forg0tmypen

I've seen very compelling arguments as to why you should and shouldn't switch out the OEM valves in favor of stainless steel valves. On one hand, you have people saying the SS valves are stronger, and less likely to break than the very thin walled OEM sodium valves, but then you have people like Jason at Katech saying there is nothing wrong with the OEM valves. I tend to agree with Jason, but its hard to argue that the SS valves are a lot more durable. I wanted to start this thread to pick back up discussion on this topic as I want to make the right decision of what valves to use when it comes time to freshen up my LS7.

Senator Carbon

From all of the reading and old time thermodynamics that my brain remembers, it seems to me that we do not have a "valve" problem, but a possible "valve guide" problem. I think that is what Jason is pointing to.

Inquiring minds want, or should I say NEED, to know.

forg0tmypen

Yea, makes sense, but wouldn't a stronger valve hold up better to the stresses put on it by the wear from the guides?

Mopar Jimmy

Jason at Katech has come out and said repeatedly their is nothing wrong with the oem sodium filled valves and that is what they use on ALL OF THEIR ENGINE BUILDS!!

That's all I need to hear from the Shop that builds countless LS7 High Performance Engines and Racing Engines for GM Racing, and also runs them in their own personal Zs (the oem sodium filled valves). Also, their have been no issues with the sodium filled valves in the battle tested LS6 engine.

That's not good enough for you?

Remember the old expression, if it's NOT BROKE, don't fix it, if you must pull your heads off and get them more bullet proof in your mind put on some bronze valve guides, new oem valve springs, and call it a day and enjoy your car.

forg0tmypen

That's what I'm leaning towards The reason for this post is because Ive talked with Rich at WCCH and Jeremy Formatto owner of Fasterproms and both have told me otherwise, that a stronger valve is a better alternative to the "weak" and "thin" sodium valves. I'm starting to think that both will work and both are durable and will last. In the back of my mind however, I keep thinking that a stronger valve will better withstand the wear and tear of this engine. Hence this thread. Thanks for the input Jimmy.

Mopar Jimmy

Mr. Gizmo

Interesting Commentary from the LS1tech forum.

I am inclined to go with the solid SS valves versus the sodium filled, when I decide to go through the top end. I think this is a definite must do for any cammed Z or a Z with over 20k miles.

http://www.ls1tech.com/forums/genera...-problems.html

The commentary on the LS1 tech forum seems to think that the sodium filled don't dissipate the heat and become brittle. I tend to think the design engineers got the "CHARLIE TUNA syndrome" going when they decided to use Sodium filled. - Sodium filled sounds technologically advanced and superior - and any performance gain is so miniscule that it does not offset potential catastrophic failure.

forg0tmypen

Man, this is tough. Good arguments on both sides. Ive now read that Sodium valves transfer too much heat to the guides, whereas SS do not...

tjwong

No one really knows the true cause of the failures. Jason at Katech mentioned they are investigating the causes, is it really guide wear that causes head separation? Well IMHO I say now, others say yes. But I can say that I just saw a LS7 head at a machine shop that had so much wear in the guide that the valve wasn't even seating properly anymore. I can tell you that the valve had at least .030" of movement from side to side when I had the exhaust valve about a half inch off the seat. If it was excessive guide wear that would cause the valve to fail, then this would have been the one head where heads would have been falling off. In fact in this one head I inspected three of the guides were worn that much, the fourth was about .020 or there abouts.

GM uses sodium filled valves to lighten up the valve train so that the LS7 can run at the engine speeds that it does. The sodium filled valve stems also transfers heat better as well to control the amount of damaging heat to the valve. On the downside of things, if the chamber temps escalate and the stems transfers a lot more heat, then the oil that is in the guides will "coke" and will cause more wear because its no longer providing lubrication but rather causing problems because the oil has carbonized. Escalate the temperatures more and now the sodium turns from a liquid to a gas, now the valve stem will no longer transfer heat as it did when the sodium was in liquid form. Now you have a problem because the valve is getting excessively hot and if hot enough it will fail, meaning head separation.

GM also runs the engine on the rich side of things to keep the chamber temperatures down. Lean the PE AFR up a point or so and your chamber temperatures will escalate considerably, and also the exhaust valve temps will rise drastically. One can say its this or that, but so far there is no definitive answer. Just my two bits worth.

OnPoint

They use Inconel exhaust valves on their higher horsepower builds - on engines with redlines of 7000 rpm.

Mopar Jimmy

On their (Katech) basic heads and cam uprgrades on LS7 engine making the typcial big heads/cam LS7 power (up to 600 rwhp) and on their Street Attack package, they use the stock sodium fillled valves.

So do the following very well respected Vendors that I know of for certain on their high performance heads/cam build ups, who have all gone on record that they are not seeing the "Sky is Falling Down issues" as a problem with the LS7 engine.

ECS
LGM
Livernois Motorsports


That's all I need to know concerning the issue of valves discussed herein.

OnPoint

True. They reserve the Inconel valves for the really big power applications. Along with bronze guides. And indicate a 7000 rpm red line (which indicates they seem to spin up just fine).

BLW BY

I thought the sodium filled exhaust valves were the cat's meow.
Dissipate heat to the stem cool it with oil and it's lighter.

Please take mine out, I can't stand it any longer.

Regardless to popular belief, GM is running these motors at about 95%.
True you can get another 5% and not give up much on reliability but any more than that is a trade off with reliability. That's like 25 HP. Take that to 50 HP and now you're playing reliability roulette with your $12,000.00 motor. What's gets me is that you have to pay for it. LOL
Do see the risk factor and it's exponential.

That is why you have competent motor builders, like Katech, have no issues with them.

Detonation is a terrible thing

forg0tmypen

Well, I started this thread to compare the pros and cons of each. True, Katech uses OEM exhaust valves, I'm just playing devils advocate so when it comes time to tell my engine builder I want you to do "this, this, and this" I'll make the best decision. I'm just trying to make my engine more reliable, not anymore powerful

TORQJNKY

In to follow more discussions. I have a new set of Ferrea SS exhaust valves and bronze guides sitting on my work bench. Decisions, decisions.

MTPZ06

Yes, but it still doesn't cure the issue. Once the guide has excessive wear, the valve begins to seat improperly. Regardless of what type of valves, the excessive guide wear will eventually cause an issue.

Still wonder if it's a geometry issue, rather than a materials issues. Makes me wonder why GM chose to go from 1.7 rockers in the LS6 to 1.8 rockers in the LS7, when they could have just put more lift in the cam?

forg0tmypen

I think the 1.8 rockers are ok and won't hurt anything as long as the geometry is solid. So you're saying that even a SS valve will fail eventually due to the excessive wear?

MTPZ06

Could bend instead of break like the two piece stockers when it begins to seat improperly...but I think it would take more excessive guide wear for the SS valve to fail. Again though, the goal is to have no failure (within reason)...so I want to know what is causing the excessive guide wear.

'06 Quicksilver Z06

How many miles were on it TJ?

Michael_D

Why not run Titanium exhaust valves? Other than cost that is...