Designing Camshafts

mke said:

OHSCrifle said:

Seems like a long shot but not impossible. If an old cam is the right length and generally bigger, why couldn't it be re-ground to a smaller physical shape? It's just a piece of metal, and getting something from a junk yard and whittling away on a mill or lathe using your own labor seems like the definition of Grassroots.  

In theory sure, but the odds of having metal to cut everywhere you need the metal is pretty much 0%. You need 2.5-3" OD depending on the engine the cam is going into.  I used 8620 rods but if you had your heart set on iron you could by iron rods instead of steel and succeed.   Making functional engine parts is pretty hard......

mke you are right. It wouldn't be easy.  The stock cams aren't exotic  and as the picture shows very big. I'm accepting the practical limits dictated  by the engine. 
   Lift over .500 at the valve can't be achieved without complete re-engineering.  
    Besides what you've achieved  with your Ferrari was already tried by the  Jaguar factory.  They put a 4 valve set of heads on the V12  and didn't find enough improvement on the race track to go further.  The added weight on top of the engine offset any power gains. 
   On the Jaguar V12 it's relatively easy to do. The Six cylinder 4 valve head was designed after the V12  so it practically bolts on.  ( well one side you have to turn it around, put the cam drives on the other end ) 

Paul_VR6 (Forum Supporter) said:

Some days I think frenchy must be some 13yo misreading his grandfather's journal. But kids these days have better things to do. 
 

that being said you (well not me, but one with the right tooling) can make a cam from a billet, without a core

 Thank you.  
  One correction though?  I've got a 16 year old granddaughter.  ;-) 

A 4V head has about 20% more valve perimeter than a 2v head.  That means a 4v head exposes 20% more flow area at any given lift until the perimeter x lift exceeds the port throat area.  This allows the 4V engine to want less duration and lift in the cams and generally beat up the valve train a whole lot less at any given hp.  Which will make more hp depends on what is limiting max rpm....if its valve train then the 4V wins, if its stroke and piston speed then they should have similar peaks.

A 2 cam 6 or 4 cam 12 means LSA we keep talking about can be set during tuning vs by the cam grinder so its easier/cheaper to do development work on but there is no fundamental advantage of 4 cam, other than again lighter valve train not beating itself apart quite are fast. 

Those are just physical limit type items.  1 cylinder or 12 or 38cylinders doesn't impact really anything on cam selection, porting choices, header sizing....a cylinder is a cylinder and doesn't much care what lives next door.  Best to separate engine design from cam design.

mke said:

Paul_VR6 (Forum Supporter) said:

that being said you (well not me, but one with the right tooling) can make a cam from a billet, without a core

sure, I designed and got a buddy to make me 48 lobes worth

But make a cam for 1 engine from a cam from another engine is a whole different thing.  Before heading down this path I tried to talk a couple cam grinders into re-timing my TR (testarossa) cams to match the 400i firing order and was told multiple times it can't be done....and that was just re-timing a few lobes, not taking a cam from 1 engine and putting it in a whole different engine.  I never want to say something is impossible but it is wat easier to scare from scratch than to do that.

What you've done is really impressive. 
   Actually pretty. 
  You are right making a cam from a totally different engine work would be a massively difficult task. 
    You'd have to have enough core to leave you with about a 2 inch solid rod, locate the bearings and lobes ( I'd only need 24  lobes) then have those lobes ground into the profile you want. 
  I'd have to talk to the cam grinder to find out if cutting off the back side of the lobe  would help or hinder him. You could do it on a vertical mill  easily enough. ( oops,  I should have said straight forward  because nothing about this would be easy. Just doable. 

frenchyd said:

In reply to Mr_Asa :

Sure. Just look up Black Jack Spl. These are the trophy's  that really mean something to me.   Most of the rest I didn't bother collecting or gave to corner workers. 
  If you look at my Name you'll see me on the pole at Navy North Island San Diego. Next to me is a Ferrari Testa Rossa. Behind him is the 1956 LeMans winning Jaguar D type behind him is another Ferrari Testa Rossa 

Behind me is the only 1957 Corvette SS made by Duntov.    Cars in that field were probably worth 200 million dollars  and the trophy on the top shelf.  The Crystal glass bowl says First in class. 
      There is a video of me Racing against Sir Sterling Moss  in the Bahama's  during speed week.   Watch it through to the end.  That's me getting up on the podium  to finish second to him.  That's the trophy on the second shelf. 
 

Have fun checking me out. I sure had fun racing. 
       

Fairly sure you got the wrong message from that post, but whatever. 

Have fun stormin tha castle.

frenchyd said:

What you've done is really impressive. 
   Actually pretty. 
  You are right making a cam from a totally different engine work would be a massively difficult task. 

I said I believe it is impossible, that is what a 0% chance of working means....which is quite different from difficult.  The German phase is "This is not possible".

If you want to make a cam, make a cam.  Trying to re-make a cam is a dead end and there is no reason in the world to try.  Just take the cams you have and send them to Web or Eglin or similar and they will add enough weld to make whatever you want.  Easy peazy....other than they will ask you all the same questions I asked you about the what exactly you are building and won't start until you give them real answers in the form of numbers....just like I asked you for before giving up.

OHSCrifle said:

Seems like a long shot but not impossible. If an old cam is the right length and generally bigger, why couldn't it be re-ground to a smaller physical shape? It's just a piece of metal, and getting something from a junk yard and whittling away on a mill or lathe using your own labor seems like the definition of Grassroots. 

Not trying to argue with you but IMHO Grassroots isn't going all Don Quixote against windmills. In this case I think Grassroots is maybe hand making copper head gaskets so that the boost can be cranked up past 20. Still hand making something to solve a problem. Most likely gains more horsepower than a cam and a lot less time spent that could be used on other things.

Of course ignore all that if Sleepyhead makes an offhand comment about how cool it would be to have a hand built cam.

mke said:

A 4V head has about 20% more valve perimeter than a 2v head.  That means a 4v head exposes 20% more flow area at any given lift until the perimeter x lift exceeds the port throat area.  This allows the 4V engine to want less duration and lift in the cams and generally beat up the valve train a whole lot less at any given hp.  Which will make more hp depends on what is limiting max rpm....if its valve train then the 4V wins, if its stroke and piston speed then they should have similar peaks.

A 2 cam 6 or 4 cam 12 means LSA we keep talking about can be set during tuning vs by the cam grinder so its easier/cheaper to do development work on but there is no fundamental advantage of 4 cam, other than again lighter valve train not beating itself apart quite are fast. 

Those are just physical limit type items.  1 cylinder or 12 or 38cylinders doesn't impact really anything on cam selection, porting choices, header sizing....a cylinder is a cylinder and doesn't much care what lives next door.  Best to separate engine design from cam design.

A cylinder is not just a cylinder. It's a compromise of dozens of factors.  If they were we'd all be driving 5000cc single cylinders for simplicity's sake. 
  There are synergies and compromises that decide things.  
      So it does matter if it's a six, 8 or 12 while it would be interesting discussing the Ferrari points with you versus the Jaguar points. 
 I'm far more interested in Enzo Ferrari, how he came from the Devastation   of WW2. To building race cars again. 
  Sir Lyons did OK during the war and was even able to design the engine that was in production until 1987  42 years!  
   While Enzo produced probably 42  different engines  in  The same time frame. 

frenchyd said:

A cylinder is not just a cylinder. 

I can only point the way, I can not make you learn....but nothing you posted is true, engines just don't work the way.

Frenchy,

You're older than most of us here, and life has apparently been very good to you.  You have had rare opportunity and financial capability to do far more than I, or maybe most of us, ever will.  Nobody here is trying to take that away from you.  So I offer the following with all due respect:

Anything you are involved with here seems to self-destruct.

Why is that?

1) Your posts are disorganized and sometimes difficult to read.  You ramble, you regurgitate, you reminisce.  You talk in circles and spirals and occasionally boast of your success.  You tell us what you want to do.  But you most certainly do not make your purpose clearly understood.
Result: It is hard to discern whether you are asking for help, or looking for validation, or simply waving the flag for the Jaguar V12.

2) You tend to issue the same statements, the same (often debatable) facts and figures, the same plans, the same anecdotes, time and time again.  You've been posting the same comments about the Jaguar V12, including now-deleted posts under your old screen name of "mguar", for something like ten years now.
Result: It's hard to pick the new content from the old.  That makes it hard to know what to pay attention to and what to dismiss, and difficult to respond in a productive manner.

3) You seem to butt heads with others as a matter of course.  When you ask a question, you disagree with the answers others provide.  When your ideas are dismissed as impractical, or as patently incorrect from an engineering standpoint - and, let's be frank, some of your ideas are way outside of accepted practice - you dig your heels in and defend them rather than consider that someone may know something that you don't.
Result: You come off as unwilling to listen to others.  People who are otherwise willing to help you achieve your goals become discouraged and begin to lose interest. 

I hope you understand that nobody here is interested in disparaging the Jaguar V12.  Nobody here is rooting against an XJ-S GRM Challenge car.  Nobody here is rooting against your success with either the Jaguar V12 or the competitive entry of same as a Challenge car, nor any other form of success you might achieve.  But it is no fun helping someone who refuses to be helped.

One final thought.  Nobody knows everything, but most of us here can offer something.  When someone offers you an opinion, it is natural and reasonable to ask for an explanation.  It may be something that they can explain - but if you need any more than a brief overview, that is up to you.  That person is under no obligation to write you a book on how and why they reached that opinion.  There are many fine and well-respected books available on the topics at hand.  They make good reading.

With that, I will take my leave and wish you luck.

Stampie said:

OHSCrifle said:

Seems like a long shot but not impossible. If an old cam is the right length and generally bigger, why couldn't it be re-ground to a smaller physical shape? It's just a piece of metal, and getting something from a junk yard and whittling away on a mill or lathe using your own labor seems like the definition of Grassroots. 

Not trying to argue with you but IMHO Grassroots isn't going all Don Quixote against windmills. In this case I think Grassroots is maybe hand making copper head gaskets so that the boost can be cranked up past 20. Still hand making something to solve a problem. Most likely gains more horsepower than a cam and a lot less time spent that could be used on other things.

Of course ignore all that if Sleepyhead makes an offhand comment about how cool it would be to have a hand built cam.

You are probably correct about all of that.   I do some things the hard way  because it doesn't cost anything. That's not because of the challenge but just the way I am.  
  Other things I do  the hard  way because buying it is just too silly for the gains made.   
 Finally some things are done by hand because they aren't available. 
 On the other hand I'll spend good money for things I want.  Or the cost is in line.   Sometimes I'll even spend more money then I have too.  Example? The fender flairs.  I'll make molds off the ones I bought and  make my own set of flairs.  By Challenge rules only the money I spend on parts that go on the car count. 
 ( but actually it's smart  to have body parts spares because accidents do happen sometimes in a race) 

DarkMonohue said:

Frenchy,

You're older than most of us here, and life has apparently been very good to you.  You have had rare opportunity and financial capability to do far more than I, or maybe most of us, ever will.  Nobody here is trying to take that away from you.  So I offer the following with all due respect:

Anything you are involved with here seems to self-destruct.

Why is that?

1) Your posts are disorganized and sometimes difficult to read.  You ramble, you regurgitate, you reminisce.  You talk in circles and spirals and occasionally boast of your success.  You tell us what you want to do.  But you most certainly do not make your purpose clearly understood.
Result: It is hard to discern whether you are asking for help, or looking for validation, or simply waving the flag for the Jaguar V12.

2) You tend to issue the same statements, the same (often debatable) facts and figures, the same plans, the same anecdotes, time and time again.  You've been posting the same comments about the Jaguar V12, including now-deleted posts under your old screen name of "mguar", for something like ten years now.
Result: It's hard to pick the new content from the old.  That makes it hard to know what to pay attention to and what to dismiss, and difficult to respond in a productive manner.

3) You seem to butt heads with others as a matter of course.  When you ask a question, you disagree with the answers others provide.  When your ideas are dismissed as impractical, or as patently incorrect from an engineering standpoint - and, let's be frank, some of your ideas are way outside of accepted practice - you dig your heels in and defend them rather than consider that someone may know something that you don't.
Result: You come off as unwilling to listen to others.  People who are otherwise willing to help you achieve your goals become discouraged and begin to lose interest. 

 

I hope you understand that nobody here is interested in disparaging the Jaguar V12.  Nobody here is rooting against an XJ-S GRM Challenge car.  Nobody here is rooting against your success with either the Jaguar V12 or the competitive entry of same as a Challenge car, nor any other form of success you might achieve.  But it is no fun helping someone who refuses to be helped.

One final thought.  Nobody knows everything, but most of us here can offer something.  When someone offers you an opinion, it is natural and reasonable to ask for an explanation.  It may be something that they can explain - but if you need any more than a brief overview, that is up to you.  That person is under no obligation to write you a book on how and why they reached that opinion.  There are many fine and well-respected books available on the topics at hand.  They make good reading.

With that, I will take my leave and wish you luck.

That is valid. However I do feel that often I'm answering one question or debating one subject with someone and others join in based on misunderstood points.  So I go back and repeat things trying to explain in a different way.   
     Take the point of this whole thing. Camshafts. 
 30 years ago I bought my last set of cams.  I believe that in the last 30 years progress has been made in camshafts.
  If I'm wrong then everyone is owed an apology.  But I don't believe I am.  Do you? 
for example, Those who advocate I research domestic pushrod V8's  when I'm discussing overhead cam engines.  While I'm focused on Jaguar,  Porsche,  Toyota,  Honda, BMW dozens of others are raced with overhead camshafts.  
   I'll take responsibility for confusion.   I should be less polite,  more direct. 
     I've tried to post statements to those who made erroneous statements  But often enough others repeat the same point. 
   For example. Pushrod engines aren't the same as overhead cam engines. Spring tension is much lower, the lobe can be much more abrupt.   Pushrods, rocker arms,  and lifters are far more flexible and heavy than OHC  thus profiles,  lift, duration, etc will vary. 
 

   
     

Hmmm.  Quite a thread- I read all of it and forgot most of it already. This pops to mind: Given your project, Kids These Days would get a couple of big Chinesium Ebay snails, and a couple big dumb cost effective Chinesium inter-coolers, a 4 wire o2, intake temp sensor, exhaust temp sensor, whatever other junkyard sensors, hook it all up to a laptop with whatever tuning freeware or a megasquirt set up, or skip all that and go with some beer and a timing light and spend all their time getting whatever completely OEM engine to an insane power level.  Not grenading is the challenge, making power is stupid easy.  You are worried about camshaft grinds when your stock cams and a decent cheap turbo set up will blow the thing up way before you are wondering how to get another 40 ponies out of it with a unobtanium ethereal perfect grind.  NA perfection is a whole other deal.  

In reply to Shaun :

Hes already got 2 

In reply to Shaun :

 That's the direction I'm looking at right now. At least for the challenge. 
  But once that's over I want to race vintage.  That is when I go back to NA and play by the old rules in Vintage racing. 
   I know that even Vintage Chevy Engines have camshafts updated  recently.  Yet no such updates have taken place for the Jaguar V12. 

In reply to frenchyd :

My understanding of that is roller rockers afford steeper ramp rates and the push rod V8 world has been going in that direction hook line and sinker for quite a while now.  That roller interface changes things a bunch...   I know the architecture is different, and anyway the ('Merican) domestic V8 folks at https://www.speed-talk.com/  know their stuff inside and out.  Allot of very very experienced professional race engine builders there.  Mostly 2 valve, high RPM, lots of valve spring rate, bespoke everything (obviously including cams), very serious engines.  It would not suprise me at all if there is some familiarity with your architecture there. 

In reply to Shaun :

It's just physic's. The greater the mass the more resistance. Then we have the old, " Body in motion  tends to stay in motion until acted upon by outside forces. 
     Grab the roller rocker the push rod and the lifter. Then grab the hollow shell cam follower and little shim. One hand probably is lifting twenty times as much weight as the other if not more. 
      Since all of that has to remain in contact, pthe spring for a rocker arm  is going to be at least twenty multiples of what the spring for the overhead cam engine. Probably more than that.   Then there is the resistance.  

    Overhead cam slides across the cam follower and that's all the resistance. 
  Rocker arm slides across the lifter and across the rocker arm and finally the roller on the tip of the valve stem. 
  Think rollers make a difference! Grab a roller bearing and give it a spin. Notice how quickly it comes to a stop?  
 If rollers really were the answer just put roller bearings on everything. Crank rods etc.
 

I understand NASCAR  has engines that can rev to 10,000 rpm  and Last for two 500 mile races plus practice and qualifying. 
Don't  you don't you think they'd rather have overhead cams? 

frenchyd said:

 If rollers really were the answer just put roller bearings on everything. Crank rods etc.

I'm not sure if you're serious or not.

In reply to Mr_Asa :

It has been unsuccessfully tried many times. 

In reply to frenchyd :

Don't tell Harley, they have roller bearings everywhere in their engines, lifters, rockers, crank and cam bearing.  You can use roller bearings where ever you please, its just expensive.  

Sad  to say I've never worked on a Harley. I wasn't aware of that. 
  If it's better then why don't high end engine builders use it?  Ferrari Aston Martin etc?   Or NASCAR Formula  1 etc?  

In reply to frenchyd :

Better depends on the application.  The design goes back to total loss oil systems and was borrowed from early aircraft.   2 strokes are similar and I saw an F1 bottom end  just spinning when flipped by hand....roller bearings that best I could tell.  The down side is it's expensive to build when the crank has more than 1 throw.

In reply to mke :

I'm advocating you look at cam in block old school V8 stuff because the information actually exists and is abundant.

You probably aren't going to find a lot of people giving you the info you want for a jag v12, hence your post here. If you can, as I've advocated before, copy them and quit thinking about it.

You're here asking about cam basics and since jaguar info doesn't exist, do you know what kind of motors people commonly change cams in and posts results.....old school cam in Block V8s. So you can see what they had, how the cam specs changed and how performance/hp/torque/powerband changed, and use that to, probably poorly, guess at some cam specs, and have a general idea on how things might change.

As MKE said a cylinder is a cylinder (he didn't say an engine is an engine)  which is real similar to what you said "it's just physic's"

Hilarious! That is all. 
 

Opti said:

In reply to mke :

I'm advocating you look at cam in block old school V8 stuff because the information actually exists and is abundant.

You probably aren't going to find a lot of people giving you the info you want for a jag v12, hence your post here. If you can, as I've advocated before, copy them and quit thinking about it.

That is right, either buy a 70s ear cam  or do something new.  I'm sure the 70s cams still work fine so that is not a bad option, open catalog, buy cam. 

For new there is no real reason  to try to find a similar engine to compare to.... all the major cam grinders have and use software that looks at the physics and delivers an excellent answer.  At the limits or high end racing they tweak what the software output but for the rest of us....its going to be an excellent cam. 

Google tells me the jag cam on bucket so its going to be lift limited, but its got quite large valves at 44/37mm to get it to full flow are relatively low lift.  The issue big valves like that cause is they don't like a lot of duration so the cam design effort focuses on ramp angles and maximize valve acceleration.  Numbers in cam catalogs of on cam cards are generally of little value honestly.

But none of this matters here......bolt the turbos on and call it done.