Z06LINK

No I know I have to check the valve off of the seat. Thanks

Dirty Howie

Good info. Lets see if Jason or others confirm this.


DH

NORTY

You are right. Lubrication between the valve stem and the guide is key here. The heat from the valve is not transmitted to the whole valve. The heat is localised and stops @ the sodium cavity. This causes hot spots along the stem (prior to the sodium cavity.) These hot spots cause oil to coke (varnish, basically.) When the oil cokes, it ceases to do it's job. (Keeps metals from wearing and carrying away heat.)

Don't know what "overkill" oil you're using but I hope it meets the GM spec and is from a major oil company.

mistermog

That could be the guide issue, but what about the valve head?

I'm so paranoid I only drove my car 1,000 miles last year, gasp.

jschindler

I hope you are kidding - I understand that some folks only have so much opportunity to drive their car, but if you truly are paranoid, sell it.

Here is my suggestion to those who are concerned...

1) don't mod you car

2) don't track your car

3) shift at 6500 or below

4) watch your oil temperature and don't run your car hard until it's over 150

5) do not shut the car down until the oil is close to it's normal operating temperature (meaning if you have just run the car hard)

6) keep your oil level near full all the time

NachosZO6

jschindler,

I know your suggestions aren't the end all of valve failure, but it gives me a little more confidence while driving it before I get these valves replaced. Only suggestion I can't follow now is 'do not mod it', too late for that.

mistermog

Yes I am kidding, I drove 1400 miles. Not because of the valves, just because she's a garage queen right now. (work commute not vette-friendly, I put 173k on a 2000 c5 doing it).

I drive it from time to time, but I really would like to solve the valves/guides issues though. Just waiting to see a solution. The stock valves bronze guides idea w/ roller rockers might be a good solution, if in fact that is something that SOME company here is researching. I just need to find somethign that I know will work without any sacrifices.

In the mean time, I'll lurk in all the valve threads.

jschindler

I truly do believe that those precautions would make a big difference in engine life.

I get that. Mine isn't quite a garage queen in that I make a real effort to drive it, but I don't drive it at all for work.

jimman

For some reason that doesn't make me feel better and I didn't realize 13 sets of tires were that much.

D-Rod

I thought the same as you for a long time. I found comfort that my car was not an '07 since when all this "dropping valve" issue started it was only for a 5 or 6 month production period. Then there came a point when the amount of failures became spread between the years and more common. Now I became a little more concerned. Once I started using oil.....I was VERY concerned. Then when Formatto highly suggested I replace my valves/guides I knew it was time to go shopping.

I agree the % of failures are low. However, look at the percentage of Z06's are driven to 30K miles or so. Yes I know there are cars that have been 100K miles on stock vavles/guides but most of them sit in the garage. The percentage that would matter to me more than valve failure is how many cars are running around with valves/guides that are worn with potential failure. After the posts from the many respected people in this thread, I think we have an undeniable problem that is actually underestimated.

When I was told my stock guides and valves were worn I felt like I won the lottery since I caught it in time. Take this thread for what its worth because its goal was to save engines and not start debate.

A good question I would have for Jason and others that routinely see LS7's.........What percentage of LS7's show signs of wear?

OnPoint

D-Rod,

I think that's a fair question. While Jason mentioned they have seen the issue on LS3, LS7 and LS9 engines, it seems - at least on the CF anyway (and yes, I well understand the limitations of the scope of the CF vs. total production), that actual failure rate of the LS7 appears significantly higher than the LS3 or LS9. The number of reported LS7 failures just lately on CF alone is disturbing.

There aren't likely yet many ZR's with a lot of miles on them. However, there are likely a bunch of LS3s with skads of miles on them.

Which makes me wonder. Both the LS3 and the LS9 (I think this is true as to the LS9) have less rocker arm offset, and have less severe cam lift. I wonder if the reason we're not seeing as many LS3 and LS9 failures has something to do with the less severe rocker offset and lift (and slighter smaller valve face diameter). They may also be wearing their guides, but perhaps the wear is less likely to cause a fatal issue b/c of the less severe forces at play.

Dunno. Like many, I will await Katech or other experts to ultimately publish what they find.

In the meantime, tho, I'm driving my vettes and enjoying the heck out of them.

jschindler

First of all, how do you figure that cars with 100k miles sit in the garage? I'm sure I've taken that comment out of context.

Here is the question for people like me - meaning that my car will never be modded or tracked. I figure the odds are against me having a problem. I'm careful about warming it up etc. Yes, I get the fact that it could happen to me - I don't mean to imply that my head is up my butt.

But from a risk/reward analysis, what should I do? What are my options? The question becomes should I spend $1000 plus to have my heads pulled and install different guides and/or valves as protection against something that might happen, but the odds or low, as opposed to waiting for a $2,000 or $3,000 problem down the road....maybe? Of course there is the risk that I drop a valve and wind up with a much bigger problem.

For someone who tracks their car or puts a different cam in it, then I think it might make sense to go in offensively and spend a little money now to save a potentially worse problem that now has a higher probability of happening.

Mopar Jimmy

Good common sense suggestions for those very concerned about all this. I would add to the list, change your oil very regularly, maybe twice as often as GM recommonds, per the oil life indicator built into the dash.

Do you oil minded guys think that going to a 10W 30 oil vs. 5W 30 oil would help with the potential issues presented in this thread?

jimman

Interesting thought in that the Stag 2 performance cam from GM performance has less lift than the stock cam.

jschindler

Good question - I have wondered something similar - it could go both ways. Maybe it needs a higher rating on the upper end - such as a 10-40. But I know for damn sure that I'm not smart enough to figure that one out.

mistermog

well, my theory is that gm recommends 0-40 in europeland, and thats a pure synth base stock vs our 5 or 10 / 30 that isnt. gotta be worth something right?

Z06LINK

For me, it is more of a concern of if something happens when i'm running hard on a mountain run at max G's in a corner. You scatter a motor on some of the roads we run and you just might be writing off the whole car or have it catch fire and burn to the ground. It's worth it to me to spending some money up front, and while i'm at it might as well forge the bottom end and drop in a cam.




run a

AirBusPilot

GM spec oil is clearly failing (or at a minimum, doing nothing to help) in this part of the engine. If GM can't figure out how to develop an engine without it having excessive wear in the guides, I start to doubt their ability to spec an oil. Continuing to use it would be the definition of insanity.

I use a Group 5 oil with a TON of anti wear additives. It also performs extremely well in very hot conditions. It's far better than the oil recommended by GM without question.

Is it the solution? I don't know. At least not yet.

jschindler

I do the same (meaning run some high G's on the street). But I really am not concerned about that issue in my 09. That problem seems to have been fixed with the bigger tank - at least for anything we might see on the street on street tires. That's my story and I'm sticking to it.

BSSN

It's nice to see that my original observations of over a year ago are now being taken seriously.

Anyway, I gambled on it and bought the car with a warranty know I wouldn't keep this one forever, so it's not the greatest concern, but Jason, do you think that the 2011's with the different oil cooler that allows oil temps to mirror coolant temps in normal driving will help? I doubt the car will get 10K miles before I sell it, but on the off-chance that it does, what are the things that separate a 100K mile stock LS7 from a blown-up 10K mile stock LS7, and which camp is mine more likely headed for?