Mez

iTrader: (1)

A friend of mine with Trick Flow heads had a YT fail after only a few hundred miles. His motor was built a well respected shop in Houston.

I wrote YT and they informed me that although they are rated up to 7200 rpm, the maximum open pressure they recommend is 420 lbs. So the first thing people should do is make sure the valve springs they use are below this.

The second thing to look at is the rev limit. Just because they are rated at 7200 rpm does not mean people should rev it that high because they could experience valve float. When you get valve float, YT said the rocker could see 480 lbs open pressure momentarily. In the case of my friend mentioned above, the shop that tuned his motor set the rev cut off at 7000 rpm but the motor made max power at 6200 rpm. We believe he hit the rev limit, experienced valve float with the Trick Flow springs that were rated at 380 lbs on his cam. We reset the rev limit to 6500 rpm and everything has been fine since.

I have YT on my Lingenfelter Corvette with the LS2 with about 20,000 miles with no problems. I have a Patriot Gold springs rated for .650" because I have the Lingenfelter GT11 cam with lift of .631" intake and .644" exhaust. I also use the Comp Cam Hi-tech pushrods to eliminate any flex which also could cause instability. The spring pressure at this lift is rated at ~380 lbs. This car made 473 rwhp on the last dyno tune at 6100 rpm. I have my rev limit set to 6500 rpm and try to shift just below that.


My recommendations:
A.. Make sure the cam and springs you are using keep open spring pressure to under 420 lbs at maximum lift. I suggest under 400 lbs. for safe measure.

B.. Make sure your rev limiter is well below valve float. If your motor makes max power at, for example, 6100 rpm there is reason to go above 6500 rpm so set the rev limiter to that.

GrannySShifting

iTrader: (10)

Has nothing to do with spring pressure in my experience. Rocker arm sets built a few years ago I have ran 450+ open pressure and 7500-8000 rpm on with 0 failures. In the last year half or two there were some rockers built with an issue, all the breakages occured in very short timeframe, maybe 1 or 2 rockers in a set, and if they made it past that timeframe all seems to be fine. Some with low 340 open pressures and sub 7000 rpm - 0 valvefloat. I dont think I have had a failure in any recent production sets

ArthurJGuy

iTrader: (1)

Mez I have heard the same issue in reguards to spring pressure recently. It appears that the YT's first point of failure is a small fracture and that allows them to contact the head causing total failure.

I've noticed several of these failures are on TFS heads, and I suspect it's because TFS heads come with a 450# open valvespring.

onefastgator

ArthurJGuy,
What do you mean the Yella Terra's have a small fracture? Can you show me what you are talking about? I have installed many sets of these rockers (without any failures) and have never seen a fracture.

Mez,
What are the cam specs on your friend's car?

ArthurJGuy

iTrader: (1)

The fracture is a failure, so if you have never seen a failure it stands to reason you have never seen a fracture either.

I wish I would have taken more pics of mine, the rocker right next to it had fractured but not contacted the head yet, it was DAMN close though.

onefastgator

Arthur,
I see you edited the other post to read broken rockers. It didn't say broken before so I was looking at the post as if it was stating that all Yella Terra’s have a fracture. Thanks for clearing that up.

As far as the 450# of spring pressure, Yella Terra has their Platinum series rocker for those applications. This is right out of their catalog: Designed for the most severe applications Platinum rockers feature “wide body” arms for even greater strength and resistance to deflection. All Platinum rockers feature heavy duty 7/16” mountings for unsurpassed rocker stability.

ArthurJGuy

iTrader: (1)

Yes, but they do not publish the rating of the entry level rockers until you break one and call to complain.

sabastian458

iTrader: (5)

Bumping this older thread due to my replacement set breaking last night. Will keep everyone updated as to what happens.

Yella Terra failure round 2

sabastian458

iTrader: (5)

Here is the response recieve from YT with pictures.

YT response

edge04

iTrader: (9)

interesting! I had a YT rocker go bad, replaced it and now had another one go bad. My is different as it's not fully breaking, just the cup (see pic). Not sure why that is. Odd thing is that it's the same one on both sides. I am running the Trick Flow 235 heads with their springs. I have TF 7.5 push rods. It's an LS2 with MAGGIE TVS2300 supercharger with about 13lbs and 625 rwhp. It's a blower cam 222/230 .597/.600 115 lsa +2. YT said that I have too much motor for those rockers?? I want to replace them all now but not sure with what and wondering if something else is the problem. I will replace all the push rods while I'm at it. Should I go with a different ration than 1.7?

sabastian458

iTrader: (5)

Can you get a clearer picture, I'm having a hard time seeing the failure.

What lifters are you running? I know with my TFS with LS2 shorty, I had to change to a 7.550 push rod to get right in the middle of the preload spec. Not sayin that the cause, just something to look into next time you go back together. I am now going to recheck mine when the new rockers come in. Last time all of this took 2.5 weeks from day of failure to day of repair.

edge04

iTrader: (9)

look at the bottom rocker. If you look at the cup where the push rod sits, you will see the center of the cup laying right next to it. Compare the cups. Same thing happened on the same rocker on the other side. Glad the piece was just laying in the head.

edge04

iTrader: (9)

Typically when the seats break like that it is from impact or the parts not rolling correctly and skipping slightly causing impact. So i'm guessing that the push rod was not swiveling correctly in the rocker arm maybe because the length and tip type was not correct. Should I look into a little shorter push rod?

It looks like push rod length and wear pattern is correct right?

sabastian458

iTrader: (5)

On my setup it was perfectly set up. First time around I went off faith and it broke pretty quickly. I then bought the pushrod checker tool and measured everyone at least three times and bought the proper pushrod to obtain the correct preload without going over .100. I also setup the swipe pattern several times on both banks to make sure I could get as close to center of the valve tip as possible. I was in the drivers head again last night and wiped each valve tip off and the pattern was spot on center.

edge04

iTrader: (9)

I'm starting to believe that the YT ultralights are not capable of withstanding my set up. Going to try something else and see.

Mez

iTrader: (1)

Do you guys know Yella Terra changed the Ultra Lite design around June 2010? Basically, they beefed up the area around the pushrod cup by 10%. The older version has the "1.7" stamped in the middle under the pushrod cup. The improved version has it stamped to about .25" to the right of center.

Everyone should check which version they have.

edge04

iTrader: (9)

Mine is stamped to the left

sabastian458

iTrader: (5)

That is the set that I just broke, still the early style.

Mez

iTrader: (1)

Below is the difference between the two versions. This illustration was sent to me by Yella Terra.

edge04

iTrader: (9)

based on my invoice date I have their old version. But rather then continuing to break them or replacing them all I might as well go with a different product.

If i stay with the same 1.7 ratio but change manufactures can i stay with the same 7.5 PR lenght?