i just got some 1.6 ratio roller rockers from a friend and i have a summit cam specd at 214/224 442/465 i was wondering if the stock heads will be able to take the amount of lift and how much HP do you think i would gain?

 

1. Yes
2. dont know,

 

On factory heads that haven't been modified for lift, no it won't work. It's pushing it on the intake side. Probably going to hit clearance issues on the exhaust side.

 

I didnt mean to post as I wasnt sure..but it posted anyways.

 

You posted before the morning coffee, huh?

Anyway, as to gains, the gains will be from the lift for the most part. However, the general rule of thumb is: the lazier the ramp rates, the more duration the rockers "add." And summit cams aren't the most aggressive cams out there, you might gain a few at .050", however, again, the gains will primarily be for the lift. Can't give any concrete or even semi-concrete estimates, though, sorry. But the rockers would definitly be worth it if you could afford the clearance.

 

The main effect they will have, is to make the valve action more consitent feom one to another. Stock rubber rockers are highly flexible, vary greatly in the flexbility of their rubber compound from one to another, and due to molding inconsistencies and tolerance during curing and vulcanizing, have considerably different dimensions from one to another. I recall back in the Civil War days, we measured some with a dial indicator; on the particular motors we had, the actual measured ratio of valve lift to lobe lift varied from 1.38 to 1.45, with most of them around 1.42 or 1.43. It's also interesting to watch stock ones with a Strobotach; you can actually watch them bend. See that, and you will never run a stamped rocker again.

 

Gives a new meaning to the word "horsepower."

 

 

Yeah we already had "class racing" back then; there was a standard 1 horsepower limit. It wasn't very hard to verify that in tech inspection.

 

so what type of clearance issues am i going to experiences

 

can i get a response as to if i can do this because i want to install theese roller rockers will this lift work on theese heads?

 

Factory heads, not modified for the extra lift: No it will not work. The bottom of the retainer will hit the top of the guide boss.

 

how do i get this to stop from happening

 

At those lifts, they probably won't interfere.

Put one pair of the rockers on, on each side; one intake and one exhaust. Turn the motor over slowly by hand and look at the clearance between the bottom of the retainer and the valve guide. If it's OK, like .060" or more, then .... it's OK. If they hit, then ... it's not OK.

Some people will grind the retainers. Personally I won't do that. The right thing to do, is to machine off the top of the valve guides.

 

Think about that. If you can actually see, with your unassisted eye envelope deflection on any single rocker, that it's highly likely that plastic deformation will soon follow on that rocker. And that means rocker failure. This seldom happens though, either in stock engines or even in factory performance-parts sourced high performance engines, even after 100,000 miles and hundred of millions of valve cycles. So there is a flaw in taking what you've seen, by unmagnified eyeball view, and jumping to the conclusion that the stamped steel rockers have a rubber-like behavior. You are undoubtedly seeing large displacements if you can see that kind of wandering behavior of a rocker, but it's not associated with rubbery deflection during the important part of the valve cycle.

The limits of the wandering behavior would be determined by the type of valve guiding: self-aligning rockers would be limited in lateral (non-pitch) movement by the gap width difference of the valve stem and the rails on the rocker. If the gap with were 50 thosandths, then the rocker could wiggle within 50-thou translation, and hence within an arc having 50-thou motion at the valve tip end. If the rocker used guide plates, the non-pitch rocker motion (that part you witnessed) would be set by the clearance between the pushrod and the guide plate.

When you use a Strobotach, you are trying to not only match the firing of the flash lamp to the engine rpm, but you also want to phase the firing of the lamp so that you get to watch the important motion of the valvetrain. The only imporant part is AFTER the slack in the lifter/pushrod/rocker/valvestem is taken up, and then during the lift/lowering motion.

IF you are also observing rubbery motion duriing the rest of the cylinder valve motion cycle, than what you are witnessing is a random walk of the rocker when it is not under load --- so strobe photography (or strobe visualization with your eyes) won't tell you anything at all. Of course the rocker would walk all over the place, and give the appearance of being rubbery. Because the motion, when unloaded, is not repeatable and therefore useless to view with a strobe lamp of any kind. AND we would have to likewise test your theory, with either optical measurements of the valve stem, or measurements of the valve motion to see if not all of the 1.5 ratio (or 1.43 or whatever the actual number is) is getting to the valve. AFAIK, neither of us have that data.

Because GM factory rockers (at least prior to LS1 engines) are not shaft mounted, then there is no "pitch control", to use the aircraft term, for the rocker UNLESS and ONLY UNLESS the rocker is loaded and the valve is doing something. And even then, as I think about it, the rocker would require time to move back to apogee. That means the rocker motion, during the non-valve actuating part of the cycle will appear almost random -- and to the naked eye, rubbery. Even when you shut off an engine, and remove a valve cover, the rockers are not all parallel. Yes, I know that even stopped, they are in different cam phases cycles.... but apart from that, they aren't even parallel. THAT is what you are seeing, only it's not repeatable IMO with the Strobotach, because you are observing the random walk associated with the clearance method used to align the rocker. Shaft-mounted rocker won't exhibit this, other than the play on the shaft.

But it doesn't mean the rocker is rubbery and deflecting (or even rotation in pitch) in any way that deleterious to valve motion. The deflection of any stock rocker loaded with roughly 200 lbs of force will be so small that you couldn't possibly see it, and if you could, the rocker would fail from being deformed far too much and well into the plastic zone, where it would very quickly yield. I believe you are witnessing uncontrolled random rocker walk, and when the valve does becaome loaded, the rocker doesn't necessarily and instantly return to apogee above the rocker ball. It walks within the gap provided by the rocker guidance, and most of the time it doesn't want to make contact -- so there is little friction. So it gives the appearance of haphazard rubbery motion, but it has nothing to do with rubbery deflection of the rocker.

I know what I am writing runs completely afoul of the types of rubbery comments you've been making here on this subject for a few years now ---- but I don't think your observations with the Strobotach are meaningful, and I still don't believe the rubbery comment. We can disagree on these points, I don't intend to prolong an argument. But I did want time to consider what you wrote, and why I don't think it is right. For a highly loaded, high rpm valve spring, you might have a case to make but then pushrod buckling would also tend to confuse the observations. I don't think my comments here are the last word, but yours certainly aren't either.

I still maintain that a proper strength analysis of stock steel rockers, vs aluminum roller, vs steel roller has not be adequately done by anyone (except perhaps a company making roller replacements.... and they have a vested interest in NOT making that data public). It would make an excellent master's thesis at a place like Kettering, or in the Sloan Lab, but as far as I know, it hasn't been done yet.

Roller replacement rocker arms don't make much of a power gain on an engine [i]unless[/] it has a big cam with large static valve spring preload, when it becomes more easy to eliminate large sliding friction. The claims by the manufacturers are seldom met in practice. For most street applications, the roller gains are usually well above the rpm for peak torque, and negligible below that rpm. Mfg consistency on the rocker ratio is a point I won't dispute... but I don't think computer controlled manufacturing has the same slop in tolerances as it did say 30 years ago.

Anyway - a long post not intended to highjack the orig thread.... but it seemed better placed here than elsewhere.

 

Its nice of you to post your novel, again. But RB is right. The stock ones do flex. They do most definately give an unpredictable valve lift. It happens. If you dont believe it fine, thats your choice. Just stop wasting bandwidth posting this every time someone talks about "rubber rockers"

 

I posted in this thread once.
I posted what, once or twice in another in which you whined. If you don't like the novel, don't read it.

Again, do you have any evidence for this, or, are you just hand waving and repeating the hearsay? The Strobotach argument offered by RB to support the "rubber rocker" theory fails, IMO, for the many reasons stated above --- you got anything better? Are your eyes capable of measuring large rubbery deflections of stamped rockers? Instead of just whining about my novel, why not deal with the technical issues I mentioned? Do you even understand them? Do you have enough of a technical background?

It is an alternative opinion that your narrow mind can't handle. You also have a lot more posts than I do so it looks like your doing most of the wasting here.

 

Do you have any evidence to the contrary? Can you show this? Prove to us that we are wrong, and you are right? I dont need to produce books and studies, I can show you real world experience. Take a car with stock 1.5's, dyno it and replace with a good set of aftermarket 1.5's, you will see a difference. Almost guaranteed. Argue till you are blue in the face it wont change matters.

I dont have a narrow mind. I am probably one of the most open minded people around here. Dont try to attack my post count. I spend my time here helping people and giving useful information. Not argueing that stock rocker arms are better than thier aftermarket competitors.

Post your proof, we would all like to see it.

 

Also, please refrain from attacking. You dont know me. You dont know my background and you certainly DO NOT know what type of knowledge I have. If you knew me, you wouldn't have even posted that. I havent insulted your intelligence, don't try to insult mine.

 

i believe they were originally called"rubber rockers"because the rub the valve tip rather than rolling across it.
Eric

 

No, they were called rubber rockers because of the way they flex. It isnt so bad on a stock engine, but when you put anything with a real amount of lift to it, they flex pretty good.