I think you sent that to my old account I'm the one with his head

I didn't understand what you said:

So let me try again:

a) you have a broken valve with no signs of wear (coking, whatever) on the stem, or

b) you have a broken valve that came out of a guide known to have no guide wear?

I can post a wiggle text on 505's head if need be. when he shipped me the head they had some things on them that only 505 would know. to rockers had the tips cut off and the rockers bolts rounded off in two rocker arms. the two rockers are still on the head.

No sir, I do not believe a failed guide is the only way a valve fails. I believe it is the most common cause from how I interpret the data we have available. At some point in a modest volume car I know that an OEM will have a failure of just about every part of their car; water pumps, trans, door handles, radios, ac, you name it...and there will be a valve failure. That would be pretty ignorant for anyone to think along those lines.

Would folks agree that 9 out of 10 cars on this forum have guides out of spec when measured? Why then, aren't we seeing 9 out of 10 cars fail valves, and 1 out of 10 cars have guides out of spec?

There are the additional factors supporting my personal take here, like Katech's 100% track record using OEM valves in customer motors that cost $40,000+. The employees there put a roof over their head and food on the table for their families by selling LS7s, if they really saw an issue with the valve rather than just the guide, they would not use it. Plus, any WCCH head with bronze guide and OEM valves has proven 100% successful as well. If that's a sample of 50 and SS is a sample of 220, they are both small I admit, but they are successes thus far nonetheless. So that sample of 270 no longer having factory guides regardless of valve type has a 100% success rate in my opinion.

I don't know what the tolerances are as far as how out of spec guides can be where the oem valve still survives. Hoefi had some great insight here, maybe he can chime in. I say the OEM spec limit for guides is the limit, because I haven't observed any data point to counter this. No doubt a SS valve will fare better with an out of spec guide causing repeated off-centered head hits and stem wear. But that isn't the discussion. The question is (at least for me), why is it necessary when I only see failures on out of spec guides, and why is the guide failing so often? The machining theory for all years (not limited to 09s /10s etc) is the only one I can't poke a hole in with the data. Again, my theory/perspective here, want to make that clear.

Sorry, but your part in bold is incorrect. Katech DOES NOT have 100% track record with the stock exhaust valves as you say :smash:

You refer to the one in Germany?? Shame on you ...

As usuual I read your posts with great interest my friend.

First because they are well thought out, well written, and you tend to make several good points in each post you write.

Finally, even though you and I have gone different routes in the management of this matter, I have the utmost respect for you, in that you have consistently put your money where you mouth is.

You, (and a few others for that matter) believe in your method and are willing to put it to the test, and under penalty of possible failure and out of pocket expense.

It is difficult for me to describe how much I respect that.

That is considerably more than I can say for some of the other folk in here, and what extent they have gone to. Or not.

So in light of that, here are my thoughts on what you just said.

I mentioned earlier that people refer to mine, as the "shotgun" approach, and I am not offended by this moniker, because they are not too far off in that opinion.

People HAVE had success just doing the guides and keeping the stock valves.

I won't sit here and try and deny the obvious and easily verifiable, because there is no denying it, and my credibility in here, means something to me.

I would point out, that by changing to a more durable solid stainless steel valve, that I am addressing another potential failure point.

And should my guides, someday find their way out of spec, that I have a bit more "forgiveness" in terms of the potential for ultimately a valve failure.

If I can do this, with no practical, perceivable or consistently measurable performance or street penalty, well then it is worth it to me to have that added insurance.

It boils down to this ConfusedGarage. For me, knowing that the stock valves well could be one of the "root causes" or "major players" in this matter, it is just not worth the risk of my running the stock valves, if the penalty for getting rid of them is not going to be severe. And so far, and since late 2005 when LG Motorsports first started using these valves in stock LS7 heads, it has not.

:iagree::thumbs:

:lol:

Oh, that one doesn't count?? Ok, i will find the other ones then....

For clarity, you bought the car with the engine already destroyed? Or did you sell the motor?

Just trying to understand the circumstances as this is 'your Z06' but the 'owner' was tracking it.

He bought it with the engine down already...

I bought the car as a roller. The motor was already blown by the previous owner. I am now the new owner and i had a brand new LS7 with head work, cam and full bolt ons installed by Doug Rippie Motorsports. The car is also for sale.

Thanks. I figured it was something like that, but wanted to understand the story with a little more clarity.

Damn.

Some poor bastard had to sell this car as a roller because of a dropped valve.

The bath he must have taken.

And yet we have folks in here, with no experience in this matter, and never having reached redline in their own cars, telling us how it ought be managed, and feeling that what they have to say on this issue, ought even be listened to.

Yup i couldnt remember what the original screen name was haha. Can send a link to the sheet you posted up?? do you still have the head??

a) yes i have a valve from the heads that "z0sicktanner" has stated the guides were in spec. The valve that is missing the head has zero coking of oil above the seat line

b) i haven't measured the guides myself, "z0sick" stated the guides were all in spec. looking at the stems i would have deducted this same conclusion without measuring them.

Heaven forbid it was a missed down shift with over rev.

I think a little more research on the original owner would be in order before you come to this conclusion.

Ya, just think he is just ONE of the MANY that we don't know about. The guy probably hasn't a clue that there is even an issue and probably never even been on the net. Oh that's right, the internet is the thing causing the drop valve hype.... not the actual problem :ack:

Got it. Thanks for the followup.

As to the bold portion in b), I wouldn't consider that wise but it's a free country ;)

As to the part in bold, I presume you mean coked oil up inside the guide area; I did not find that to be the case with 8 used exhaust valves that I examined. All came out of worn guides ranging from .0074" to .0141" clearance (bottom). I did find cases of soot far up the stems of some of the valves; I presume that those valves likely came out of the most worn guides (I do not know which of the valves came out of which guides). I have noticed similar soot patterns in other photos posted here and there. All 8 valves, uncleaned, did not measure oversize in the lower guide area (actually they measured from one-half to one-thousandth undersize). Were there an oil buildup in this area (tapered coking), I would have expected them to measure oversize.

One of the rougher stems after a bit of cleanup:



This is the same valve before cleanup: