Actually CMotorsports has their own lobes and can grind cams "In House" It is a decent amount more expensive than a $250 off the shelf cam though.

 

First off......

One thing that understanding what complex physics goes into proper cam design gives you is the realization that camshaft lobe design is about the most complex engineering in a motor.

BTW It's not like we are the only guys in the country who spec out and supply custom camshafts to people. Like head porters there are a number of us out there.

I personally ONLY work with Comp Cams on my camshafts, it's a long hard fight for anyone to convince me otherwise.

Joe works with Crane, neither one of us plan or would ever want to GRIND our own cams. The actual machining process is very complex and for it to be properly done is like any other skill learned over time. I know that the there is one guy at Comp who grinds the high end NASCAR camshafts and he has a few people he trains to learn this trait. I'm pretty sure that most other places are lucky to have one guy like this let alone a whole place full of them. My personal choice of Comp Cams is partially due to their machine work, as of right now they are the only company in the country (I'm guessing they will not be alone soon) to have CNC Okuma cam grinders. These cam grinders can make camshafts so accurate that I can specifiy camshaft lobes and their LSA down to .1 of a degree. As far as I know I've never seen another company be able to grind with that accuracy.

That brings me to this, other companies are running in second place when it comes to the actual machining of the cams IMHO. Not just my opinion but most NASCAR teams agree with me on that, that's why the other cam GRINDERS out there are not winning the 125's and 500 at Daytona this weekend.

The second part of camshafts is the lobe design. The propritary sowfare and expertise that Comp and Crane have over other companies is emense. Spintron machines to watch valve and valvetrain motion are a big addition. I personally think that Comp has the edge here, but that's my opinion and I'm sure Joe's is that he thinks it's Crane. I use a wider variety of lobes than he probably does so that's part of my reasoning, the other is that I think the most talented guy in the country works for Comp. BTW when I say variety of lobes I mean SR, HR, Solid Flat, Hyd Flat, different RPM levels etc.... Comp has almost 200 Hyd Roller lobes alone! All of them have their own use and purpose.

Different designs come from different companies. Propitary lobes from a company just come with a price tag, from my experience a change of a few degrees here and there is not as big of an impact as having certain valve events happen when you want them too. The ramps, flanks, and different parts of the lobe profile also have a big part in cam selection. Joe and I both look at that I'm sure. I have one hell of a selection at Comp so that keeps me happy and keeps me away from having "custom" lobes made.

Part three to a camshaft design is what Joe and I do. I base my camshaft specs off of the car and motor specs. HP and TQ in the operating RPM range are what I try to achive, I don't have control of your driving skills, car tuning ability and suspension setup, my job is to focus on the motor, so that's what I do. A fast car is more than just a strong motor, but it has a good deal to do with it.

Part four is making sure the rest of the hardware goes with the camshaft. That is to me as important as the right camshaft.

Hey I don't design the connecting rods in my motors, nor do I machine the pistons either. There are parts manufactures and there are engine builders. They give us quality parts and we build them into quality engines. If what we do is so trivial then go build the next motor to win the Daytona 500 or the Summer Nats Pro Stock race.

Machining in itself is an art, plain and simple. I've had the luxury this last few weeks to inspect and tear down motors machined by other shops and have been very unimpressed with what I have seen. We are talking about specs that are off .005 or more in certain places. That doesn't sound like much but once your motor goes boom you will care. One such motor needed the whole engine block scraped because so many things were off. The places the motors came from and what was off suprised me enough. I'll keep the names to myself, but it's likely that you have heard of them. That is why forums scare me to a degree, you never know who's "experience" you are getting and what makes them qualified to make that choice. I recomend parts I am comfortable with and I have Comp Cams on the top of that list. they might lack in the cam selection arena but they make up for it in making high quality parts, as a supplier that's what I am looking for them to do.

Picking a camshaft is just like any other spec we (engine builders) put into a motor. We are just being hired to assist with the selection process and supply the camshaft to racers who choose to use our services.

Jon,

BTW a cam blank starts off as a billet or cast core (cast for flat tappet camshafts or for factory replacements like a HR cam) The core is premachined to a determined shape so it can be heat treated and then is left on the shelf so the cam can be ground to it's final spec and shape. The heat treating leaves a case hardness on the camshaft, that case is only so thick so you can't just grind anything on any blank because you might break thru that case hardness, which is a bad idea if you want the motor to live.

From what I know some places do grind their own stuf, yep they actually do the machining of the camshaft, not me boss. Our family bussiness is centerless grinding (and CNC machining), like that is done on a crankshaft, the cam grinding process is not a easy feat to handle. Say what you will but if you grew up in that environment then you would understand that, it's a old Economic Law that Adam Smith came up with a long long time ago, it's not just me making things up. One reason why I am VERY skeptical of ANY place that says they do their own is because I've seen what it takes to do machine a camshaft CORRECTLY. Would you have your engine builder make your pistons for you? Not me. IMHO the ignorance or ego to think that you can grind your own camshaft is a scary proposition.

If Joe's lobes are like that then that's a great way to keep valve float and lifter pump up down on a HR setup. The right lobe selection and component selction can do the same thing. Different cam lobes do different things, sometimes a east closing is good, sometimes it's not.

As I said track numbers are track numbers, there is a lot between the camshaft and the pavement to me and most of it has a big impact on the performance of the car.

I'm not defending what I do, the people who know that it's worth while come to guys like Joe and I. They are also the ones who put fast cars out there. If they share their specs then there are the copycats who copy them and end up having the same setup but it's usually not as fast, been there and seen guys do it time and time again. Me I'd rather put my nuts on a table and beat them with a hammer. A good quote about this is from Paul Van Valkenburgh "The engineer or mechanic who blindly copies a faster car, or who is so set in their ways that they refuse to experiment, will just waste everyone's time." BTW Paul Van Valkenburgh is a Engineer who writes for Racecar Engineering. Not your standard car mag that you pick up on a trip to the grocery store, he has also wrote some pretty informative books on racing. Try a google serch on him.

So if you want a fast car you can come to us or do it on your own. Personally I've looked at my prices and others and if I chose to put the same parts on my car I could get them for about the same price someplace else, then again it's the right parts to make the power and reliabilty that make the difference, belive me a "budget" cam kit is lacking someplace from the optimal setup. I build motors and give out my advice in the frame of mind that if I was in your position that's what I would do if I was you. Sometimes that might mean you should spend a few bucks here and there, hey you never get something you don't pay for.

Bret

 

Whoa, explain that one. Those are 14 second cars stock.

 

OMG Bret, thats the most Ive read in one sitting since like Freshman year in HS!

Anyway, I guess I had either a little misinfo or just not enough info on some things. I was going off of what was told to me by LE, just about Joe.

Let me get it straight. When you spec CC a cam, you spec them every little detail, IVO, IVC, EVO, EVC times, centerlines, LSA, etc... Now do they grind that into a cam core with a bunch of circular lobes, or are they already shaped like a XE cam, and they just grind it to the specs. If so, what would make a totally custom cam, designing the lobe and everything, better than that process..if it does?

When LE was explaining it to me, it sounded like CCs cams are just cast cores, and one of the options from Joe was a steel billet (the ultimate cam persay). What would he have been speaking of that it is different than a custom cam from CC?

Im sure I have a few other curiositys about the process, but ill start with that.

 

Ok I start off shooting for a certain IVC and then use lobes to get me where I want to go. Different lobes for different things, maybe it's a Ford HR lobe, or a Magnum lobe or XE lobe depends on what I want the cam to do. Once you get into SR stuff you find more options on ramps, aggressiveness of the lobes, lobe shape and design, RPM range, lift, exhaust vs intake profiles etc.... The lobe design process is EXTREMELY complicated, you get into the 3rd, 4th and 5th derivative of velocity (2nd being acceleration, 3rd being jerk) I don't know about you but I don't really want to get into doing that math just for every camshaft a guy wants. On top of that you have to replicate that theoretical lobe, then throw it in a spintron machine and see if it's going to work or not.

So in essence a totally custom camshaft would only be doable on a econmic level of a NASCAR team. In fact they have their own spintrons to make sure they get the rest of their parts in the system right. On a side note to that, Greg Anderson the guy who basically ran away from the Pro Stock field. Well he used to work with the guys he runs against and on top of that hired some NASCAR boys away from Gibbs and walla he is all the sudden faster than anyone else. That's the big key here, they have the tools and connections to get that stuff done. I've heard that guys with pockets like Roushe can get a lobe designed, a cam ground and out the door in a day. I'm doubting that most guys have that kind of money in their cylinder heads around here.

Well that is a grosely misinformed statment. There are actually a few guys here who have Billet cores from me and they were ground at Comp. I wouldn't say that the "ultimate" core is a billet, maybe a billet with the right extra tricks done to it. Not saying what they are, but at least one guy in this thread alone knows.

A billet camshaft is a stiffer camshaft and it will twist and deflect less than a cast core will. I use billet camshafts when the spring pressures dictate it. Any race solid roller needs it, some solid rollers do not need it while some HR cams should have it. Basically the billet core is going to produce more accurate valve events.

A cast core is not a bad thing, for something like a stock head setup it's a perfect thing to do. $40 less on top of that.

A Comp billet core from me starts at $300, with more design work, more cam options that can climb, but it's only needed in a true race motor setup. It could approach $600 without extra design time factored into that, I'm pretty sure that 99% of the cats around here don't need a $600 camshaft.

Now here is the funny thing... Comp/Crane/Lunati etc... buy their cam blanks. Yep they don't even make the cores. So even the big guys can't do it all.

No problem. I'm sure some I can answer and some I can't and some I'm not willing too. lol

Hey thanks for that post on gasket thickness I just had to reference that for a compressed thickness that I forgot. Sometimes the forum is faster than digging thru piles of paper to find something.

Bret

 

Alright, so then technically there is nothing more "custom" about a billet steel cam than a cast cam then, just other added advantages just like cranks, rods, and such huh..?

When you say that Im assuming you mean its not in everyones best interest to buy one, I would assume that for someone looking for every last ounce of power out of some particular setup, whether it be all race, or a stock head casting setup, it could still be worthwhile?

Bastards


Again, Im sure you hear it enough, but maybe not...I know how busy your life probably is and its not worth it to you to be on here expaining things to creatons like us that will die not knowing as much as you have forgotten, but you do it anyway and I think I speak for most that its greatly appreciated. (haha hope my nose didnt get too brown )

Ha, then again maybe it is worth it to you to be on here Im sure theres still a few missing there though, kinda dropped off the list though.. ahwell

Jon

 

Yep about the same.


Nah not really, we are talking about tricks that you would find only in a dyno cell on a certain engine and some things that I haven't figured out how to do on a LT1 yet.

I like explaining things!


Bret

 

thx bret ...it is real nice to see put thie into this .....thx

 

Sorry Rippin I forgot to add what he ran before. Anyway what should have been mentioned was I think he picked up .5 or so with the cam swap from one what he was running before. I don't know all the details but the owner was very happy with his cam as well. Good catch.


I called Comp cams before I started all of this and they mentioned the same cams everyone else runs on the board, the XE's, 305, 306. Didn't seem all to scientific to me, just toss in a cam and hope it works. For some it does and for others it doesn't. It's a crap shoot with off the shelf cams and even with some aftermarket or ported heads. I rolled the dice and lost, thankfully Joe was around just in time to get me out of my poor combination.

Also Tin Shed surfaced as well as Lloyd Elliot to make sure we got well ported heads. I figure it's a good time to be owning and modding an fbody. There's lots of knowledgable people willing to help out right now.


I'm just glad Joe, Bret, Eric and Lloyd are helping those of us that don't know how to correctly design or configure a proper top end or port our own heads. If they didn't do what they do I would still be sitting at 12.95.

 

Well, maybe not all of them. The reason a large cam company buys cores is that to do them economically you need volume...maybe the volume of more than one cam grinder.

Cast cam cores are easier to make than billet cores because you need only machine the journals, nose, and distributor/oilpump drive gear, heat treat it, and finish grind the journals & nose. The general lobe shape is cast in, so that's what the cam grinder finishes. The lobes and journals can be locally surface hardened. A given core can be ground into quite a number of lobe forms. Sure, there needs to be various cores for SBC to cover the wide variety of flat and roller lifter lobes and separations and maybe 4-7 swaps.

A "billet" core is completely machined from a chunk of bar stock, often 8620, a chrome-molybdenum case-hardenable alloy steel. These are usually made on high-end CNC lathes which are able to rough shape the lobes and well as all the other surfaces.

The semi-finished cores are then copper plated which is used for heat treat "masking". The lobe surfaces, journals and nose...any areas that need to be hard on the finished cam have the copper removed to expose the steel. This could be done a number of ways. The whole billet is then case-hardened, or heated to around 1600F in a carbon and maybe nitrogen rich atmosphere for hours. The carbon diffuses into the surface of the non-copper plated areas maybe .040-.060 deep. The copper plating prevents diffusion or "masks" the other surfaces. The hot part is then quenched (cooled rapidly) probably in oil. This hardens the carbon-rich areas above Rc60, but also hardens the "core" or material beneath the hard shell or "case" and all of the copper plated areas to maybe Rc 45-50, which makes it extremely tough, but not brittle like the Rc60 surface on the wear areas. You get the best of both; wear resistance and extreme strength and toughness. There is at least one final tempering or heating to 350-500F (depending on the case and core hardnesses desired) to remove stresses and fine tune the hardness.

More than likely, the heat treated core then needs to be straightened before final grinding of all the finished surfaces EXCEPT the lopes. This is the core that the cam grinder buys from a "cam core" maker. Again, there is economy in volume, so, considering all the machinery and heat treating equipment needed, most cam grinders would rather spend their capital on equipment to design, test and finish grind the lobes, which is really where the expertise comes in.

Some cam companies do manufacture their own cores. My guess is even they buy the castings from a foundry. Very few folks cast their own cores.

Like an engine builder buys the basic parts from high-quallity suppliers and finishes them or assembles them in a combination he choses, most cam companies do the lobes on high-quality semi-finished cores made to their specifications.

My machining business doesn't make cam cores, but we do make "blanks" for high-end gear manufacturers who put the teeth on them (their specialty), and sell them to folks who make high-end race components. The reason this happens is that we have the right equipment and facilities to make the blank but we don't know much about making gear teeth. This is the most economical way to get a high quality part unless the volume needed will keep your machinery busy all the time. Same thing for cam cores.

 

Good info guys

 

some people want/need a custom can and others never will.

the only way to change peoples minds if their car is running fine with a shelf cam is for them to geta custom cam and they have no reason to in theirminds.

I feel that a custom cam can improve over everyones shelf cams.

Bret's mile long post says alot about people trying to pick their own cams. If they can't even understand what he is saying, they probably are not gonna be able to pick a cam as good as him.

If you tell your cam grinder what you want, he will factor in all of these things and get you more from the cam.

More HP, More TQ, More low end, More mid range, More top end, More reliability, wider power band, etc. etc. If you have a GOOD catalog cam, the cam grinder might omnly be able to improve on a few of these things but for the most part, he can improve on most of these and with smaller specs than you think.

Bret, Joe, Combination Motorsports, etc. can ALL do this......just tell them what you want and are willing to sacrifice and they can get it for you. It might not be $249.99 like most of the XE cams but they can get it for you.

Lloyd

NightTrain66@msn.com

 

Jon, I didnt want to quote your post since it was huge.

Anyway, how much do you think a cast cam would flex under higher (6-7000 range) rpm operation assuming heavier than normal springs, in the 400lb open range. Im sure you dont know the exact numbers on how much load is on it, but I guess make a comparison between how much potential for flex a cast cam has compared to a billet steel cam, or should I call it chromemoly since that sounds cooler.

Seems to me that any slight flex in a cam can mean big (relatively speaking) losses in power. Assuming however much flex you multiply by 1.6 at the valve. Even 2 tenths of an inch of flex, which seems possible i guess comes out over three tenths at the valve. Not to mention how the valve timing would probably get thrown off as well if it flexes in a twisting manner.

All just hypothetical questions, I have no proof behind my theories, just wondering.

Bret, this will sound dumb, but could you recommend any books on cam designing, doesnt matter how it is written, ill figure it out, I want to start learning how.

Jon

 

Just thought Id post this up. Crane does make their own cores, they still buy the metal from a foundry, but everyone does that. Not flamin anybody, just thought it might be interesting info.

 

Maybe the biggest problem with camshaft movement isn't bending but torsional winding and unwinding. Power prolduction is probably screwed up more because of this. Additionally rollers impose different loads on cam lobes than do flat tappets. FWIW, if a cam "bends" between the journals in operation it is probably measured in .0001s or .001

The other bits in the valvetrain , namely pushrods, rocker arms and lifters (in that order) are MUCH less stiff than a cam. In a valvetrain, stiffness or the ability to resist deformation with load is Job One. I don't think looking a "cam flex" or bending is where you want to go.

I'm sure folks in the business try to calculate all of these things, but I believe they get their best results from actual testing with a Spintron.

The botom line is EVERYTHING in nature is a spring; some are just stiffer than others.