually subtle and I am too hung over to go into it now. Maybe later.

Rich

 

Not On Call last nite, Doc?

Lobes can be "converted" digitally from one core size (base circle) to another with little or no change in lifter motion when using a CNC lobe grinder. This wasn't/isn't so with solid cam masters.

TSATF, the recent 396 LT1's I seen used a "standard" base circle. I guess it depends on the rods the engine builder chooses.

Question: If I have Comp take one of their shelf grinds but label it as the "OSS-1", is it now a custom cam?

Perhaps we should call cams specifically designed for a certain engine/vehicle combination "Engine Specific" rather than just "custom".


Jon

 

Jon: yeah, I was off for a change! And we went to the neighbors (who are now also my son's parents in law) so it was a walking (stumbling) proposition. No need for a designated driver. Instead, I was the designated drinker.

It doesn't surprise that the new ways of making cams can adjust for base circle like that. I was thinking of the mechnical masters. As far as "custom" goes, it can be worth the hundred or so bucks it costs to just have someone who knows wtf they are doing select the cam from the off-the-shelf stuff, to be frank about it. And a slight tweak, such as a couple degrees of advance or a small LSA change produce up to 20hp, under the right circumstances. That's nearly free hp. Many OTS cams have too wide an LSA and not enough lift. There are reasons for that, basically, they are trying to protect customers (and their reputation) from themselves. Example: for a given duration and engine, there is one and only one LSA for max power. A couple degrees too narrow and it really screws it up. There is a little more tolerance for too wide, that's one of the reasons the OTS cams are what they are.

I have been experimenting with cams with my bracket BBC. The current cam may not be optimal, but after a couple of tries, I saw (and this is the God's honest truth) a 100rwhp gain (with track times to back it up) from the original to the current setup. Now, in the interests of honesty and my credibility that switch was from a flat tappet to a roller and as well, the whole valvetrain was replaced. The pistons were cut to allow bigger lift, etc. It was not a simple cam swap and cost over $3,000 including the cost for a couple of cams, etc. But it is common to see 20 or even 30 rwhp gains from a properly specced out cam.

Rich

 

We call it "Knee-Walking Distance" when you party close to home.

You make some very good points above, Rich. Getting the air in and out effectively is the key. To paraphrase Willie Sutton, "That's where the power is."

Sutton's law comes to mind.

Jon

 

That depends.

Is the fitment the same?

Firing order?

Core material grade?

Bearing journal diameter?

Or is Comp Cams only charging me for how it's spec'd?

 

I don't put 'one choosing a lobe' and 'cam designer' in the same sentence.

Do you consider a Pharmacist and a Medical Doctor the same?

 

I bet no one on this board is going to invest the five figure amount needed to have lobes specifically designed for their application. Nor do they need to. We are talking about SBC's here. I am not saying that there is a lobe out there for quite every purpose for these motors, but damn close. It is a matter of picking the right ones for what a given set of needs are, knowing what LSA to grind them on, and knowing what is the correct ICL. That knowledge you can purchse for ~$100-200 and it is well worth it. The other thing that those dollars buy is help choosing the correct supporting components, which is also where many people need help.

Rich

 

For one, it doesn't cost five figures - I have proprietary lobes on my cam, as do a few others on here, designed by guys who have decades of experience and proven performance designing cams. No question it is more money to get the power via R&D vs. taking the sledge hammer route or going huge on duration.

Most “custom cams” are all profit for the “designers” ego (read: lobe selection out of a catalog) as they hawk $170 cast core garbage for $400.

 

I think you are being taken for a ride if you think someone designed a lobe especially for you. But if it makes you happy, that's ok with me. I also don't see why anyone should have to design a lobe for you, if your motor is a gen 1 or gen 2 SBC. As I posted earlier, while there must be something new out there in the way of cam lobe ideas for the SBC, most likely it is only what someone THINKS is new and they just reinvented the wheel.

Rich

 

So, going by your statements, there are no more lobe profiles available by 'design' for a gen I or gen II (like it makes any difference, even if you include gen III), and creating one (whether it is proprietary for me or someone else) would just be "reinventing the wheel"? Do you really believe that?

I'm just curious, but what are your qualifications to opine on camshaft lobe design anyway, specifically on the point that anyone with a propriety lobe had to be "taken for a ride", besides buying a few camshafts for yourself?

 

I think what SS MPSTR is saying is that some places simply pick the nastiest lobes in a readily available catalogue, others work with real racing industry professionals to design cams that work without destroying parts.

I will agree that even if choosing standard lobes out of say Comp's catalogue it is money well spent to pay a few bucks extra to get a professional to help you out. Most guys can't get it even particularly close alone, seen too many cars with something like a 306 cam and stock gears or other such terrible mistakes.

 

Why don't you explain to me how it came about that someone designed and tested a lobe specifically for you. Who did it, how much did they charge? How many hours of Spintron and dyno time was used? Why did you think you needed such a special lobe? What are the results? Are you quite sure someone didn't pick the lobes out of their catalog/library of lobes? Who ground it? What you are saying goes contrary to my experience. Maybe it's exactly as you say. If so, please let me know who did it for you on the cheap. If it worked good, maybe I will be their next customer.

Rich

Edit: most people who are effective designers are going to be paid by the hour at quite a high rate. Dyno time and Spintron time are also expensive. You are not going to get someone to grind you a custom cam, test it, and go through a few iterations until they find a design that accomplishes whatever the goals are for less than thousands. My five figure number was an educated guess. Maybe it's only $5,000? That isn't to say it would be anything exceptional, just that it would work.

It's possible, but I doubt that is really what SS MPSTR has going for him. You can believe it if you want, I don't. Someone finding something new, better than what is already out there, for the SBC is going to be a serious cam designer and I just don't see that unless we have a sponsored racer in our midst.

RK