WKMCD

Will do. BTW: 7/16th PR's are even better. (Shame about Terry Manton. Great guy!) Richard at WCCH opened them up when he did the Stage 3 porting on the heads.

vettenuts

OMG, I had no idea. I spoke with him on the phone a few times, he was so helpful. He even called me from his car so I wasn't waiting too long after leaving him a message.

WKMCD

Same here. Great guy who loved talking builds and knew his stuff. He'd been sick for a while and kept on working and helping people every day. He made me a set of PR's different lengths for intake and exhaust. When I mic'd the length they were spot on what I asked for.

sabastian458

Ok, heard back from Yella Terra at about midnight my time.

I sent him the video and one of the pictures of the rockers to Mr Jim Petrakis, who's contact information is in one of the linked threads. He informed me, and sent a picture of the new rockers, that the rockers I recieved just after my first failure were still of the really early design, that the new ones have additional material and strength in the exact areas where I have had my 2 failures. (The real early style having the ratio stamped to the left of the push rod cup, with some also being centered under the cup. The new ones are stamped to the right of the cup)

Mr Petrakis assured me 100% that I the rockers they are sending me will not fail as the others had. He has instructed the US supplier to drop ship me a whole new set of the newer style rockers at no charge. I am pretty happy about that, went alot easier than I thought it was going to be. I will keep yall updated on when they come in.

RonSSNova

All of US YT users appreciate the follow up!
Would be really helpful if you could photo the old vs. new side by side so we can see the difference as no doubt, there are still some bad sets out there....maybe mine!

Ron

sabastian458

Here are the pictures that were sent to me.




My rockers have the stamp to the left of the pushrod cup. They were produced in 2009, I would say somewhere around the early part of that year as I got them in Sept 09.


This shows the added material on the newer rockers. This is mine, and it is hard to tell, but it "appears" that mine have slightly less radius than the newer ones. I will try to varify the measurement off my old ones when I can.





So at this point, I am just waiting for my Bore Scope to be returned so I can go fishing for a piece of aluminum from the broken rocker. If I can not find it, the heads are going to have to come off, possibly the engine if I have to pull the whole pan. After all of that, and I get the engine put back together, I can remeasure for new pushrods again.

Mike94ZLT1

Those do look beefier!

miami993c297

And certainly a lot heavier...How much increase in MOI with the new version???

Christian

sabastian458

I think I can sneak a set of each to work and use the letter scale for the mail to weigh each of the rockers. I am sure it is a fair amount heavier, but if they dont break, I am ok with it. I plan on looking for a 3/8th pushrod, maybe bigger if I can get away with it.

I know stockers are lightest, but I feel uneasy about using stockers when TFS specifically states to use a full roller.

miami993c297

Only Spintron will tell, not your letter scales...or real live test, but it might be too late at this point...

Christian

vettenuts

I am sure that YT has not only done stress analysis to determine how to beef it up, but has a solid model as well. Can you ask Jim for the mass moment of inertia of the old vs. the new?

I just checked my photos, mine are the older design (bought in 2008). The other question I would have for Jim is if the new design shifts the geometry relationship between the valve stem roller, the shaft and the pushrod cup. If there is any shift, then new pushrods may be required.


One other observation, the larger radius under the valve stem end of the rocker will need to have its clearance verified during the entire valve stroke to ensure that it doesn't contact the valve spring retainer. Likely not an issue with beehive springs, but the doubles could be.

PS: Thanks for all the feedback and information.

C5Natie

OP, did you check or change the valve springs in those 3 yrs between failures? Thats a long time for springs with that size cam regardless of mileage. Thats usually when theyll weaken a bit a youll see vakve float and broken rocker arms.

sabastian458

No I have not replaced the valve springs, never really heard of having too before. I don't usually take the rpms up that high (5,000+) anymore either. I have no real way of checking the spring Pressures. At this point the heads look like they will be coming off (can't visually see the missing aluminum chunk) so I might look into replacing the springs at that time.

I plan on replacing all of the push rods once the new rockers come in anyways, so I will be checking the length with proper preload. I will of course let y'all know if they are of a different length.

Joe Vinci

I was going to say that I could tell by the way the rockers were stamped and the smaller radius that you must have inadvertently been sent another set of the early batch with issues. Anyway, I have sold and installed many sets of the Yella Terra rocker arms without any issues and have found their service to be second to none.

C5Natie

Even when the car isnt running the springs are compressed so they will fatigue with time. Most aftermarket valve springs last 15-20k miles or 1.5-2yrs, which ever comes first, at optimum pressure. Obviously less with more aggressive driving. Even with my PRC springs, TSP recommended I check them after a year or 15k mi. Most shops can do this for you pretty easily. This ensures that your springs are always at optimum pressures. Also depends what springs you have. Most LS springs on the market are weak imo. I like pressures of at least 450lbs at install height on a decent sized cam. What sucks is that this puts more pressure on the rockers and you start to see more failures. This is why even after having good luck with YT's on my LS1, I went with stockers and the comp cams bearing upgrade on my LS3.

leadfoot4

This comment might be slightly off the subject, but your comment makes me want to say this. I live in the NE (rust belt) and store my car in the winter. It's off the road for 3-4 months per year.

Many people simply throw some fuel stabilizer in the tank, yank the battery, cover the car, and let it sit until spring. I do not, for the reason stated above...the valve springs and/or the rockers can fatigue at a quicker rate if left in one position for an extended time. I start the engine and let it run for 15-20 minutes 2-3 times over the winter, to circulate the fluids, and hopefully, when I shut it off, everything is in a different position....

Mike94ZLT1

Unless you have a solid roller,, our hydraulic lifters bleed down over time, relieving pressure on the spring. Running your car for 20 minutes at a time while parked in your garage is a lot worse than just letting it sit.

leadfoot4

I respectfully disagree...I've been storing cars for the winter for over 30 years, and this is my normal procedure. Never had any issues...

lucky131969

Hogwash. Most people have no idea how extensive automotive testing is. Engine/powertrain design is tested in many environments, including months of below freezing operation, incorporating short operating times, where the engine never reaches operating temperature.

If it makes you feel better leadfoot4, do as you're doing. You will neither increase nor decrease the life of your engine.

RonSSNova

Thanks, I have the early style, 1.7 under the PR cup.......great.

Ron