Dan_the_C5_Man

These aluminium rockers have a limit in regards to how much spring they can handle. The more aggressive the cam lobe, the higher the lift, the more spring pressure you need to control the mass.

If the cam lobe is too aggressive and / or the spring pressure too high, you can fatigue the aluminum body of the rocker over time, causing a failure. Then inevitably the next post on the forum is a picture of a broken YT rocker and people claiming that they are "junk".

YT makes other versions of the LSx series rocker, heavier-duty versions.

My advice - if you're going with an aggressive cam with a lot of spring, stick with the stock rockers or look at the T&D steel rocker, or a steel full rail system.

jammeejamm

the information i was given is these were designed for valve train packages with .700’ lift and an open spring pressure of 500lbs open.

i am curious to know if anyone has run these with a "big cam" like the ones i mentioned.

i do appreciate your advice though.

MTPZ06

The YT ultralites have a max open spring pressure of 400lbs. Lift, I'm not sure...but Dan would know...he's the resident YT expert. I'm guessing he has dual citizenship with Australia

vertC6

Yeah I have spoken directly to the yella tera rep here in the US and they're definitely not designed for .700 lift or 500 pounds of pressure. As Dan said if you're going that big you want the stock rockers or something like crower pedestal mount.

jammeejamm

those numbers were straight from yella terra, pretty much copied from the reply i received.

"Our hydraulic LS7 arms fall under our Ultralite-Pro Range which are designed for valve train packages with .700’ lift and an open spring pressure of 500lbs open."

i have a set of these and planned on running them, but am having doubts due to this thread and the size of my cam. i am not asking to be a jerk. i am asking to make sure i am not setting up for disaster.

Dan_the_C5_Man

Note that I didn't give any specific spring pressure values. When I asked the principal engineer and co-owner of YT about the spring I intended to run, his statement to me was "that rocker can handle anything under 400 pounds open, no issues". That doesn't necessarily imply that they explode at 401 pounds, or 501 pounds. Honestly, I think the truth is, "it depends". On the max lift question, these don't have the arbitrary rotational limitations like the stock pieces - the arms can rotate 360 degrees on the shaft. However, depending on the size of the cam you may have to clearance the pedestal slightly - it's definitely something to check during your assembly process.

I don't think anyone can give you a black-and-white answer. They're not going to have the ability to tell you how long the setup will last, how durable it will be. Will they last 10,000 miles or 100,000 miles? What's the use case - occasional spirited street driving, quarter mile runs or hours and hours on a road course at 6000 RPM?

Unless someone is running the exact setup you intend to run with the exact rockers, cam and springs, your guess is as good as anyone's - just try to make an educated one.

As mentioned before, the design focus of this particular Ultralite model is all around weight savings. They're basically trying to replicate the stock rocker functionality with a roller tip on the end. The positive message in this story is if you do push the rockers over the design limit and you do break one (or two), they usually break at the pushrod cup area, splitting the body at the bottom of the trunnion bearing case. That's usually a pretty benign failure and most likely will not cause you to drop a valve or damage other components in the valve train.

If you go for it, good luck, please report back with your success or failure.

RedZ4me

I posted this info a couple of months ago - I spoke to YT and Tony Mamo on the phone - both have told me the specific LS7 rocker can handle 430-440 open pressure with no issues.

double06

I think there have been 3 generations of the 6670. The first 2 based on the forum here had some issues. Then I guess 3 years ago they did a beefy upgrade (just like GM finally did with our axles) and I saw some pictures on the forum (a guy got from YT) of we added stuff here and there with note saying 10% better 15% stronger look for ratio on the right not center of rocker etc. So is the 500 pounds now based on the Gen 3 version?

jimbob8915

Reviving an old thread. I have a new set of YT 6670s, an mild cam with .651/.635 lift. I am going to install Johnson 2110 lifters and PAC 1207x springs to compensate for rocker weight and hopefully no bounce. Factory intake valve and del west hollow stem exhaust valves. Any thoughts?

Dan_the_C5_Man

Just coming back to this. How did your combo work out?