Roller Cam and Lifters

[tirod]

There are a lot of sidelites in this thread - but $1200 for a roller cam definitely keeps it out of my budget. I'd like to address some of the other stuff -

Flex in a cam is usually not good because bending and twisting cause variations in timing. Cast cams in iron are inherently stiffer because they are high carbon, billet cams are comparatively low carbon and twist more. They just allow easier machining with "connected" lobes to add mass that can prevent twist and bend at lower cost than a whole new casting. It's a volume production price break decision. As a history point, the Chevy small block is the poster child for that and where the market first offered the product. Driving a cam from the front and distributor from the back put a lot of whipsawing in the design - it reacts like a torsion bar springing back and forth in a blown stroker motor. Most street cams don't even begin to have the problem.

Cam overlap was used in the HO motor to eliminate the EGR. The Renix cam had less overlap - power down low, and more emission. The HO cam has power higher up, and allows more reversion to dilute the incoming mixture, reducing temps and preventing nasty stuff forming in the exhaust gas. Pretty cool, a high performance high overlap design is the chosen emission control.

Sometimes it's actually the counterintuitive idea that works better.

[SIXPAK]

On grinding a roller on a cast blank, I have done this knowing beforehand what was going to happen. The cam was in the 250-260 at .050 range and had .630 lift. As expected after approx a year of racing 300 ft sand drags (12 races or so) the nose of the opening ramp and the nose would start to wear. Eventually I turned away from the roller setup. Our rules department make ALL motors carry excess weight for roller cams. Too make a long story short, I could not afford the parts needed to overcome the excess weight for it to be an advantage. In a situation where you would not have to carry added weight(street) the gains would be more noticable.

For example: Solid or Hyd flat tappet cams under .500 lift are 5 points= approx 50 lbs in my class
Hyd cams-------------------------over .500 lift are 15 points=approx 150 lbs
Solid cams -----------------------over .500 lift are 20 points=approx 200 lbs
Solid Roller cams-----------------------ANY lift are 25 points=approx 250 lbs
There is a stipulation for FACTORY Hyd roller cams but I do not recall what the points allowance is for it.

[1bolt]

Interesting stuff how about tool steel? Or chromoly? Is forged billet more flexible than cast iron? Hell what about CNC'ing cast iron billet?

Remember all we're trying to do is form a cam blank, or completely machine one using a less "one off custom" approach... In other words a CNC lathe is potentially way less expensive than Joe the specialty race shop guy.

Sixpac so you ran a normal non roller cam blank custom ground to a roller profile, and ran it knowing that it would wear quickly but slow enough for several beatings. What lifters did you use? And how did the cam look when you pulled it?

I'm wondering if we could just surface harden a normal cam blank... maybe cryotreating it?

Anyone think the idea of getting past the Cam harmonic by using a stiffer cam has any merit? That sure would be a nice selling point... Even if it wasn't a roller cam.

[SIXPAK]

IMO, the billet route is the only and correct way to go. I do not recall the brand of lifters but they are soaking in an oil bath. I still have a worn cam I believe, the opening ramp and the nose are worn. The nose takes the biggest hit with about .010 worn off. I will try to get some pics some time. Building two motors, Very busy.
Just brought this to everyones attention so that others can learn from my past experience.

[Flash]

so not to beat a dead horse but why was it determined that a roller cam has to be extra hard? and How did we arrive at the conclusion that only a full on custom made roller cam blank is the only way to make it happen? I admit to not paying that much attention when this was discussed on the list. But I don't remember anyone bring up these possibilities (probably for good reason). But still worth wondering about...

I'm especially intrigued by the idea of custom machining the cam to spec with a CNC lathe. And forged billet would take care of two things... It would probably be so stiff that the Cam harmonic issues would go away (or at least move up higher in the RPM range) and be hard enough so the roller wouldn't wear prematurely.

Imagine for a moment... If the roller cam had all the selling points of a normal roller cam, but was so stiff and tough, that it also allowed our engines to rev into 7,000 RPM range...

Now THAT would be worth some bucks...

I bet with a few of my junk cams laying around I could model the cam we want in 3D with lobe circles ready for grinding.

I'm glad that this has not become a dead horse

Go thoughts that haven't been researched

Flash

[Flash]

On grinding a roller on a cast blank, I have done this knowing beforehand what was going to happen. The cam was in the 250-260 at .050 range and had .630 lift. As expected after approx a year of racing 300 ft sand drags (12 races or so) the nose of the opening ramp and the nose would start to wear. Eventually I turned away from the roller setup. Our rules department make ALL motors carry excess weight for roller cams. Too make a long story short, I could not afford the parts needed to overcome the excess weight for it to be an advantage. In a situation where you would not have to carry added weight(street) the gains would be more noticable.

For example: Solid or Hyd flat tappet cams under .500 lift are 5 points= approx 50 lbs in my class
Hyd cams-------------------------over .500 lift are 15 points=approx 150 lbs
Solid cams -----------------------over .500 lift are 20 points=approx 200 lbs
Solid Roller cams-----------------------ANY lift are 25 points=approx 250 lbs
There is a stipulation for FACTORY Hyd roller cams but I do not recall what the points allowance is for it.

I'm pretty sure but trying to make it clear
this cam was a stock cast cam that you ground into a .630 lift? what vehicle was this done too

If it was not the stock cam what cam material was it made from?

Heres a question for every body...........What cam material is the stock automotive Hyd Roller cams made of??????????

It would be nice to have a roller cam made on the "cheap"..........even if it only lasted 6 mounts, just to get some real ### on a roller cam, and a tru test of the roller lifters!!!

Flash

[Flash]

Interesting stuff how about tool steel? Or chromoly? Is forged billet more flexible than cast iron? Hell what about CNC'ing cast iron billet?

Remember all we're trying to do is form a cam blank, or completely machine one using a less "one off custom" approach... In other words a CNC lathe is potentially way less expensive than Joe the specialty race shop guy.

Sixpac so you ran a normal non roller cam blank custom ground to a roller profile, and ran it knowing that it would wear quickly but slow enough for several beatings. What lifters did you use? And how did the cam look when you pulled it?

I'm wondering if we could just surface harden a normal cam blank... maybe cryotreating it?

Anyone think the idea of getting past the Cam harmonic by using a stiffer cam has any merit? That sure would be a nice selling point... Even if it wasn't a roller cam.

Flash

I thing thats a grate thought.........And not trying to down play the thought at all! But, isn't it the chain the brakes from the cam harmonics, not the cam?

[SIXPAK]

Flash, The cam that was used came from REED cams. I believe that it was a normal blank that they would use for any hyd or solid cam. The cam was used for a sand drag car.

[1bolt]

I thing thats a grate thought.........And not trying to down play the thought at all! But, isn't it the chain the brakes from the cam harmonics, not the cam?

Feel free to correct me if any of my assumptions are wrong:

The cam creates the harmonic in the first place, by flexing... Just like a guitar string creates a harmonic (which put very simply is a vibration) twanging back and forth; vibrating.

A stiffer cam doesn't vibrate the same, it doesn't flex as much and just guessing but if it was significantly stiffer it would raise the frequency of the vibration (harmonic) higher which means smaller tighter vibrations. Also If you changed the length of the cam, or the amount of tension on it you can change the "sound" (vibration) it would make just like with a string. But making it stiffer and/or more dense will also have the same effect...

Timing chains of all varietys regularly make seven or eight thousand RPM. If I understand the cam harmonic correctly. The chain breaks because the the cam flexes torsionally somewhere past 5000 RPM which flexes the chain the same way...(back and forth) in other words it's fighting between the crank sprocket and the cam sproket. and the chain looses.

Don't even need a roller cam... you could riffle drill a normal cam and press a stainless steel dowl into it... SS is harder and stiffer than steel or iron.

[John]

That harmonic will on the middle of the cam spit the distributor shaft up out of it's mounts, yes it breaks the timing chain in front and can also do other physical damage, have also played stringed instruments all my life, cat gut, silk, or steel strings all make middle c at the same frequency of vibration, and 5600 rpm establishes that set point (or so to speak middle c) for our motor. We are beyond the necessary strength of the camshaft materials. Don't kid yourself, it is about controlling the vibrations.
John

[1bolt]

That harmonic will on the middle of the cam spit the distributor shaft up out of it's mounts, yes it breaks the timing chain in front and can also do other physical damage, have also played stringed instruments all my life, cat gut, silk, or steel strings all make middle c at the same frequency of vibration

Sorry John but what does that have to do with the price of Tea in China?

Are all of those strings making middle C at the same tension? Nope not even close. I've been playing guitar all my life too. And I sure know that my nylon string's are putting far less stress on the fretboard of my Classical then the steel strings on my Ibanez. At the same exact tune. If the steel strings were as the same tension they would have much lower pitch (they would be less rigid) if you increase the tension (or make them more rigid) they will vibrate at a higher frequency.

Actually John you've helped me illustrate what I'm talking about, thank you.

[Flash]

That harmonic will on the middle of the cam spit the distributor shaft up out of it's mounts, yes it breaks the timing chain in front and can also do other physical damage, have also played stringed instruments all my life, cat gut, silk, or steel strings all make middle c at the same frequency of vibration

Sorry John but what does that have to do with the price of Tea in China?

Are all of those strings making middle C at the same tension? Nope not even close. I've been playing guitar all my life too. And I sure know that my nylon string's are putting far less stress on the fretboard of my Classical then the steel strings on my Ibanez. At the same exact tune. If the steel strings were as the same tension they would have much lower pitch (they would be less rigid) if you increase the tension (or make them more rigid) they will vibrate at a higher frequency.

Actually John you've helped me illustrate what I'm talking about, thank you.

I don't know too much about the the actual cause or theory but the guitar string sure help

If it is the torsional twist of the cam then a billet cam, would help dramatically on the chain snapping......like you had said earlier....But what cam material has the least torsional twist?

I know when i was talking to one of the cam grinder, they said that it had to go thru a long heat treating processes and that the cam would have to be re-straighten several time before the cam profile was cut into the Roller, billet shaft.

Is it possible that our cast cams are......kind of egg shaped from the factory...........and cause a out of balance type situation?

Flash.

[SIXPAK]

No, I do not believe that our cams are egg shaped. Cast cams do not have any kind if heat treating process that they are subjected to. Billet cams are all done to an oversize state before heat treating. After that they are straightened, journals reground to correct size to remove any residual amount out of round and straightness.

[John]

Yes increasing tension will raise one of the frequencies affecting our strings or camshafts. But there is several things to
look at, example the timing gear set and chain pitch distance sets up natural frequencies, loading of the camshaft throughthe valve train as well as vibrations induced from all components come into play. Changing from bell bronze to phosphor bronze will have effect I don't know how much. We both recognize the critical major at 5600 rpm and increased torsional
resistance might be capable of raising this point to the 6500 rpm range, but the alloyed cast iron used in flat tappet cams is noted for that characteristic. I wish I knew that answer. The long length camshafts had limitations in the old flathead
inline 8"s and 6's, various dampening systems have a well known history. If we look at the Navarro camshaft pictures closely,
you note it is not visually that different than ours, if you research the custom camshafts of it's day you will find they
were usually the same material as ours, Formula 1 racers were using them of the same materials. But you will also see that
Barneys fuel pump mounts solidly to a custom cast timing cover and is driven from the camshaft, Adding one solid point of
vibration dampening to the camshaft. I think that might also raise the critical failure point rpm? Going to play with this some on down the road. I have thought too much about this ever since I read Lee"s thread about camshaft failure and the modifications to prevent this.
John

[Flash]

Do you have a link to this discussion or are you referring to the one gave above?

How about a link of so, I would like to read it also

Flash