Finally the Answer We've all Been....
 

Well i do believe the answer i recieved from 2 major valve companies i spoke to today is enough to satisfy me. We ripped apart an '07' today with a windowed block and guess what was found!? Not too tough to answer right. The head of the exaust valve was broke clean off. What i am some what surprised about is that i am 95% sure both heads are fixable!. Anyway on to the answers....

I was so sick of this controversey so i called Ferrea and another major vavle maker to try to get some answers. I won't name the second because of certain circumstances. The answer i got from both of them is that this valve should not have been hollow so close to the head of the valve. What's happening is the exhaust valve is coming out of the guide off the seat WAY TO far. It is unable to control the heat and is destroying the guide which in turn makes it weak and brittle.....wobbleing around is what was stated and popping the head off at the sonic weld. It was said that if the head of the valve was solid farther up into the guide it would have been fine.

So once again, it does seem to be a degree of more then one issue and the outcome were getting but they did say "not sure what the hell GM is doing putting that hollow vavle in a race piece" is beyond them!?? So let the attacks carry on but i am happy knowing the answer which i believe to be true all along. :crazy:

Yea, what the hell GM?! I'm pissed... Want my money back...

Great news, certainly clears up all the confusion and answers all the questions that have been raised.

Onto the next vexing problem!

I totally agree. I believe the valve is the main culprit as far as breaking at the sonic weld causing catostrophic damage. The guides seem to be another problem but I believe its the hollow valve which is the reason that all these motors have blown up (Valve seperates into 2 pieces). I'm def not an expert buy my local tuner seems to believe the same thing...

Glad my motor has SS valves already installed.

Thanks for the info.

I'm glad I went with solid stemmed exhaust valves for my rebuild. :yesnod:

The naysayers will be here shortly to claim that Ferrea and the other major valve maker are just saying that to sell more of their product and GM Engineers never make a design error. My fat heavy SS exhaust valves rev to 7K and haven't failed yet!

Well, Ferrea did sell my engine builder the valves that are currently in my car. Ulterior motive? I doubt it. My valves were replaced back in 2009 before the forum "blew up" with valve controversy. I had the guides checked and replaced as a precaution in late 2011, and there were no signs of wear after running on the Ferrea valves for 12K miles. Hardly scientific, just food for thought.

This failure is not due to ONE part. This is a multi-part failure. You MUST have the guide and the valve working together to get this failure. The arc of the 1.8:1 rockers starts the process, the characteristics of the guide material "adapt" to the rockers, and the valve transfers heat to help "adapt" the guides....Once adapted, the weak area around the valve head weld gives up the game.

I believe solid stem valves in the FACTORY guides will also wear the guides badly, but they may not give up the game since a solid stem valve is not welded by definition.

Precisely why I changed the guides. Better to be safe than sorry.

I totally agree thats its just not one thing but a multiple of the above but wouldn't it make just common sense to get that damn cheap ass valve out and eliminate most of the root cause?? Not saying SS is the answer either and not pushing it.... but it sure does work :thumbs:

Hahaha, i know.... surprised so far but they will be in here soon :hide:

So then how do you explain the highly prevalent guide wear we've seen, and associated with valve damage?

And then how do you explain the guide wear on the intake side?

Just because the valve may be seen as an inferior design by valve companies does NOT mean it's the actual cause of the issues seen so far. The valve shearing off at the head may simply be a side-effect of another primary cause (like guide bores out of spec, heat dissipation, seat concentricity, etc etc ad nauseum).

If I call up Michelin and Hoosier, I'll bet they have plenty of choice things to say about Goodyear runflats too. Doesn't mean the Goodyears are going to blow out under standard use or otherwise not work as designed... :D

Very interesting information you got from Ferrea, who can sell you just about any valve they want.

Hopefully, the information you got, will put some of the talk to rest.

Others with an agenda which centers around advancing the idea that the stock hollow stemmed valves not being at any fault in the LS7 valve train issu, are liable to argue with you and call you a liar though.

Look for those who either have not done anything with their own heads to show up moaning, or those who have done something with their own heads, but kept the stock valves, to start whining.

At any rate, thanks for the information.

I see the only way you will believe anything is if GM comes in and states the cause. I'm sorry but it ain't happenin' jack. Take the information for what it's worth but like i said above, it is multiple things causing it but he made sure that "heat" was the factor in destroying the valves and making them brittle and also for destroying the guide. Also it does show why the cammed motors seem to pop more because of the valve opening farther down the stem then it should and creating more heat and less stability :yesnod:

Your heads are off the car, at this point why would you keep anything OEM?

Random84 is here to save the day for GM. :rofl:

Pretty good analysis. My apologies if my praise is viewed as toxic :D

A solid stem valve can be welded, but I think the current trend is to one piece forgings or extrusions (I'm not an expert on the exact methodology, but have read that they are weakest at the transition from stem to head, even if one piece). Of course they still can and do break off at the head, but no one is going to want to hear that.

Lastly, even if the solid stem valve wears on the guide, since it is running much cooler than a sodium valve at that point it seems a safe conclusion that such wear will not be as detrimental to the guide. Also once a solid valve 'wears in' the guide and finds a comfortable spot, it will probably be fine and the guide may not wear all that much more, just as we often see on the LS7 intake. depending on the validity of the hypothesis regarding deteriorating/self-destructing sintered iron guides once wear begins. However, put the sodium valve in the same spot -- with a guide worn to comfortable clearance (whatever amount of clearance that may be) -- and the sodium valve will now overheat since the clearance is too great, and will cause more grief to the guide or simply overheat and lose its head. Of course the lesson there is to keep an eye on guide clearance and not let it become excessive.

Too bad you didn't check this story out before posting it since it really, really makes no sense at all; I am at a loss to explain how you got the same silly story from two different sources.

Anyway, if one understands the theory of how a sodium valve works, then one knows that the sodium cavity must extend to the head of the valve, because that's where the heat is -- the head receives the heat of combustion. If the sodium cavity did not extend below the bottom of the guide, the sodium would get very little heat to transfer up the stem, so what would be the point of the sodium?

For those who couldn't figure it out on there own and still don't get it after reading it, let's look at an image of a Manley NexTek sodium valve that has been posted here several times before, while keeping in mind that this is not the valve used in the LS7:


The dashed line on the sodium valve -- the one on the left -- depicts what? Yes, that's right -- it depicts the hollow area of the valve, right down to the head. That's. How. Sodium. Valves. Work.

There are other images of other brands of sodium valves that show the same thing -- the cavity goes all the way to the head. Because. That's. How. Sodium. Valves. Work.

good info, thank you. :thumbs:

Thanks for the info. I hope this is correct. :thumbs:

:cheers:
DH