roller rockers

[lyonsy]

just about to build up a 250 2v for racing on dirt speedways and looking for buy some rollers to go with it.
looking on mike's site he has 2 that look to suit me the yella terra and the ras ones.
the ones iam leaning towards is the ras ones as i beleave the full shaft mounted ones wont walk around as much as the shaft mounted but separate yella terra ones.
ratio is not really to much of a worry as custom ground cam anyway made to suit ratio etc.
also iam not to familar with the oil through shaft design does this cause problems at high revs ie 6000rpm or there abouts?

 

[matt1967]

to me the RAS look flimsey, that's why I went with the Yella Terra's, not to mention, the Yella Terra's are Full roller, the RAS are only roller tipped.

 

[lyonsy]

so the yella terra are roller on the pivoit as well?
i whould of thought that running a bush there whould be better.
has anyone installed the ras ones on here

 

[matt1967]

so the yella terra are roller on the pivoit as well?
i whould of thought that running a bush there whould be better.
has anyone installed the ras ones on here

yes, the yella terra's rides on full rollers, tip and the piviot. better for high RPM. a guy on www.Clubhotrod.com says he scattered a set of the 1.6 Roller tipped rockers on his 200 6 IDK if they were RAS or not but, that's why I shyed away from them. he converted to a 302 after his 200 got too tired.

 

[wallaka]

But really--does having a full roller set make one iota of difference under 7500 rpm? Honda makes cars that rev to 9000 stock that have shaft mounted rockers without rollers in the pivot of the rocker arms.

I suspect the 1.65 ratio on the Yella Terras is what makes most people prefer them.

 

[matt1967]

I suspect the 1.65 ratio on the Yella Terras is what makes most people prefer them.

I doubt it, .5 ratio is like nothing when it comes to lift, might be .25 more or so lift, but you could get a cam ground that matches what you need. I bought the 1.65's because I knew they were the best that was offered and after you figure in the fact you get lifters and pushrods with them, there only about $100 more than the RAS.

really for consistant high RPM running a set of shaft mounted rockers would probably be best actully.

 

[lyonsy]

yeah thats why iam leaning towards shaft mounted as unlike drag racing this engine will be seeing anywhere from 5000 to 7000 rpm constantly from 5mins to 1/2 hour at a time.
i dont mind losing a few hp to not have a rocker break.
only reason iam changing from the early adjustable type is there not roller tiped.
one other good thing with those ras i can get 1.5 and 1.6 higher a dyno for the day and play.

 

[TCSTEVE]

Hey this might be a stupid question but i need clarification.
Can i fit roller rockers to my pre X 2V down the track without having to worry about the extra lift from the roccer ratio causing my pistons to hit the valves

 

[lyonsy]

your not going to be running over 300deg or 600thou lift?
if an off the shelf cam you will be right.

 

[wallaka]

Umm...the stock rockers are shaft mounted. So are the RAS and YT.

Anyhow.

Drift, I think that the Yella Terras would be better for controlling lateral movement since they are clipped in place. On the other hand, using stronger springs in the stock shaft would stop much of the movement.

IMO, neither the RAS or Yella Terra will make enough horsepower difference to be worthwhile over an identical ratio stock-type arm (like the $325 RAS setup Mike carries).

If there were roller rockers with corresponding cam grinds, going to a full roller setup would actually mean something. For now it's just the last piece for a high rpm package, not a horsepower maker. I could spend $545 on stuff that'll make a lot more power.

But if money is no object...the Yella Terras are what I'd go with.

 

[lyonsy]

nah iam not chasing hp in the rockers just reliability of being able to sustain hign rpms for sustand perods of time with out falling.
add to that its also in a dusty enviroment when its doing this.
i also have to worry about filling the rocker cover full of oil as well which a lot of engines do when ran at high rpm for long periods of time.
the yella terra ones are shaft mountd but only the inlet and exhaust on that shaft from what i can tell from the pics i have seen.
i was thinking the ras with shaft running full length of head whould move around less.
and i was more thinking side to side movement ie pushing the valve into the guide more then supose to and the flexing the shaft outaway from the valve.

 

[AzCoupe]

There's much debate as to if roller rockers add HP or not. Some say YES, others say NO. Same goes for the DUI dizzy. Personally, I'm not sure on the rockers, but firmly believe the dizzy does. However, to prove the point one way or another, we are planning to dyno a stock motor and a mild build, with and without to verify the results. Should prove interesting. I was hoping to have done the dyno test by now, but have to many other things on my plate at the moment. We also want to test different header designs, and the new aluminum heads.

 

[wallaka]

Cool. I was hoping you'd chime in sooner or later.

There is no doubt in my mind that roller components will add horsepower. However, the reduced friction gives such a small percentage of the total horsepower as to be inconsequential. That was my point. I've not seen a dyno test showing only roller rockers vs. traditional rockers; they always change to a roller cam at the same time so the comparison is applesranges. Roller cams can be ground with such aggressive opening and closing rates that the valve spends more time being fully open.

Maybe that could be a future project for you, once everything settles down... 8)

 

[AzCoupe]

Those are my thoughts as well. There have been dyno test done, but none on our little sixes, apples to apples. There is also much debate, and varied opinions, as to which modification yeilds the best bang for the buck. We want to test various components, one at a time, and as match systems. And there are many parts to test. For example, how much HP is added using a Holley carb adaptor funneled into the stock 1V log. Claims of 20hp have been made, but I find that hard to believe. How much is gained swapping to roller rockers, and does the build vary the results? How much power is gain using long tube headers, and shorties? Which is the better suited for our sixes. Long tube headers produce more torque and shorties more top end. However, considering the torque of the little six, which is actually better. Is more overall (average) power to be gained with a long tube header, or with shorties? I for one, would really like to see the results of dyno testing done in a controlled enviroment, with all things being as equal as possible. Its going to take time, money, and a lot of hard work. Yet I think it would be well worth the effort and expense. Especially for me, since I sell the parts. If a specific part proves to have minimal gains, is it a worth while part to invest in? Maybe, maybe not. However, we must also remember that not all products are solely about power gains. Some are designed to increase the life span of the motor, increase gas mileage, and reduce maintenence. Which is just as important. Our goal is to educate our customers as to what can be expected from each and every part we sell. It's a lofty task, but one that can be accomplished in time.

 

[matt1967]

another thing that could possibly be done, stroker crankshafts, which making a stroker motor would greatly increase the torque. just the cam would limit the amount of extra stroke. but going to 3.200 or 3.250 stroke shouldn't be a problem it only makes a 200 a 207 figuring in 3.250 stroke but on my dyno software, adds about 20 ft/lbs at peak.

 

[XFlow_Fairlane]

While reading the the Corky Bell turbo book I found some interesting stuff.

turbo cars don't like too radical of cams since the overlap is not a good thing. since you are limited then on your duration you need a fast ramp up cam WHICH a roller can't provide (this is in the inital opening..the first few degrees) due to the limitations of a roller on a cam lobe. He recommends running a flat tappet cam (solid or hyd) with higher ratio rocker arms to help speed valve opening. Granted this mainly applies to a street motor where you are trying to build boost down lower. a .400" valve lift will increase to .425" when going from a 1.5 to 1.6 ratio rocker all while having minimum effects on duration. Looks like free cam profile to me! I think this is where some of the strong power in the Gen II chevy motors comes in as they run a high ratio rocker.

 

[MLINE]

I thought one of the main reasons roller cams/lifters were used was they could provide a faster rampup.

If Corky Bell's statment is true can somone explain to me how a flat tappet is better in that respect than a roller??

While reading the the Corky Bell turbo book I found some interesting stuff.

turbo cars don't like too radical of cams since the overlap is not a good thing. since you are limited then on your duration you need a fast ramp up cam WHICH a roller can't provide (this is in the inital opening..the first few degrees) due to the limitations of a roller on a cam lobe. He recommends running a flat tappet cam (solid or hyd) with higher ratio rocker arms to help speed valve opening. Granted this mainly applies to a street motor where you are trying to build boost down lower. a .400" valve lift will increase to .425" when going from a 1.5 to 1.6 ratio rocker all while having minimum effects on duration. Looks like free cam profile to me! I think this is where some of the strong power in the Gen II chevy motors comes in as they run a high ratio rocker.

 

[Anonymous]

Roller tappets have a higher maximum velocity since they're not diameter-limited, but can't take high rates during the early ramp opening since it's side load.
There is a cross-over point where roller tappets offer an advantage, but it requires a minimum duration before you get it, and I'm not sure what it is in these motors.
The more cam you have, the greater the benefit. For a mild cam it does nothing but use up money and add weight.

 

[Anonymous]

The roller tip is less punishing to the valve stem and guide, but very little in the way of power.

The rocker ratio is not "neutral" i.e., anything it does can be done with the cam isn't completely accurate.
One advantage to the stock ratio is that (given stock shaft placement) the higher ratios are usually made by shortening the pushrod arm, which means its travel is a longer arc and its ratio change throughout the swing is greater.
Under ideal conditions, the shaft would be moved as well, permitting the pushrod lever to remain stock and increasing the valve lever but this is much more complex and expensive and still space-limited by the distance in the pushrod hole.
A higher ratio also changes the spring load balance between the lifter and the valve. Higher ratio rocker = more load on the lifter with the same spring. Sometime good - more RPM with the same spring - sometimes bad - easier to wipe the cam during break-in, etc. Be sure to tell the cam mfg. what ratio you have when asking for a spring recco.

The rockers don't rotate on the shaft, they only oscillate a few degrees and the difference in friction is almost nothing. The needle parts also wear faster since the needles bear against a hardened shaft. They're also very dirt sensitive - 1 bit a debris in there will crunch up the needles.

The roller pivot adds only 1 advantage: it needs less oil than a bushing, which allows you to restrict your rocker oil feed. If you have a bearing or top end return problem this might help, but only if you restrict the feed. How much? It could be very costly to find out.