What is the stock rocker ratio for a 84 lg4 5.0 engine, i used the search and came out with nothing.

 

same as any other SBC, 1:5

try this sometime it migth save you some time and bandwidth

 

Well its supposed to be 1.5, but it will vary anywhere from 1.2 to 1.5, hardly every really getting to 1.5. Those rubber rockers are junk.

 

Technically, the stock ratio is 1.52:1 but because of production tollerances, it does vary a bit from rocker to rocker.

 

they usually fall in the 1.42-1.5 range. You will never have sixteen on one engine that are the same.

 

well in the summit mag they listed the 1.5 for the factory hipo's so i didnt think they were 1.5

 

That's because pretty much any rocker is considered high performance when comparing to the crappy stock rockers. Non-roller, horrible production tolerances, flimsy, etc.

 

Their "nominal" spec is 1.5.

Factory rockers are factory rockers ..... junk. "HIPO" or not. It doesn't really matter what Summit "lists" them as. They're all the same, as far as ratio goes; the only difference is whether they have the "self-aligning" rail tip or not.

In reality, they usually measure between 1.38 and 1.45; that's with one dial indicator on the valve, and one on the push rod. Most of them will measure around 1.42-1.43. I've never attempted to measure them without a real-world spring load; always with a valve spring; if you used some real lightweight check springs or something, they might come closer to 1.5, at least some of them. They flex ALOT. If you watch a running engine with a Strobotach triggered off of a spark plug, and vary the phase of the blink to "stop" the motion of the rocker, you can see them bend. Looks pretty ridiculous actually.

Although, some people who post on this board, don't believe that can be done. Which is real unfortunate.... for them anyway.... those are the kind of people that I hope are in the other lane when I'm at the track.

 

I can do the same thing with an ordinary pencil and a strobe -- make you believe that I'm bending the pencil. You don't even need a strobe --- a Fluorescent tube light has a strobe-like behavior from the 60 cycle AC provided to them. So do overhead lights in a parking lot at night. Move your hand quickly under that illumination and you'll see freeze-frame copies of your hand. Oscillate the pencil under that light at the right speed and you will think the pencil is bent --- A LOT.

The reason WHY you get fooled with the optical illusion, either using the pencil or with the "junk" rocker arms is that you are not watching repeatable motion. A strobe is only useful for pseudo- freeze frame on cyclo-stationary oscillations: i.e. motion that repeats in cycles but appears stationary when doing so. The rocker pitching-motion (the indented motion) is repeatable, at least as far as the cam lobe, lifter, pushrod, and all valvetrain clearances will allow. But the roll- and yaw-motions of the rocker are NOT repeatble because those movements are not constrained by the ball pivot, and only loosely constrained (within limits) by the pushrod guideplate or by the rails of self-aligning rockers. The clearances in the guideplate/rails does allow some non-useful roll- and yaw-motion of the rocker and none of that motions will be repeatble under stroboscopic observation.

I know it will be hard for you to let go of your "rubber rocker" theory --- it's just that, a theory and your main argument for supporting it is flawed. Your conclusion for explaining what you are seeing is flawed.

I've also mentioned (elsewhere, differrent thread) a secondary point (one that you've also ignored): for the rocker to bend in the manner you are witnessing (with your eyes), would mean that the rocker would deform permanently. That's also called plastic deformation for people that work in mechanical & civil engineering. The rockers still look the same after the engine stops -- ever wonder why? Because the rocker never really deforms in the manner you believe.

Lastly, this problem can also be analyzed in reverse: you say that you observe "rubbery deflection" of the rocker. OK, how much? A quarter of an inch? Then model the rocker as a beam in 3-point-loading.

Use an upward force at the ends, to represent the valve stem and the pushrod, and a downward force at the fulcrum position to reprtesent the rocker ball pushing down on the rocker. Use a channel-bar section modulus to represent the rotary moment-of-intertia, and use 29e6 psi for E and 0.284 lbm/(in^3) for the density. Use a reasonable force at the valve stem, say 200 lbs, sum the moments about any point on the beam to get the rest of the forces, and then solve for the deflection of the beam. You can use double canitlever analysis as an equivalent (deflection = P(L^3)/(3EI) for each end of the rocker, you'll obviously get more deflection on the long end than the short one. Then if you know the assumed lift at the lifter (say 0.300"), you can use the rocker deflections to calculate what really gets to the valve stem. And you can then compare the theory (crude, admittedly but we're using simple math and not FEA) with your direct optical observation. The numbers won't even be close, because the deflection of a steel rocker arm under typical street-cam-loading is miniscule and not observable with your eye.

None of this is hard if you've had statics and strength-of-materials, two of the standard courses a design engineer would have to take to get a degree suited to work as an automotive engineer.

If you haven't had any of those courses, then you really are out of your league in making assertions about stamped steel rocker arms. Direct visualization of ball-pivot rocker arm movement by means of a strobe can lead to very faulty conclusions, like yours, when it comes to rocker arm flex. None of your so-called flexible rockers ever looked permanently deformed did they? That's because they never got into the plastic zone, either from compression or shear.

I'm probably the person you are talking about. You must be young, especially with your need to win at the track. You can have it. I'll consider this a "win" if I can convince other readers (not you) that your argument is wrong and that there is nothing wrong with factory-type stamped steel rockers especially for street use.

It will be an even bigger win, for me, if can ever get into your thick skull that what you've been saying for 2+ years is wrong, AND especially to get you to understand WHY. The ONLY part of your comments that's been correct is the variability in rocker arm ratio.

Finally, consider David Vizard. He's been around a lot longer than either of us. He's written many books on modifying engines, and his books are not theory-based (like C.F. Taylor, or J.C. Heywood's for example). His books are entirely practical, with an occasional drift into theory. His Chevy cylinder head book covers all aspects of cylinder head modifications, including porting, valves, springs, retainers, rocker studs and just about everything else you can imagine. There is one large omission: he never talks about rocker arms. The reason is that the factory stamped rocker arms are adequate for street and mild-strip use, and it's the rest of the valve train that needs more attention, NOT the rockers as you've been trying to lead people to believe.

There is more evidence of that in Vizard's other book on modifying Chevy engines, which includes a build on 10 separate engines, with dyno data on each. So even if you don't like books (a troubling attitude I've seen before on 3rdgen), you can still learn something from the engine buildups and the dyno results. VERY few of those engines use anything but the factory stamped steel rockers -- again because they are adequate for the job. GM engineers still specify some of their performance engines with stamped rocker arms -- again because they are adequate for use for 100,000 mile or more.

It seems to me that for someone as knowledgeable as Vizard, with so much hands-on and theoretical experience, that he would make a HUGE point about factory rockers being so rubbery and flimsy --- IF they were what you say they are. But they aren't.

Vizard had proven by direct hands-on example what I've been arguing all along. And Vizard, for the most part, does not advocate unneeded parts purchases when the factory parts are sufficient, especially when the aftermarket parts choices won't result in any significant torque or power gains.

So Vizard, indirectly, doesn't agree with you either. And that puts me in good company.

So I post this as a counter-argument to your strobotach rubber rocker theory. No one has challenged you on this before, but I hate to see illusory observations taken as engineering fact especially on a widely read auto forum.

If you will take the time to THINK about what I have said here, and in another post, and deal with these engineering issues:

1. severe rocker deflection would have to lead to permanent rocker deformation --- that doesn't happen, at least for stock/street applications, and in some stock engine rule-based racing. Why? If the rockers were that "rubbery", why wouldn't there be MANY MANY failures in the valve train?

2. When are strobe measurements unreliable? Why? What would H.E. Edgerton say about this. (aside: I knew him; he was known as the father of modern strobe photography).

3. How much would a stock rocker deflect with the type of forces acting on it? Would it deflect more, or fail sooner, than a pushrod would buckle?)

If you DEAL with these before you charge off with a reply, then you might actually learn something along the way.

MEs and CEs, feel free to add to this or pick it apart as best you can.

 

Woooohoooo!! He bit!

The voice of inexperience will win every time.

Yes, I've had a few courses in my day; my majors in college were math and physics.

Since you have no experience in the matter, I'll tell you that what you see as you do the experiment I described, is the rocker spreading apart at the ball fulcrum. And of course, the dial indicator doesn't lie either.

Yes I'm pretty young. Thank you. And yes I've read many of the books you mention, and yes I've seen quite a few of Edgerton's photos, like the one of the rifle bullet exiting the apple. And yes, you're still wrong, and you can protest as much as you like, the facts still remain the facts.

Thanks!!

 

Thats funny. Nice way to insult someone who has more knowledge and probably is older than you. Still nothing wrong with em, huh?

Why havent you showed us your "smoking gun" then? Your proof that they work good? Show us your proof that they provide constant lift? You cant, because they arent even manufactured consistently, how can they provide consistant performance? You arent going to be convincing anyone on this forum, without some evidence, we are waiting.

Are you denying that rocker arms are inconsistant? I can guarantee you they are, because I have measured them. A simple search on the internet can yield plenty of documentations of inaccuracies achieved with stock rockers.

 

edited

 

Shifty, you cant be right, because you dont have a study to back you up