383vett

Detonation will result in harmonics of the valvesprings which will affect their ability to control valve float as well as shorten their life. Valvefloat will destroy valves.

edmundu

From my limited understanding of it, it isn't just the Ti valve, but also the seats that would need to be replaced, along with associated machining/labor work, end result $$$$.

mirage2991

Of course but you made a general statment, and we are under presumption that we are talking stock engine, no exotic NASCAR or pro stock and definitely not 9500 Rpms. At our level, ss and a good spring would do just fine, if one would so choose to go that route, as they have been fine for many years.

Jasil

Definitely...... and I don't think anyone is disagreeing with your statements either. The fact remains welded multi piece valve is not as strong as solid SS valves. When changing to SS a better spring makes 7K shifts a breeze and gives a ton of piece of mind over the factory piece. Remember if that welded valve fails you are out 10K+ not chump change.

I'm waiting for 25K miles to swap mine, but I will be swapping to SS valves, bronze guides, and a better spring 7K all day long is not a problem imo and I will not have to wonder will I be a victim

4MuscleMachines

So then what are the best options for the lightest one piece exhaust valve for street cars?

bullitt4110

Thanks the info and opinions. Pretty much backed up the way I felt. Ryne what springs do you run with your set-ups?

Michael_D

That makes no difference. Theory remains the same, and that is what I said. A lighter valve is easier to control. Adding weight will reduce redline capability. If you are OK with loosing 500 rpm, go for it. I am not. Also, increasing spring rate can induce instability, not allways reduce it. Without spin tron analysis to verify, you are just guessing.

I hate to burst your bubble, that is not a fact. Two piece valves are generally more robust than a solid valve. Most solid 1 piece valves start out as a CAST blank, then they are machined. Welded valves start out as solid forgings, then they are machined, then joined through fusion welding. The grain structure at the weld area is generally superior.

OnPoint

Interesting.

I did not know that.

VetteVinnie

And so are you. Make no mistake about it. You have zero empirical evidence to back up your claim of a 500rpm drop in redline. Mine redlines at over 7K rpm just fine, thank you.

Unreal

Maybe it is a case that good springs on a stock valve could go 8500rpm without issues, good springs on a SS valve go 8k without issues, so if you going to 7k it doesn't really matter. No one knows or has tested it so who knows?

Lawdogg

I think we just may have the winning thought.

vertC6

Hey Micheal,

This is all very true but you are leaving out the most important part...

I had a chance to talk with the gentleman at Del West that you spoke about and I also spoke with Ferrea. They both agreed that race teams were using the sodium filled valves because they are a cheap alternative to Ti. BUT they then scrap the valves after X amount of events. The valves were never made to last because they get weak and eventually break, they both confirmed this to me.

One of the engineers at Ferrea said that the stock LS7 stem was about .038 thick (very thin) as it heats up the sodium will liquify and does a great job at disapating the heat, but over time with the extreme temp changes it will weakin and eventually break. Richard at WCCH has confirmed many of the guides and valves that he sees have a BBQed look to them.

If you read the Ferrari forums you will see the same thing with the old 308's, they sound just like we do on this forum about the sodium filled. It has become clear to me that this is not a new problem but one that has been going on for a while now.

Ferrea is coming out with a "non sodium filled" hollow stem SS valve that the stems will be around .080 thick and will weigh in around 85 grams (only 7 more that the Ti intake).

One thing that I don't think many take into account when it come to the exhaust valve weight is it's relation to the weight and pure size of the intake valve. The 2.20 intake weighs 7 more grams than the sodium filled exhaust. On a spintron you are going to loose control of the intake sooner than the exhaust valve. Jason said on their spintron testing with the torquer cam maintained valve stability up to 7800, but he never confirmed with me if it was the intake or the exhaust valve that bounced first. My feeling is that the intake would bounce first even with less duration and lift because of it's size.

I say all that to say if you add 15 grams to the much smaller exhaust valve I don't feel that reving into the lower 7000s would be any problem at all, and I will sleep much better at night knowing the Ferrea hollow stems are in my heads.

Michael_D

Yes I do, it's called math. An additional 20 grams is actually closer to 600 rpm at 7K. You're welcome.

VetteVinnie

Prove that the SS valves cannot sustain the stock redline. Otherwise it is conjecture. You are making the assumption that the factory redline is the maximum that the stock valves can withstand.

You're welcome.

vertC6

If the Katech cam can sustain 7800 I would "assume" (I don't have proof) that the factory cam should do at least that.

95jersey

Not that it proves any point, but the GT3 Z06's used in European FIA GT3 competition raised their rev limit by 200 rpm's with no internal modifications. The Z06R went on to claim wins and propelled Callaway Corvette to claim the first series title win for the car: the 2007 FIA GT3 Team Champion and the 2008 FIA GT3 Drivers Champion. In 2009 it won the German ADAC GT Master manufacturer Team Championship and the 2010 FIA GT3 Drivers Championship.

General
- GT racing car based on FIA GT3 regulations (not road legal)
- Front mounted longitudinal V 8 engine with 6 speed rear trans-axle and rear wheel drive
- Car has standard Corvette Z06 components unless otherwise stated
- Optional passenger seat installation

Engine
- Standard LS7 V8 engine mapped for 98 octane unleaded fuel
- Standard Dry sump
- EFI engine management system
- Manuel throttle actuation
- Motor sport Engine wiring loom
- Stainless steel 2-2 and 2-1 headers, crossover pipe, exhaust manifolds with straight through rear exit exhausts
- Optional silencers available
- Power output 377 kw @ 6300 rpm
- Torque output 600 Nm @ 5500 rpm
- Max engine rpm 7200
- 515 bhp

VetteVinnie

But there are several other components in the engine aside from the valves themselves to consider when determining maximum RPM. Unless someone proves otherwise with empircal data that the valves themselves (and the springs, which are also upgraded in most if not all SS valve conversions) are the limiting factor, then it's pure conjecture that the SS valves cannot withstand the stock rpm.

I seriously doubt Michael_D has a Spintron to prove or disprove his "theory". I don't care how good your "math" is, you cannot have a definitive solution with a unknown variable; you can only have a range of values. Now if Jason at Katech comes in and shows Spintron data indicating that the various SS valve/spring combos no matter what cannot withstand the RPM limits imposed by the factory redline, only then will there be enough empirical data on which to deduce reliability (or lack thereof).

Michael_D

No, that is not what I have said. I said that redline capabilities will be reduced when adding weight. I'm a bit vexed that some of you are arguing with me over that point....

Katech has already conducted spin tron analysis on the OEM valve train, there is no need for me to do the same, and I am not making an assumption, as you put it. It's already been proven.

Extreme fuel cut off in a stock 07 Z06 tune is 7200 rpm with the extreme resume of 7120 rpm. I have personally seen 7600 rpm on a missed 2 > 3 up shift, with OEM components. On a missed downshift, fuel cut off will not prevent over rev. I want the head room for both. You may not. It is a personal choice.

It is also conjecture that a heavier valve, with aftermarket springs and cam will remain stable above OE redline without spin tron data. Prove to me that an extra 20 grams, with the springs and cam of your choosing, remains stable at 7600. Hell, show me any controlled analysis of any aftermarket LS7 valve train combination for that matter. I'd be curious to see it.

Just for a tidbit of info, David Vizard's latest head porting book does have a side bar on post spin tron analysis on valve weight and rpm capabilities. Three valves with the same spring, retainers and locks. 119 Gr solid stem - 7600 rpm. 101 Gr hollow stem - 8000 rpm. 89 Gr Ti - 8300 rpm.

VetteVinnie

Again, prove that it's the valvetrain that imposed the factory RPM limit. Are you suggesting that it is improbable that other components could have contributed? Pistons, perhaps?

Yes, it is conjecture regarding the SS valves. No question, especially since there are other variables (different valve manufacturers, different springs, different cams, not to mention variance in tolerance with ANY mass produced component). But I am tired of people saying that by adding the SS valves, you reduced your engine reliability or sacrificed your factory redline when they have absolutely no empirical data to back up those claims.

Now if I drop a valve and detonate my engine and that failure is traced to the valve itself, you will be the first on my notification list.

H82BFST

I'm sure it does. And hopefully the valvetrain is still stable but behind the wheel you likely wouldn't notice. And anyone who has every driven a Z has also over reved one. Most will agree right? Hopefully that 'window' of safety of valvetrain stability over 7200 rpm is still available with the heavier valvetrain.

So, all this brings back memories to good ole LS1 days. The LS1 pistons didn't have valve reliefs and guys were smacking them left and right and bending push rods. They would swap them out with aftermarket hardened push rods because the 'stock' push rods were weak and caused failures. Oh so much fun reading... haha later so many photos of 'notched' pistons, bent valves, busted motors from failed valves, etc. Different time, different forum, gotta love history.

While I will eventually have my LS7 heads modified, it won't be by ADDING valvetrain weight. (At least I am not convinced by these non technical buyerner threads at this time.) ESPECIALLY on an awesome motor like the LS7 with a factory 7200rpm rev range. In every LS engine I've had, I've done what I could to REDUCE weight in the valvetrain, etc.

I'm more interested in what the vendors have to say about piston to valve clearances, the stock LS7 spring capability and what single spring replacement they would recommend for a little more stability and perhaps a mild cam, etc. Also, aftermarket base circle differences and geometry changes, pushrod length adjustment, etc. Where can I find these discussions on the LS7 instead of sale threads and these type of arguments? I want the technical question answered of WHY GM would spend the extra R&D, MONEY, etc on exotic valves if they could have simply used SS valve and it still all work the same without issue. Engineers have to FIGHT REALLY hard to a more expensive exotic part pass the bean counter test if it isn't NEEDED. Point me to the tech please.