Nobody hating on them. I have them and ran them in my now decommissioned 346. I was responding to the stronger than steel comment. I am a professional metallurgist. The statement was technically untrue.

I presume Tony knows what I was referring to.

 

I know Darth.

 

Yes....thanks for chiming in (again!)

I am in fact specifically discussing the Ultralites as my HR "purpose built" rocker.

Something else I wanted to add was that it would be really easy to make a rocker that never breaks.....but the problem with that is it becomes too heavy and can start promoting valvetrain instability.....not the desired result.

Its a very fine line between enough heft to be durable and light enough to work great and pull good RPM with sorted out valvetrains. IMO the current rocker arm is just that.....a perfect balance. Once in awhile a Gen 3 breaks but its extremely rare and I would rather have that situation than a set of heavy rockers that effect the power curve and never break

Also guys.....its a rocker arm....if one breaks its not (typically) a catastrophic event......sure its an inconvenience and a Triple A tow home but your back on the road quickly. Again.....understanding the delicate balance of strength versus durability (not to mention an attractive price), I just dont know of any other products that can meet all these goals. Im sure if a set was built in titanium you could have everything (really strong and durable and extremely lightweight) but the guys reading this post (myself included) dont want to foot the bill for that set of rocker arms.

Again....purpose built for our specific needs at a price most people can live with.

I should add if any of you guys have a broken Gen 3 rocker, I will replace it for you at no cost whether you purchased them from me or not. Just hit me up via email, PM or phone and we will make it happen for you.

And I knew where Darth was going with the comment he made but feel another 10 seconds typing to expand on it would have gone a long way.....LOL

Regards,
Tony

 

Tony, I'm a little surprised you are not using the ultra lite pro version.
I think these are lighter and stronger than the normal ultra lite, unless yours is a custom build.

 

Yeah, you're right. There's a whole longer discussion that likely needs a thread. it just trips a nerve, because I deal with materials lunacy on a regular basis. Like - make the metal stronger and more plastic. Well, that's like saying make the paint lighter and have more black pigment.

So to be very clear, I think the YT is a fantastic product for its price range and intended use. I also think that the roller tip helps to increase low lift duration due to the more "progressive" ratio of stock rockers (as you lift, the contact point moves away from the fulcrum, so the ratio is not as constant). I ran those rockers in my 346 build, never had an issue, and was quite happy with them. I still have them. I also got the upgraded rocker bolt option that Tony offers, and I think the increased stiffness of the rocker bolt is well worth it. When I ordered my cam from Kip, I had to get a different set of shims to accommodate the bolt, and he said, "well that's a tremendous ides" regarding the bolt upgrade. To my knowledge, that is a one-off thing you have to order through Tony (not 100% sure on that, but I am like 87.3% sure)

But knowing rocker mass and other variables, I also like to run lighter valves. And also, do not discount spring mass. People tend to ignore the mass of the spring, but the spring has to control itself too.

Anyway, this is a far cry from the 434 build it started as, so... /rant

 

I run the 8mm bolt yt ls3 rocket arms. At 7800 rpm I show no sign of instability with stainless valves. I like the yella terra rockers, just not easy to find covers to fit over them.

 

I run the pro street with the 10mm bolts.
I also have stainless valves but I will only run my engine to 7000rpm as I have a long runner manifold.
Good to know everything is stable at that rpm.
Yella Terra sell spacers to suit their rockers.

 

I’m interested to know what happened here:



https://ls1tech.com/forums/dynamomet...results-3.html

 

Like Tony said, very low breaking rate but parts do break.

 

Did this end up being a clearance issue?

 

I truly hope it's a failed rocker. That's the easiest fix.

 

Bryan was at COTA, and he wasn’t exactly putting around. Race cars break parts. This is the first Gen3 YT I’ve seen break personally. I’ve seen aluminum Jesels break. Nothing is break resistant under high stress, high rpm race conditions.

 

Aluminum rockers will fatigue over time. I got a good deal on these with my custom Daytona nascar prototype ls7 spec heads (flat machined rocker pedestal like ls1/2, not vette ls7). They look strong to me. They also look bulky in this crappy pic I took but in reality they are very small and light. the support bar weighs a ton though compared to stock ls1 rockers

 

I don’t accept the notion that parts just break. There is always a reason. He got very little use out of them so I doubt it’s a fatigue issue. He had some good guys set it up and look it all over so I doubt it was an installation error. Seems like a product defect to me.

 

Not sure how to explain it, but looking at the break (in the other thread about this), you can see where it just plain broke, but also parts that look crystallized, like a fault existed in the grain structure before it actually broke.

 

Rough texture simply indicates fast failure mode. smooth texture indicates slow failure mode. An example of slow failure is like when you run a press brake and shear a metal plate very controlled. it will have a smooth surface. When there is an abrupt failure - like the end of a rocker breaking at RPM, it fails very quickly and has a rough texture. That "crystalized" look is stretched metal at the point of failure. Errors in the atomic lattice can only be seen with SEM. Inclusions and weird grain structures require an acid etch and a microscope. Often cracks can not be seen with the naked eye without an acid etch. Nital is typically used, but I've used about any strong acid to get the job done. Nital is safer to work with than muriatic and other commercial strong acids.

Obviously something made it fail. Honestly for the OP, best thing would be a material defect, as that means it's less likely to be any of the potential horror stories we can all come up with to explain it. You can follow the lines of the failure to where they all converge and that is the point where it started to fail first. Interesting tidbit there for you.

FWIW, a fatigue failure has a smooth AND rough texture. The slow failure portion (early int he fatigue failure) is very very smooth and often shows corrosion on steel parts because it has been exposed for a while. Then, the part starts to fail faster, so the texture gets rough. It's roughest where the last bit of material was hanging on. Not ruling out fatigue, but I'd want to see the thing in person or else some very good pictures to call it fatigue.

What's honestly most likely if it was not anything mechanical? Assuming that the rockers are machined from billet aluminum, a casting defect in the ingot or billet (depending on the casting method).

Likely nothing in this post did anyone any good, but failure analysis is an entire field of study.

 

Thank you Darth, that was a great explanation!

 

I’m glad that I don’t have any aluminum rocker arms in any of my engines.

 

That's how I feel. In the tens of thousands of miles I've done in my modified LS cars and how I drive, there's no way any aluminum rocker would have held up. It's 2019 and these are street/strip cars with roller cams that get driven hard and turn high rpms they need steel rockers and I don't care who I offend in saying it.

 

I'm just about finished with this build, I'm still undecided about what intake to use. I was thinking about that new fast hi ram intake but who knows when it'll be available. Another option is the lod intake. Another option is a ported fast but they don't seem worth the money over a stock intake. Here are the specs on the cam that I'll be running.

241/250 .629”/.615” 114 LSA +3

Any recommendations are links to similar builds with ls3 heads.