ckpitt55

iTrader: (4)

Thanks for the info Tony. While absolute rigidity is definitely good I think I'll stick with what I have if you feel that's sufficient. After all I've got less aggressive lobes, less spring pressure, 1.7 ratio, less lift, etc. etc. on my setup.

Thanks for the info - I will be running the YT's.

Also, awesome info on the stockers. I like seeing hard numbers like this instead of the typical hand waving that goes on...in for more info/discussion. Just curious, how did you decouple lobe lift from valve lift in your measurements?

therabidweasel

iTrader: (5)

So to be clear I was inspecting just the rocker. I located the fulcrum (and everything else) optically. Then I measured the distance to the pushrod cup and the distance to both sides of the rectangular scrubbed patch at the tip. The near side of the patch is at the beginning of the VE and the far side is at peak.

There are some details of the measurement that arent really worth describing, like accounting for different focal planes etc. This is admittedly a fairly simplistic view of the rocker, but I was encouraged the ratio was centered about 1.7 after I had done all the focal plane geometry etc...I did not calculate backward, those numbers fell out.

In particular I am not certain that my measurements of the PR cup account for what is going on...perhaps some scrubbing occurs there. I assumed point contact at a fixed distance to the fulcrum even though I noted some scrub marks, primarily on the circumference of the cup. I convinced myself that was probably due to valve rattle or low pressure in the lifter at startup. But who knows.

Id really like to compare to what someone with stockers measures for lift with a solid lifter. Its all academic for me because I run aftermarket, but I find certain design aspects interesting and if I can supply useful info to the forum so much the better.

PS the reason I kept mentioning the cam is because it determines how large that scrubbed patch is. The larger it is, the bigger the variation in ratio. Thats my contention anyway.

therabidweasel

iTrader: (5)

Hey while we are on it, Tony I am super curious of the alloy of the YT rockers. Im something of a materials guy and one look at all the dendritic structures visible on them (that roughish look) it is clearly not "just" aluminum. I would imagine it is not cryo heat treated because that normally reverses at engine temps. Is it some kind of hypereutectic or something? Just curious, its clearly something special.

ckpitt55

iTrader: (4)

Got it.

I think your fixed distance assumption is pretty valid, not sure of how much you'd gain from a more detailed analysis there. Even if the pushrod does shift off center, I'd wager that it wouldn't be more than but a fraction of its diameter - a much smaller value as compared to the shift in contact on the valve side of things from valve open to valve closed that you saw.

Thinking about this some more, I'm sure some amount of scrubbing does go on at the pushrod cup. Theoretically there should be no slipping if the pushrod was perfectly centered (on both the rocker and the lifter) throughout travel, but I'm not confident that it is... the rocker sweeps out an arc whereas the lifter is traveling up and down along a singular axis. Geometry dictates that the linkage between the two would "sway" back and forth if that makes sense, such that the cup "rolls" about the tip of the rod - probably the reason why we don't have "pushrod guides" because the sideloading would wear them out at an extremely fast rate. I think pushrod deflection would also impart some component of lateral loading there that would contribute to your fulcrum shift - obviously something exacerbated by weaker pushrods and higher spring pressures. I'd expect the point contact condition to be maintained, but these two effects start to take shape as the lifter rolls up onto the opening ramp.

Irregardless of those effects, it sounds to me like you have more than enough measurement resolution to detect meaningful changes in the lift ratio through travel. Some of it is just inherent to the mechanics of any rocker design (sweeping out arcs), and some to the way the rocker contacts the valve. I'd bet that if you'd measure a YT rocker in a similar fashion, you'd see a similar shift in ratios but it wouldn't be nearly as bad since you're able to achieve a much much narrower contact patch to begin with.

Here's a few pictures I came across. I like pictures.





In the second one you can see the arc it traces out and the averaging of ratios that happens just due to the different intersection point between the arc and the centerline of the valve. Similar thing on the push rod side. As you said, the more lift you have the more variation in ratio you're going to see.

Tony Mamo @ AFR

iTrader: (13)

Its just the finish left from the "tumbling" process they use for deburring and stress relief.....I was curious myself because they do have a kind of unique texture/finish and Jim told me that was from one of the final op's they do on the rockers. I'm not sure what type of actual aluminum extrusion they use.

-Tony

PS....I have two of my most detail oriented customers in the same thread together....this should be fun....LOL

Chuck meet Steve.....Steve meet Chuck (Steve is already enjoying the goodness though....his combo is up and running. Chuck has to play catch up but he's making some good headway of late....pun intended!)

ckpitt55

iTrader: (4)

...currently competing for the title of world's slowest engine builder

sabersaw30

iTrader: (10)

Do a search on the yt's people have not been having good luck with them.

ckpitt55

iTrader: (4)

This isn't the first time I've researched them. But of the 245 threads with reference to "yella terra" on this forum, only a fraction discussed rocker failure, and only one of those discussed supposed failure of a new design rocker. It was a 1.8 ultralite that saw failure of the roller needle bearings. Unknown whether proper geometry was checked / set or not or if the 1.8 ratio was appropriate for the heads being used.

Expanding that search to google, "yella terra failure", every single thread that came up on in the results, here and from other forums, were of the old design.

Here's my thing- if they're still as bad as everyone seems to think, then I should be able to find some evidence of that. If you're able to find something I haven't been able to in the past 6 months then by all means, link me up...I'd love to see it. Until that time comes it seems that a decent portion - if not all - of the lingering concern is baseless.

therabidweasel

iTrader: (5)

[QUOTE=Tony Mamo @ AFR;17503970
-Tony

PS....I have two of my most detail oriented custmers in the same thread together....this should be fun....LOL

Chuck meet Steve.....Steve meet Chuck (Steve is already enjoying the goodness though....his combo is up and running. Chuck has to play catch up but he's making some good headway of late....pun intended!) [/QUOTE]

Hear that Chuck!? Tony Freaking Mamo called us two of his most detail oriented customers! Ill take it, but I know some of the others and my little build is a joke compared to those. Glen has more horsepower at one wheel than what ive got at the crank. Hey like I said I will totally take it...Tony just wants me to beta test a meth system anyway

Tony, roger on the tumbling...but it sure looks like something more than that to me. Hmmmmm.

ckpitt55

iTrader: (4)

Hey I'm just a noob with too much time on my hands, but I'll take it too lol. Would never have made it this far without people like him though.

P.S. -- YT ultralites are aircraft grade 2024 aluminum. http://asm.matweb.com/search/Specifi...ssnum=MA2024T4

And an article on the effect that shot peening (tumbling) has on the fatigue performance of high strength aluminum alloys: http://www.shotpeener.com/library/pdf/1999025.pdf

It's science! lol

Tony Mamo @ AFR

iTrader: (13)

Its ancient history for the most part....

There was a bad batch of the first Gen design that really caused alot of grief for them (and the end users of course)....an end mill with a sharp edge versus a radiused edge the culprit there.

The second design (with the end mill issues resolved) was much more reliable but guys with ALOT of spring pressure and guys with not enough (valve float jarring and beating stuff to death) caused some failures at the front of rocker arm by the pushrod cup.

Their newest design has that area beefed up more and is a more balanced rocker arm as well. Thats been out about 6 months now....maybe even more....time flies but most of the YT failures were years ago from the two issues I just previously mentioned.

No part is bullet proof, especially a part with "Ultralite" in its name.....LOL

Lets face it, "light" isn't normally associated with bullet proof but understand that for a hyd. roller valvetrain to effectively spin 7K or so with no valvefloat, the rockers must be light. At the end of the day I feel the YT's are an excellent compromise (especially the current crop) between reliability, and ultimately functionality because if they dont work well and you go into valvefloat by 6600 they really aren't worth purchasing in the first place.

This is an item that a fine line has to be walked or reliability would end up hurting functionality. Their old rockers never broke but they were clubs and valvefloat would creep into the picture between 6000 and 6300....they just didn't work that effectively in a hyd roller application and thats when I got the ear of the new owner at the time, sharing my experience with him and suggesting he design the first rocker system specifically designed for hyd roller applications aimed at the LS market.



-Tony

ryridesmotox

Hey Tony, What do you think about the Comp gold rollers? I have an LS6 that I want to put a new cam in and have the heads machined. I have no problem running either but I can get a better deal on some Comp golds through a friend. If they aren't as good as the YTs then I'll end up getting YTs.

adamantium

iTrader: (3)

It blows my mind how people can post and chime in on stuff they've never physically dealt with or have done personally. I hate the tech section on here sometimes. Glad we have guys like tony mamo around to weed out the BS and implant first hand experience and knowledge when needed.

Tony Mamo @ AFR

iTrader: (13)

I think the Comp system is a studmount style set-up? If so I would probably steer clear. Honestly....you cant beat the proven performance of the YT's....for a few dollars more you know they are going to work. I think they are the lightest aftermarket rockers out there, yet strong enough to last a reasonable amount of time. I had an engine I built for a customer 4 years ago.....he put almost 40K on this thing and finally broke his first Yella Terra at the nose (the 2nd Gen design's Achilles heal).

We opted just to replace all of them with the Gen III design so he could forget about any other potential failures with high mileage rockers.

Also guys....lets be real....performance never comes with a factory 100K warranty.....you cant expect half that out of most performance parts including our own heads. At 50K you would have to rework the guides and freshen the VJ unless you were **** with frequent oil changes and had the valvetrain really dialed in.

Its just par for the course as they say....you have to go into this with some common sense

-Tony

ryridesmotox

Thanks Tony. I apprectiate the feedback

01ssreda4

iTrader: (96)

I've seen a lot of failed parts. Hardly ever do you see a stock rocker/valve failure under .625 lift. That's fact. Is the pattern shitty? Most likely, doesn't mean it will be detrimental to the engine though. And the latter is obviously gonna be most important to the masses.

LS1-450

iTrader: (33)

By light or ultra-light, I a$$ume we are talking the weight of the rocker tip. Would like to know the difference between the tip weight of the ultra-light vs a stock rocker. Have also not seen mentioned the importance of using thicker walled pushrods in order to prevent pole vaulting pushrods on high RPM high spring pressure builds.

Tony Mamo @ AFR

iTrader: (13)

We are talking about the weight of the whole assembly.....the rocker itself is light on both ends and has a huge trunnion (which is fixed and doesn't move so its not part of the rotational mass/inertia).

Running beefier pushrods is a separate topic altogether regardless of rocker arm. All of my builds run them but its not really pertinent to the conversation IMO (we may as well start talking about the intensity of cam lobes then.....all of this just related to valvetrain dynamics).

Also, the guys in the past that had problems with the Yella Terras.....its just as documented that the company replaced most of them for free and no one had severe engine damage from the failure.....more of an inconvenience than something to lose sleep over like breaking a valve spring and dropping a valve.....that has potential fail written all over it.

Its almost a Coke and Pepsi thing.....both work....but my advice is to spend the extra for the slight bump in HP (from less deflection and more lift/duration at the valve), and the massively improved wipe pattern netting a small fraction of the side loading a stock rocker imparts on the guides/valvetrain etc.

Stock works....but the YT's offer the end user some worthwhile perks

-Tony

LS1-450

iTrader: (33)

Tony, I did not say anything about a broken YT or that stock rockers were better or worse. Simply asked for a weight comparison since roller tips are typically heavy. Respectfully disagree that pushrods are a seperate topic since the discussion has moved from PRW rockers to YT rockers & "most detailed customers" setting up their valve train(s).

ckpitt55

iTrader: (4)

LS1-450.....found this from another thread

Stock rocker: 8.2 grams
Crane 1.8 roller rocker: 22.8 grams
Harland Sharp non-adjustable 1.7 roller rocker: 22.5 grams

I think this is Jim from YT - this might be for the older arms though (thread was from 2007)

Tip weights:
Stock LS1 - 8.2 g
YT (older designs) - 15.5 g

Tip and reciprocating weights do not tell the entire story though - you've got rotational inertia which is extremely important as well, if not moreso. For instance, its possible for a lighter arm to have a higher rotational inertia. But without having the model to analyze in cad and determine some sort of mass distribution vs. distance from point of rotation it'd be hard to populate a meaningful comparison between the stockers and YT's.

Given what I've seen of the new design, I'd expect the overall reciprocating mass to go up slightly since they bulked it up in the area around the trunion. This would not have much of an effect on rotational inertia since that increase in mass is concentrated so close to the point of rotation (think of the mass as a torque arm). That being said, I'd wager that the stock arms are better in this regard. We need spintron data for the YT's.