Rocker arm recommendations?

Not sure strength in numbers is a good thing if your talking about lemmings. It's like science being settled by consensus and not accurate data.



A perfect rocker is something that can't be improved upon. Technology will always find improvements, but math is math. No one ever came up with a math equation that changed the outcome of natural law. They just discovered a formula to explain the outcome. It just shows how insignificant we are in the universe.

With todays technology, a "perfect" rocker is one that transfers the cam information to the valve with the least amount of wasted motion or losses. You call this ratio change, but it is not. It is simply the result of angularity introduced into the system through arc motions. No matter where you check the rocker in it's rotation around it's axis, the lengths remain the same. (Have you watched the video I linked to yet?) A perfect transfer of cam lobe information wouldn't use a rocker arm at all. Overhead "bucket" type cams come to mind.

Using your logic, a small block Mopar, which does not have a pushrod that follows the trajectory of the lifter (it's on a different angle), the loss of lobe lift at the end of the pushrod would mean that the lobe is getting smaller, therefore, less lift. That would be utter nonsense, but somehow, because you see losses at the valve, all of a sudden the rocker arm is losing ratio, and the fulcrum length is getting longer or shorter. Utter and complete nonsense. It is called Trigonometry. You have to understand what the "whole" system is doing before you can attempt to make a better rocker, or make a claim that someone who does understand the system is wrong. Back up through the system to see where the losses actually originated, instead of automatically assuming the ratio changed. This is where Smokey went wrong. He observed a loss at the valve, and then noticed the fulcrum sweep which led him to conclude there was a ratio change. He never investigated beyond the fulcrum for the origin of the losses. Had he done that, he would have found that pushrod/cup angularity, from sweep and rocker design, was reducing the input, and thereby, reducing the output as well.



Ok, you keep beating this old nag. Just shoot her and put her out of her misery. There is no valve side ratio or pushrod side ratio. But, because you insist, here is a test question for you.

Henry has a Jesel NASCAR SB2 rocker arm that has a .545" roller tip and has a 1.620" fulcrum length and a .575" offset. What is the ratio of this rocker? (For informational purposes only. Specifications are random, and do not necessarily reflect an actual Jesel SB2 rocker arm.)

If you want something to really make your head hurt; (this may not seem relevant, but it really is)

Three salesman travel to New York for a large conference. When they try to find a hotel room they find they are all booked. Finally they stumble across a budget hotel that has one room left, so they decide to share it. The young man at the counter tells them the room is $30, so they each pay their $10 and go up to the room.

Meanwhile the hotel manager comes back from a lunch break, and the young man tells him he rented the last room to three salesman. The manager asked how much he charged and the young man replied $30. No, no says the manager, that room is only $25. Take $5 up to the room and return it to the salesmen.

On his way to the room, the young man is thinking, "how am I going to divide $5 among three salesmen"? "I know", he thinks. "I'll give them each one dollar and pocket the other two." So, that's what he did.

So, the question is, If initially the three salesman each paid $10, for a total of $30, and they each got back $1, then they each paid $9. 9x3=27, so they paid $27 for the room. The young man pocketed $2. $27+$2=$29. If they initially paid $30, then what happened to the missing dollar?

B3,
Somehow I don't think you are going to get it.....

I already had it. And, once I learned something different, and confirmed it with dyno testing, I dropped the old way like a bad habit. Not going back, either. If you did a bit more research, especially concerning mid lift geometry, you might come away with a different perspective. Only a refusal to learn/change will stop someone from understanding the concept.

Post 67, where you are fixated with [ wrongly, for the umpteenth time ]: 'The length remains the same'.
It is not what I have written that is utter & complete nonsense....
You talk about ratio changing because valve lift is lost. Yes, you got that right. Ratio change.
Ummm, what?

With todays technology, a "perfect" rocker is one that transfers the cam information to the valve with the least amount of wasted motion or losses. You call this ratio change, but it is not. It is simply the result of angularity introduced into the system through arc motions. No matter where you check the rocker in it's rotation around it's axis, the lengths remain the same.

Bewy, you are dillusional, I never said anything remotely close to that. Either that, or you don't really believe this stuff and just want to keep yanking my chain to get a response. Your credibility is taking a serious hit when you can't quote me accurately in the same thread. No wonder you got Smokey's quotes wrong too.

that is not the only thing that happens with the rocker going from valve closed to valve open. Two other things happen concurrently:
- both the p'rod side & valve side travel through arcs. There is lost motion on both sides of the rocker due to the arc motions that are transferring a circular motion into a straight line [ prod & valve move essentially in a straight line ]. Depending on how the particular rocker is dimensioned will affect if & how much valve lift is lost.

Where have I heard this before? Oh yeah, in my tech articles, as well as in this thread which is my previous quote. That is called sweep losses, and not ratio loss. Thanks for confirming my work.

- using a ball/ball prod as an example. The prod ball is a smaller radius than the rocker cup. How do we know? Because if the ball was bigger, it would not fit inside the cup, or would jam. The ball makes point contact inside the cup; the ratio on the prod side is that length from that point of contact to the fulcrum centre. And it changes as the rocker moves through it's cycle, changing the ratio on the prod side. And the position of the contact point in the arc also causes a change in rocker movement & therefore ratio.

And yet, there is a straight line through the pushrod and the center of the adjuster radius, no matter where the rocker is in it's arc motion. But we are not to believe that the center is the point of rotation. SMH.


The combination of the change in the arc plus the contact point of the prod & roller tip is what gives the overall ratio & it changes throughout the rocker travel.
This is how the Crane quick lift rocker works; the prod cup is lower. That actually looses some straight line motion [ prod ] because of being further down the arc; but counteracting this is the fact that the ball contact in the cup is closer to the fulcrum pivot. The ball contact position wins out & creates the early lift increase.

If this was the case, it would be impossible for the rocker manufacturer to design a specific rocker ratio, so all those rockers advertised with a ratio is a lie.

The Crane rockers are a stud type rocker that has a lower pushrod seat, which, with a given pushrod length, will raise the fulcrum and increase rate of lift and velocity off the seat. I can do that with any rocker by raising the fulcrum point. The problem is, it does the exact same thing on the other side of the cam lobe, and closes the valve so fast it increases the probability of valve bounce and beats the seats out of the head. Just what everyone wants, right?

For those trying to understand the ratio change on the valve side. Imagine a shoe type rocker that is identical in shape to a roller tip rocker. Grind the shoe on the rocker to the same radius as the roller on the roller rocker. Now using the shoe rocker, the point of contact on the shoe changes during the rocker cycle. The ratio is the distance from the fulcrum centre to the shoe contact point it changes. Exactly the same thing happens with a roller rocker; it is as if at any time in the lift cycle, the roller is welded to the rocker arm & is as one.

There you have it! Throw all those roller rockers in the trash. There is no benefit to them.
This has been tried before (unsuccessfully), but just for entertainments sake, you should try it again. After all, who needs those extra moving parts that could fail if they aren't really needed.