I posted on ls1gto.com earlier, but figured Id share my misfortune over here too. My weekend started out wonderful Friday nite. Vehicle is a 2005 GTO M6

Just finished installing my Harrop Diff cover and was heading home down the highway about 55-60 mph. Started to hear a small tick (like a primary off the header leak) That quickly turned into a louder tick. Turn car off and coasted to redlight, started back up and nursed to my house (aprox 1/4 mile from where redlight is at).

Once home I quickly located tick to be coming from left bank, top of head. Took apart and found this.....










Farther inspection found that AT LEAST 1 pushrod is toast. The head and valve cover have been chewed into, and I do not know the condition of the lifter on that valve. I also do not know if any damage was done to the engine by it running with a dead cylinder.

The last hard run I did was on Aug 20th @415 pm, and it was in 3rd gear, for about 3500-4000 rpms. The rockers are stated to be good for RPM up to 7200, and for stronger spring pressures.

Now my car is smurffed good. Have to flush the crank case to get all the aluminum debris out, which wastes the AMSOIL currently in there. (still had 2000 miles til next oil change)

Quick answers to questions that will be asked.
* parts were all purchased at the End of April and the begining of May.
* I run roller rockers due to running Trick Flow heads.
* Car has never been tracked
* Heads, cam, rockers, pushrods have 5700 miles on them
* Installation was followed per Terra's instructions- very similar to the instructions found here- http://ls1howto.com/index.php?article=21
* Other than the failed rocker, no other contact to heads/valve covers have been detected.
* Aprox 4500 miles, rocker torque was rechecked. Perfect.
* Ordered all parts from repitable vendor, who is know for wonderful engine builds. (trying to contact now)
* Using a 7.500 pushrod, as Trick Flow says to. Preload was set according to both the Yella's instructions and the instructions linked above
* Springs used are the one standard for Trick Flow heads. Dual's with a .650 max lift.
* cam used is- 240/244 .605/.596 112 LSA
* Stock bottom end LS2

 

Subscribing...

Christian

 

Bummer! Royal PITA now.

 

Same thing was happening to me. I broke four YT's. I ended up replacing them all with stock LS1 rockers. Runs great, for now.

The only issue remaining now is that Tony Mamo is telling me that the stock rockers, since they are not roller tips, have too large of a sweeping area on the end of the valve. This, he tells me, side loads the valve and causes premature failure and excessive wear on the bronze valve guides. I have been concidering different options, but Tony and Doug (Doug is the sole guy (I am told) in the US who orders the YT's from AUS) are trying to get me to have the YT's replaced. I don't have time to deal with replacing these things all the time, so I am asking to be credited my money back or just put it towards a steel (poss. Jesel) set.

In my sig you will find my set up. All of these rockers broke within the first 3,000 miles, and all when I was cruising in 6th gear at 60 to 65 mph. The first broke at 600 miles. HERE is the link to my FB page of my SS and the broken rockers.

In case the link does not work:
http://www.facebook.com/album.php?ai...4&l=b733bd4eef

 

I was about to say that you aren't the first person to break one. I've seen a few people break them.

 

Intresting

 

I find that YT's instructions are confusing at best. Additionally, ls1howto is wrong as well. I took your photo and marked it below. From the photo (you will need to check closer) it appears that your wipe pattern is skewed to the intake side and the rockers need to be shimmed. This will then require longer pushrods. Not sure if this had anything to do with the failure, probably not.

What are the spring forces at seat and open?

Did you verify pushrod to rocker cup clearance, especially if the pushrod is not one with a 270 degree ball?

Also, check the exact opposite rocker on the other side and make sure there isn't contact with the head. Look for marks on the rockers and valve covers. I had issues with the rockers hitting the valve covers (mine are shimmed quite high) and this required significant grinding and sealing of the threads for the coil pack bolts. Use the other side to aid with diagnosis since has not had a failure at this point.

 

I was running the shim that came with the Terra's. I will recheck the sweep pattern on another valve tip. Yes the instructions were difficult to go by. But I took my time, read several other HOW-TO's (link 1 of them) and then proceded to go about the install. I spent the better part of a day (some where about 4-6 hours) on just installing and rechecking the rockers.

The springs are the standard springs in the assembled Trick Flow heads. Dual's with a .650 max lift. And since I am running the Trick Flow heads, I can not run stock rockers. I have to run roller rockers.

I had Yella Terra post on my LS1GTO thread. They are going to replace the rockers at no charge.

 

We have seen quite a few break. I have since switched to using Harland Sharp rockers or the stock rocker mod and have had great luck with both.

 

well Im going to run the Yella's 1 more time. They are replacing the entire set for me. IF it goes again, i will be making a different decesion on roller rockers.

 

if it were me, i wouldnt run the engine, until i poured some diesle down that side of the engine. that way its forces all the pieces to the oil pan to drain out. then i would put oil in it, run the car (under a light load) till it reaches operating temp. and chaing the oil. it would be sad to see you get it all back together and have a bearing failure. but thats my .02

 

I have many of the larger pieces out already. They were caught in the top of the head. I plan on draining the oil, flushing the left head with K-1, and then doing an oil change (not running the car with K-1 obviously) Amsoil is quite expensive to change out.

 

u could run like pezoil platnium 5-30 just for that light run to soak up the remainig k-1. its the small pices to worry about. they can make it through the oil pick up into the oil pump, before it gets to the filter.

 

good point. I will run some 30w (break in oil left over) thru, then do an oil and filter change.

 

FWIW, here is how I set mine up. Note that the supplied shims did not result in a good wipe pattern. Shims are used to set up the geometry (wipe) not the lifter preload. The pushrod length does that. So step 1 is to set geometry, step 2 is to measure for pushrod length.

Link

 

Very interesting read. I will try your way, but will have to do in car somehow.

I fell that the 2nd pic at the end is the way mine are set. (which according to the wording of the Yella Terra install sheet, is correct) I see that the 3rd pic is better tho

 

It can be done on the car, I have done it that way as well using the same method. You will find if you play with the shim height the pattern will narrow right up at the center. I used some washers until I got the right height, then I ordered shims. Since YT is replacing yours, you could get the shim height now that way when the new rockers arrive you will be ready with shims and pushrods should those require a new length since a change in shim height will dictate a change in pushrod as well.

 

IDK maybe some guide plates would of kept things together, looks like some bouncing around went in there. Not sure you can use them with the shaft mounts. I run the new cranes for an LS3. Also maybe consider some 1511 behives with the Alum. rockers, unless the lift is 650+. the lighter the better is not a bad thing. Just as long as your not crushin seals. Good Luck.

 

Guide plates with shaft rockers are incompatible.

 

Why would I downgrade to a single beehive springs when I already have a set of dual springs with a .650 max lift?

What makes you suspect that there way "bouncing" arround in there? Other than where the roller rocker broke, everything else is perfectly fine. When the rocker broke, it caused the pushrod to bounce arround, but only after the rocker broke, not before.

I dont think guide plates would have held together the roller rocker on this one.