KLJ

The rocker arm I purchased looks similar to John's. I examined the brand new rocker pad surface carefully with machinists instruments and there is a slight convexity or crown like on a lifter. This means that a point contact is present and intended at least when it is new.

I am guessing that the pad is finished by pressing the cast face against a die of some sort. You can see the tooling mark on the reverse. The pushrod ball socket is machine finished.

There are at least three casting variations based on the shape and thickness of the vertical wall behind the pad.

Call the first variation the one seen in mine and John's.

Here is an example of the second; the angle is closer to 90 degrees:



Here is an example of the third variation; the angle appears to be 90 degrees:



Good luck with your investigations. Buying the rocker arm cost just a little bit more than an SAE paper. If someone needs a brand new rocker arm, please PM me and I will send it at no charge.

Dirty Howie

KLJ

Maybe I am the only dumb one here. But I honestly am not grasping what you are trying to show or explain. Can you try it again please ?


DH

AzDave47

Mopar Jimmy

100%

KLJ

I think these pictures will help. I believe the aqua or light blue design to be initial production. The red or orange one is seen in the February 2009 Popular Hot Rodding article. The lavender or purple one is current (as in the one I just purchased).

To explain why these changes might have been made:

One possibility is that the physics sims used to model the sodium filled exhaust valve and its dynamics were not sophisticated enough at the time of initial design. Remember that liquid sodium is bouncing back and forth chaotically in the stem of the valve.

Expert systems use empirically gathered data to more closely model reality.

Varying mass concentrations or distribution is an old trick notably used, say, in NVH improvement of engine blocks. It seems probable that this is in use here to disrupt destructive resonance of the valve/sodium-movement/valve spring/retainer/rocker/pushrod/lifter/cam system.

Why? Perhaps exhaust valve guide wear or valve failure data from the field? I should stress that this is purely speculation. I am very sure, though, there are people reading this that know the answer.

Good luck with your investigations.

Pb82 Ronin

To me, I think he's trying to explain why there are so many issues out there with rocker arm geometry is because there are so many variations of rockers for the same engine. Just a guess...

KLJ

When I study designs of engine components over time I look for elements being manipulated. With critical reasoning applied, this is usually a window into unspoken issues.

For example, examine the head breathing/drainage ports in the Ford Modular V8 engine over decades. Then focus in on the culmination of this in the Coyote 5.0. Even within the small dataset of pictures available during the development the size and shape of ports was being varied. This is all related to secondary windage flow patterns and oil entrainment.

If you become familiar with the technique of analysis you can apply it to other systems, such as the one under discussion in this thread.

john_g_46

Look at the 4 sided cutout in the rocker around the rocker bolt. It is at quite an angle in my and KLJ's stock rockers. Less so in the second photo and square in the third.

John

Rock36

Do you suspect this might also be related to the part number shift for the LS7 exhaust valves a few years back?

I don't think we know what those specific changes were aside from the part number, except IIRC the weight increased slightly...not sure about the weight though.

john_g_46

My guess is that they have increased the twist that will occur at the end of the rocker, causing it to drag a little more on one side vs. the other...thus imparting more spin force on trhe stem, resulting in a higher spin rate for the valve.

Just another educated guess.

John

KLJ

There also seems to be a tacit assumption that pure sodium is being used rather than an alloy. http://en.wikipedia.org/wiki/NaK

You would have to perform careful detective work.

KLJ

I thought about that but the trunnion connection to the bearing set has so many degrees of freedom -- more than I imagined, that is for sure.

Rock36

That would be interesting to know.

I've been interested in the specific differences between LS6, LS7, and LS9 exhaust valves. So far open source info is very limited. Though I know NaK was used in the LS6 valves, presumably the LS9 valves too.

Also, the exhaust valve diameters are all different among the three engines, with the LS7 having the largest diameter valve of course. Aside from that, there is little out there. But anyway, don't want to get off topic anything, these subtle changes in the rockers are interesting to me too.

Katech_Zach

I don't know I don't even read this anymore. Yes, I think it's a waste of time. I just got an alert that somebody used the word Katech so I checked it out.

'06 Quicksilver Z06

Interesting.

Also now it looks like we are about go change gears and call it a rocker arm problem. Guess people will start to check to see that the angles inside the opening of their rockers are all right angles now.
So would "the tool" identify this?

john_g_46

A visual inspection reveals the evolution of the rocker arms. Some of the rockers have excessive radial clearance as well and allow nearly 1/4" travel over the stem...a serious problem as well.

The primary root cause discussed in this thread remains an obvious geometry problem detectable by a simple witness marks test. Guides worn beyond spec remain detectable by a simple wiggle test.

Here's a simple fact: A bunch of folks in here have performed these simple tests and over half of them have found guides worn out of spec. Jason's comment assures that I and likely very many others will avoid doing business with him in the future.

John

wolf8218

'06 Quicksilver Z06

Well not to speak for him John, but he might be wondering how many in this thread were doing business with him before, and how many would have been doing business with him afterward anyway.

And of those who would have done business with him, how many would be calling him up after the sale hounding him about this topic?

I don't agree with everything that Jason and Katech say either.

But their Torquer 110 is in my car and is probably one of the biggest sellers in terms of cams on this forum. Their ti/mo exhaust valves are also starting to generate buzz in here.

Their LS9x clutch and their timing chain are in my car too.

Like many, just because I don't agree with everything they say, doesn't mean I boycott them.

I don't believe that his comment is going to hurt Katech's sales at all.

Indeed I appreciate that he gave a straightforward and honest answer, without pussyfooting around. And in fact, I expected him to respond to the questions Howie put to him, in the manner be did. The man was asked what he thought. I appreciate and respect him more that he didn't lie.

To say otherwise, would mean that Katech's "fix" of bronze guides, new stock exhaust valves, and new ti/mo intake valves, amounted to essentially barking up the wrong tree.

Clearly he doesn't believe that and does indeed believe in their fix.

That is reassuring to his prior customers. That he is standing behind what Katech believes to be the fix.

Dirty Howie

KLJ
Thanks for the explanation

Jason
Thanks for your definitive response

John
Well if there was any doubt, you now know where Katech stands

Quick
Well he certainly lost John !!


DH

john_g_46

Not that clear to me. Who would want to have a bunch of dissatisfied custumers coming back to them. Better to discredit what is now an obvious problem...although it was a difficult one to uncover.

John