L6 roller rockers ...

[Z-Gad]

I have never seen them before, but I ran across them on Ebay....

 

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8025351528&fromMakeTrack=true

 

I had considered adapting some from another application a while ago, but never got around to it.

[dj paul]

hmmm.... these look interesting. im interested to see what people say about these. i wonder if they would be good for a turbo motor

[JMortensen]

I think Malvern was trying to develop those for quite a while. Might want to search in the L6 forum and see if anything pops up. I know katman has touched on the subject in the past, can't remember what he had to say about them though. It would be a great idea if it worked.

[dj paul]

http://www.compcams.com/information/Products/RockerArms/MagnumRoller.asp i think these are almost the same thing. supposedly in some applications they are good for 20-30 more horses. i would just like them to give the valve train more durability, even if they didnt give that much added horsepower. they also are supposed to reduce wear on the cams or something.

[olie05]

yeah, but don't you need cam designed for a roller rocker?

 

-Oliver

[JMortensen]

http://forums.hybridz.org/showthread.php?t=75759

I know there has been more discussion than that. I think Olie is right. I think you need a hydraulic lifter and a roller cam profile. Not positive. Hopefully someone who knows more will help out.

[Dragonfly]

I have one primary concern after looking at the pictures on ebay... weight/mass. Those weigh more than mine (which are lightened) and look like the would weigh more than stock and of course as soon as you start adding weight to your valve train you start to loose performance from the increased mass. The real question is if the gains from the roller are greater than the losses from the increased mass. For me personaly I would have to say no they are not, for someone who is running a stock valve train they may well be worth it.

 

Dragonfly

[olie05]

http://forums.hybridz.org/showthread.php?t=100770&highlight=roller+rocker

 

found this thread, similar discussion

-Oliver

[cheftrd]

yeah' date=' but don't you need cam designed for a roller rocker?

 

-Oliver[/quote']

 

Bingo. Not only profile, but surface finish and metalurgy are different. Cams for a roller typically have a very hard surface.

[260DET]

Is'nt the body of most roller rockers made from light weight alloy? Because of the weight issue mentioned by Dragonfly.

[BRAAP]

The optimal, or even just an adequate, camshaft lobe profile is WAY different for those roller rockers than it would be for the typical wiper variety rocker we are used to on our beloved L-series. The reason for this is radius of the surface on which the cam lobe itself must act upon. Just look at the diameter of the roller itself of those lifters. That roller has a pretty small radius, especially compared to the radius of the wiping surface of the standard Datsun L-series rockers. If you use those roller rockers on a standard Datsun cam designed for our OE wiper type rockers, the actual valve timing events WILL end up MUCH different AND the lift under the curve will be drastically different. Basic geometry here folks. If you used those rockers on a standard Datsun L-series cam not profiled for those rockers, you would loose performance due to the valve motion not being optimal any more. The cam profile needs to be ground to match that of the smaller radius roller. Granted, a roller rocker has some benefits, mostly in reduced wear, and also very small reduction in friction vs the wiper style. You probably could get Comp Cams, or Lunati, to grind you a cam with the profile you desire but for use with those rockers and then you would reap the benefits that rollers offer.

For those not fully understanding why the cam lobes need to be profiled, or shaped differently for Rollers vs Flat style, take a look at any V-8 flat tappet and roller cam side by side. If you look at comparable profiles, roller to flat tappet, (Yes, I realize there are NO exact comparisons between the two, this is just to make general point), These two cams are VERY radically different from each other. They are SO much different that even your wife/girlfriend who wouldn’t know the difference between a crank shaft and a lug nut, could tell the difference. This drastic visual difference is because of the profile the cam lobe needs to match the radius of the roller vs the very large radius that is ground on the bottom of the flat tappet. Yes, “flat” tappets are actually radiused on the bottom ever so slightly, even though they are called “flat” tappet.

 

Any how, I hope this helps shed some light on the rollers. Yes they are GREAT, but only if you can get a cam manufactured to match the radius of the roller…

[jeffp]

The roller rocker/cam setup is ideal for the L series engines, to quote a previous post :Granted, a roller rocker has some benefits, mostly in reduced wear, and also very small reduction in friction vs the wiper style.

 

That is the understatement of the year. MOST of the friction in the L series engine is the topend. Just in case you disagree, get a high lift setup, turn the engine and you can feel the resistance to the turning. Then disconnect the timing gear from the cam and turn the engine, Difference between night and day. Roller setups were designed to reduce friction, period! and the ability to slam open the valve at a much higher ramp rate then you could EVER get from a tappet/wiper setup to do.

The cam profile is like stated before, radically different, the roler cam brings the true meaning to the phrase "BUMP STICK"

Getting such a cam will require a custom billet to start with, but I need to verify that, you may be able to get by with a solid reground Nissan cam, (not gun drilled for the lobe oiler)

However, even still the lobes will have to be cut in the center of the lobe with a 1/4" cutoff wheel, about .200 deep, then welded, then ground to specifications to provide the hardness required to give the acm any kind of longevity.

Now these units are a 1.4:1 rocker ratio, so you will need a higher lobe lift @ the cam to get for instance a .580 lift @ the valve then if you were running the 1.5:1 rocker ratio .415 lift VS .387 lobe lift. So you are talking radical changes in just the lift, and then the overall profile of the cam as stated earlier will be so apparent even the novas nechanic would realize the difference.

The question then becomes, will you have a valve stem long enough to fit the head, and still have enough length to provide for proper valve spring compression, and not get spring binding.

The standard cam gear/chain length would be much different, and you would definetly have to have full adjustability of both the cam chain and the cam sprocket to correct for the valve timing and proper chain tension.

You would also have to have very good external oiling, to ensure the lobe and the roller bearing got the required oil to keep the parts from wearing out in short order. So to sum up, oiling, cam hardnness, ( I once got to see a roller cam when I worked at Sig Erson cams of a cam that came from Big Daddy's car that had soft lobes that ran 2 YES 2 seconds in the car and it was trashed) timing issues, chain tensioning issues, and finally valve stem length.

Remember, the rocker geometry has to such that it will NOT promote the tip of the rocker to fall off the lash pad, and spring pressure that would folow the rocker/cam profile and shut the valve properly, NO bouncing on the cam allowed! Still another parameter, like the stock rocker configuration, is that the roller HAS to be in the center of the lobe, no hanging off to one side of the lobe at all.

So if you can get all of those parameters met, then I say go for it, you will have the very best setup out there, just open your wallet very wide and drop all of the money out of it LOL.

[BRAAP]

Jeff,

I have no issues with the majority of your post, in fact, it was very enlightening, thank you. Though I do disagree with your interpretation of the friction developed in the top end of the Nissan L-series head. Please don’t take this as I’m flaming or slamming you, my intent here is merely to educate so others are also aware of what is mechanically taking place in the top end, this is not a slam or flame.

What you described as “friction” was mostly the resistance to opening the valves against the valve springs AND the fact that the hydrodynamic oil wedge that is ever present on a “running” engine, isn’t “entirely” present when the engine is not running, and you are trying to hand crank the cam without that oil wedge. If it were just “friction”, then those cam lobes and rockers would be completely wiped out in only a few hundred to a thousand revolutions of the cam itself. Also, if roller rockers were installed in this same scenario, you would feel essentially the same amount of resistance to turning the cam, (this is assuming the roller rocker cam was ground to match the same valve lift/duration curve as the flat tappet variety).

There is a very small oil film between the rocker and cam lobe on a running engine, hydraulic wedge, therefore on a running engine, the cam lobe never actually touches the rocker surface. In essence, that wedge of oil, (to quote a famous commercial), is like liquid ball bearings. The only friction present at the intersection between the cam lobe and the rocker is that of the oil, and that friction is very minute. Being as there is a great deal of pressure on the oil that is directly between the cam lobe and the rocker face, (resistance to overcoming the spring pressure and also the weight of the valve itself from being accelerated off the valve seat, inertia), the oil gets hot, from the pressure, NOT the friction. The roller rocker also has the same oil wedge between the roller and the cam lobe as well, though the amount of surface are that oil wedge takes up is smaller.

If you could pressurize the oil system and perform this hand cranking of the top end only, using a flat tappet cam and then with the roller rockers and matched cam, the difference in resistance felt to turning the cams would be so minuscule, it isn’t worth measuring or even claiming as a benefit from a horse power stand point.

In short, the only REAL benefit to the roller rockers is the reduced wear, (almost all the cam and rocker wear is on start up before the oil get a chance to build up), AND the ability to grind a much more aggressive opening and closing ramp therefore giving more “lift under the curve” as compared to comparable flat tappet cam.

 

I hope this helps and doesn’t muddy the waters too much more….

[jeffp]

Lubricant -- any substance interposed between two surfaces in relative motion for the purpose of reducing the friction and/or the wear between them.

 

Lubricity -- ability of an oil or grease to lubricate; also called film strength.

Film strength -- property of a lubricant that acts to prevent scuffing or scoring of metal parts.

 

Friction -- the resisting force encountered at the common boundary between two bodies when, under the action of an external force, one body, moves or tends to move relative to the surface of the other.

 

Hydrodynamic lubrication -- a system of lubrication in which the shape and relative motion of the sliding surfaces causes the formation of a fluid film having sufficient pressure to separate the surfaces.

 

Full-fluid-film lubrication -- presence of a continuous lubricating film sufficient to completely separate two surfaces, as distinct from boundary lubrication. Full-fluid-film lubrication is normally hydrodynamic lubrication, whereby the oil adheres to the moving part and is drawn into the area between the sliding surfaces, where it forms a pressure -- or hydrodynamic -- wedge.

 

Pressure -- force per unit area, usually expressed in pounds per square inch.

 

Ball bearing -- an antifriction rolling type bearing containing rolling elements in the form of balls.

 

Needle bearing -- a rolling type of bearing containing rolling elements that are relatively long compared to their diameter.

 

I guess it is all in the way you think about it. I look at the wiping action of the cam and rocker arm as friction. Oil is then used to reduce the friction between the two parts. This equates to the drag cofficient of the two surfaces, and the improvement of the drag cofficient of the two surfaces when lubrication is the applied to the two parts. Agreed that the lack of lubrication, and the pressure properties of the lubricant to seperate the two parts and act like a buffer between the two will result in damaged surfaces in short order.

However, when you look at the drag cofficient and the heat produced by that drag of two parts wiping across each other to the properties of the parts to a bearing, or needle bearing you can easily see the overall improvement of the drag cofficient, and the loss in heat produced by the wiping action of the two parts. Also dont forget about the friction produced by the two parts and the overall effect on all of the parts involved. The friction equates to again drag between the two parts, as the drag is increased, the energy required to overcome the drag increases, heat is then produced and you then go into the thermal properties that will again increase the drag of the two wiping surfaces.

I also agree that the significant amount of the energy is required to depress the valve spring. However the friction and oil wedge you mentioned, along with the pressure the oil provides to keep the two parts seperated is much more then you realize. If the two parts were totally seperated, then there would be no need of a hardened part in the first place.

 

While it is understood the majority of the wear of the parts will occur at first startup, keep in mind the parts will still wear over time due to the insufficient lubricating pressure of the lubricant in the first place.

You are correct, and you pose some very important points well worth considering, however overall I believe the bearing contact area from wiping part to bearing is much less due to the properties of the bearing, and the ability of the lubricating oil to provide sufficient pressure on the bearings to obtain the desired improvement in friction, less requirements of the lubricating oil.

Does that sound right to you? So waht does this all mean, you can ramp up the valve much much faster and maintain the opening significantly longer at a higher lift for an overall improvement in the ability of the pump to fill to capacity by reducing the drag on the components.

So what do you think?

[260DET]

What about valve bounce with these heavier rockers and blunter cams? L's tend to pull the retainers off the valves if you go to heavy springs.

 

Stating the obvious, a system is only as good as its weakest link.

[Tony D]

Screw all this "cam" and "rocker" B.S., I'm going to drive a hydrostatic pump and open the damn valves with a computer controlled electro-hydraulic actuator...

 

DEVAS System, screw all this extra metal crap!

 

Then I can alter valve timing based on throttle position, engine speed, rate of throttle position change, hell I can change the RATE of valve opening with that system.

 

Cams, Rockers, ADJUSTMENT---man, you guys are SOOOOOO 19th Century!!!

[BRAAP]

... I guess it is all in the way you think about it. I look at the wiping action of the cam and rocker arm as friction. Oil is then used to reduce the friction between the two parts. This equates to the drag cofficient of the two surfaces' date=' and the improvement of the drag cofficient of the two surfaces when lubrication is the applied to the two parts. Agreed that the lack of lubrication, and the pressure properties of the lubricant to seperate the two parts and act like a buffer between the two will result in damaged surfaces in short order.

However, when you look at the drag cofficient and the heat produced by that drag of two parts wiping across each other to the properties of the parts to a bearing, or needle bearing you can easily see the overall improvement of the drag cofficient, and the loss in heat produced by the wiping action of the two parts. Also dont forget about the friction produced by the two parts and the overall effect on all of the parts involved. The friction equates to again drag between the two parts, as the drag is increased, the energy required to overcome the drag increases, heat is then produced and you then go into the thermal properties that will again increase the drag of the two wiping surfaces.

 

*************************

 

...overall I believe the bearing contact area from wiping part to bearing is much less due to the properties of the bearing, and the ability of the lubricating oil to provide sufficient pressure on the bearings to obtain the desired improvement in friction, less requirements of the lubricating oil.

Does that sound right to you? So waht does this all mean, you can ramp up the valve much much faster and maintain the opening significantly longer at a higher lift for an overall improvement in the ability of the pump to fill to capacity by reducing the drag on the components.

So what do you think?[/quote']

 

 

Jeff,

“What do I think”, you ask? Well…. I think a “Thank you” is in order. Thank you. I have to agree with everything you said. Your explanation of the greater heat being produced by the drag of the wiping action makes total sense. If I understand your intent, I guess another way to sate it is, if heat is being generated, (i.e. between the cam lobe and wiper surface), it took some form of energy to produce that heat. In our cars, that energy comes directly out of the BTU’s available in the fuel during combustion. Now instead of all that energy that is stored in our gasoline being converted to tire smoke in front of our buddies house on Saturday night, some of it was consumed producing heat between the cam lobe and rocker wiper surface, i.e. the energy it took to create the heat of the wiping cam, is not available to smoke the tires. Now if we knew how much energy we would be saving with those roller rockers vs the flat tappets…..

Your post brings to light some valuable points, though I’m still on the fence as just how much of a benefit the rollers really are, or stated another way, how much HP will be recovered at the crank by virtue of the less energy being expended to the cam/rocker interface?

 

After re reading your last sentence a couple of times, I think I was able to interpret your point and understood it as follows...

The roller bearings, by design and function, will allow the two moving parts to function with one another, (as compared to the flat wiping surface of say Datsun L-series tappets), at given loads with less heat being developed even with the roller bearings smaller overall contact area, and as such there is, overall, less heat generated which reduces the demands made on the oiling system overall. Did that make sense? If that is what you said, yes, I agree 100%.

[BRAAP]

Screw all this "cam" and "rocker" B.S.' date=' I'm going to drive a hydrostatic pump and open the damn valves with a computer controlled electro-hydraulic actuator...

 

DEVAS System, screw all this extra metal crap!

 

Then I can alter valve timing based on throttle position, engine speed, rate of throttle position change, hell I can change the RATE of valve opening with that system.

 

Cams, Rockers, ADJUSTMENT---man, you guys are SOOOOOO 19th Century!!![/quote']

 

 

Ah, why limit yourself with 18th century Poppet valves… Lets convert it to ROTARY valve!! Or better yet, a valve that functions like the aperture in a camera!!!! No need for throttle valves then! Engine load is 100% controlled with the ECU controlling the duration this aperture type valve remains open, i.e. Pulse Width, much like our current fuel injectors are controlled! The end result would be CLEANER emissions, (ah, who cares about emissions right?), BETTER mileage, (again, YAWN…) and WAY more POWER!!! All from our ridiculously thermally inefficient reciprocating power plants… (Only if we could safely harness nuclear energy for our Z cars…)

 

 

 

 

 

 

 

 

 

…….Paul…. Paul… wake up….your dreaming again about those barbaric reciprocating power plants…AGAIN….…. LOL

[Mack]

I was reading most of this. not all of it admittedly, but most of it! anyway......

 

 

on most of the friction in an L series being in the upper end of the motor. I would imagine that is true. I read somewhere, on the internet no less, that the L series valvetrain saps as much as 150hp at 9000rpm;s. I myself find taht nuber to be a little on the absurd side of things, but oh well. all the roler rocker arms are doing is allowing the engine to run more effeciently, turning less of its pwoer into waste heat and friction.

 

BRAAP>> on your assertion that turning an L series by hand that most of the force required to do it is the result of the action of opening the valves, it is makes sense at first, but you also have to think of the fact that at that low of RPM's, turning it by hand, for every valve being opened, there is a valve closing, thus exerting the stored energy in the valve spring back onto the closing ramp of the camshaft, negating the opening valve. get what I mean? kind of, Im not sure I get what I mean, HA ha! All I know is that Ive been hit a few times when Ive left a wrench on a cam bolt and it suddenly "sprang" back at me!!

 

It would be interesting to see how much power a roller type arm would produce on an Lseries head. whoever wins this auction should keep us informed!

[Dragonfly]

Mack take a look at your cam lobes... the opening profile is different from the closing profile. Your cam is designed to open the valve quickly and close it slowly (reletively speaking) therefore it takes more energy to open the valve than is recovered from the spring trying to re-seat the valve.

 

Dragonfly