It's quite possible you are not driving the car/motor hard enough. in other words, possibly the mild street driving is lugging the motor and rattling the engine, (detonation).
The only time I've busted valve springs and had rocker fall off is when the motor pinged/rattled/detonated. And you cannot hear that happening in most cases.

That's my 1st guess at it.

Karl

 

Agreed, I've never had a rocker come loose that I put on there. Really don't get how that could happen if they are done right.

Were the polylocks loose and easy to turn? Did the Polylocks back off or were just the rockers flopping all over with the polylocks still tight?

 

Exactly what I'm starting to think.

As far as I know, the first time it happened, all of the locks came loose. The second time, the locks seem tight, but the rockers are all over the place.

 

The worst part is, who ever did this combined the wrong parts or installed them incorrectly. I would be very worried after you get it back that its fixed right and want to run it hard like others are stating. The first time it went out what did they do exactly to fix the ptoblem? It sounds like they are over there heads and need to research this further before moving forward with removing the heads. You need to read some threads on here and educate yourself and maybe you can find the answer their fishing for. To bad you can't just get your money back and go somewhere else. Hopefully nothing else is damaged in the engine that won't show up right now.

 

Someone "reported" this post, because they feel it doesn't belong here. While this is not strictly "Advanced", it does illustrate the problems of dumping $$$$ into an engine, possibly not knowing what you are buying.

I think it can stay. If it deteriorates, I'll reconsider. I've been trying to get a little looser on what gets posted here, because the forum no longer seems to get much activity based on its original premise - Advanced Tech. Many of the really knowledgable "techies" seem to have disappeared. Stuff that obviously belongs elsewhere gets moved. This one is in a "gray area".

 

I am cognizant of where I place threads. And yes, I would agree that this question is gray. The problem is that it is obviously more difficult than it seems, as a supposed professional (my engine builder) is unable to remedy the problem!

Even in this section, it seems that a clear cut answer is not available. I think at this point that the actual problem is less important than coming to a general consensus that I have one or two problems at this point for sure. The first is that the combination of parts are incorrect. The second is that I have an engine "assembler" problem. When a so called "pro-engine" buider is unable to ascertain the repeated valve train failures, I thought it would be reasonable to pose the question here; especially since I have to decide whether or not to let this builder warranty his work, which to me will not likely be done correctly, or have another "more reputable" mechanic fix the problem and send him the bill.

Thanks for letting it stay.

 

your not going to get a clear cut answer...it could be a million different things....need to inspect parts...offer a complete story of exactly what happened both times.....None of us have any idea what parts were used or how they were installed.

Most obvious explanation would be the rockers are coming loose or your kissing valves. anyone done a leak down on it? Do that.......on a fressh engine most people run it and then check the valve lash again.....But it could be so many things

 

1-Determine the cause of rockers coming loose.
2-- Fix it!!!!!!!
3--Not a big mystery at all.

The polys are not tight enough,you are not paying attention enough to the sound of your engine when one does come loose,top of the studs are not flat,polys don't have enough thread contact,if ya don't have screw in studs then it is pulling the studs ('60's),the valves are sticking and letting the rocker jump off,guide plates not centered right.
Just a few to check and I would take it to somebody else and see.
Opinions are like as* holes everybody's got one,but that ain't curing your problem.

Get 'er done.

 

You'd have a lot more eyes on the problem in the LT1 section. But a "clear cut" answer to the problem can only be determined by first hand investigation, not online guesswork...

 

The first time the rockers fell apart, he was concerned about the compression. When he supposedly "fixed" the problem, I asked if he did a compression test. He then said "no" because he didn't think it was necessary.

Now it's 100-150 later, and he thinks I'm getting valve float? He's asked if I have floored it, and I have a few times, but the power falls off around 5000 rpm and won't shift passed 6000 rpm. Then he tells me the spring pressures were sufficient for the cam?!

Now he has no idea why it failed again, other than aggressive driving or valve springs not being up to the task. He's fairly sure now that the valves are bent! I now have loose rockers with lash caps missing. I also have a broken rocker that been turned with the tip resting on the edge of the retainer. The pushrod on that valve is bent at about 45 degrees.

It seems ridiculous that he would even suggest that I am the cause of the failures.

 

I would document as much as possible so if it gets ugly you have some ammo if you have to go after them. Getting a complete build sheet would be a good idea. Especially if they say they used expensive parts when they might have gone cheap. I know you can take it to someone else if they can't fix it and bill them, but at what point the law allows this i don't know.

 

I have cancelled checks and a parts list for most of the parts and labor. I also paid part of the motor in cash, but it would still be fairly easy to come up with an itemized list of everything. I saw almost all the parts go into engine during various stages of assembly.

The guy seems honest thus far, so on one hand, I would like to give him the opportunity to make it right, on the other hand, I don't want him continuing to exacerbate the problem if he's not competant in resolving it in the first place. As far as the law is concerned, it's a civil matter. I'd have to pay out-of-pocket expenses to another mechanic for an interim fix. My amount of recovery would be determined by a judge.

 

Let's keep this on topic..... TECH, not amateur lawyer stuff. Otherwise its gone.

Also sense a bit of negativism with your "Even in this section....." comment. People are trying to help you, and yet you can provide little if anything in the way of detailed info regarding the specific components used in the valve train, how it was assembled and adjusted, etc. Seems odd to put down the people who are trying to help you.

 

You said that you got to see most of the parts go into the engine, would you have any pics of the build that you could show us...someone might notice something odd in one of the pics.

Just a thought, b/c any info you can give will help out with determining your problem.

 

I'll soon post some pics of the damage. I actually have pictures of the valvetrain before and after, but only on the initial set up. Unfortunately, they're low quality because I took them on a camera phone. One thing the builder said was that he thought I was getting valve float. He's not sure if the springs are good enough. The springs on the engine are the springs that come with AFR LT4 210 cc race heads. I purchased the heads new in Jan, 2006, so I'm not sure if AFR is using a different spring as they improved the LT1/4 line up shortly after my heads were purchased. My cam lift is 636-616 with 1.6 rockers, the duration at .050 is a 248-254 on a 110 LSA. Maybe the cam is too big for the heads?

Another thing that I can't figure out is why he used REALLY thick head gaskets (you can plainly see the head is off the deck by more than a millimeter). He says the reason was to drop compression, but why would that need be there if he ordered the pistons "custom" in the first place?