atljar

Any news on the Ferrea hollow stem direct replacement LS7 exhaust valves?

I had seen a few comments here and there about their development upcoming

VetteVinnie

I am using Ferrea Super Alloy in mine and have been for over 18K miles so far. With the right spring setup, you don't need hollow stem valves. These valves are used in applications that rev to over 9000 rpm.

http://www.ferrea.com/Ferrea-Super-Alloy-Valves/p34197

Here's the hollow stems, but I only see the intake valve for the LS7:

http://www.ferrea.com/Competition-Ho...m-Valves/c8251

briancb1

I have a solid REV exhaust valve and I was looking into a hollow stem exhaust valve when I was getting my head work done.

I was ready to throw down the cash if it was better but my head guy said it wasn't necessary and wouldn't improve performance over what I had.

Get a good high quality spring that fits your requirements and you should be all good.

lt1z

The Rev valves are lighter.

Mark2009

How much do they weigh?

lt1z

I don't remember exactly but something like 92g vs 108g

Mark2009

What weighs 108g?

vertC6

The Rev solid stem weigh 97 grams, and John at Ferrea said their hollow stems should come in around 90 grams (not a huge difference).

Mark2009

While 7g may not be huge, at those weights it would go a long way towards trying to keep a beehive spring on the head (which would be my goal).

Thanks for the info

Jorday

Why is that your goal? Just curious.

Mark2009

From an engineering point of view it is a better (and lighter) design than a 'stovepipe' dual coil arrangement... at least that's what I've read.

The shortcoming is that it won't work with a heavy valve.

Everything I read about valvetrain dynamics says that lighter is better; of course assuming that 'lighter' can do the job.

tjwong

The guys at Ferrea tells me that their hollow stem exhaust valve will be out after the first of the year. It will be just that hollow without sodium. Its intended use will be for the NA applications it is not meant to be used in high temp applications such as supercharged or turbo apps. For those apps their superalloy valve is the choice. I have several sets of the superalloy valves in use and have never had any issues with them on the road course or other race applications reported to date. One car was a TT car that we build a few years ago, that car is still running that was 'beat" daily by younger college student. It now resides in Dubai where it is still running just fine and is still beat on occasionally by the students uncle

I agree lighter is always better for valve train dynamics. However we are not talking about extreme engine speeds here, most don't of the LS7s here has their 7200 RPM fuel cut in place a few may see 7500. We are not talking about NASCAR engine speeds here where they run 8500 and up for 500 miles nor are we doing F1 or Indy car speeds. The appropriate spring with these heavier valves will work fine.

vertC6

I'll have a better option for you guys very shortly

Mark2009

That may be true, but without extensive testing -- such as that presumably performed by GM on the stock setup -- how will you really know? Float, bounce, etc.

Given such a lack of testing on aftermarket combos, the prudent approach IMHO would be to remain as close as possible to the stock (tested) configuration. Of course if greatly increasing horsepower output that may not be possible.

Mere lack of catastrophic failure is not validation of a design; the first 24 space shuttle launches are evidence of that (the 25th launch was the Challenger).

As to revs, I'd want any changes/substitutions to the OEM components to remain as stable @ 7000 RPM.

Mark2009

ChevyCobb

how short?

vertC6

1-2 weeks

achilds

All that factory testing at GM and there seems to be an issue with the valve stock valve train setup anyway. I agree that most vendors don't have the financial ability or time to do this, but GM didn't do it right either it seems. Personally I would lilke to know what exactly is the root cause before I go sticking different parts in my engine.

Rock36

I'd also like to add part of the reason the 7000rpm redline is significant on the LS7, isn't only because the valve train supports it, but because the camshaft, heads, and intake support the right air flow to make good power all the way to 7K rpm without the torque curve dropping like a rock. Not only that, but still have the grunt, smooth idle, and streetability on the low end.

I agree a heavier valve can work if sprung correctly. For instance, the LS6 in the C5Z06 has hollow stem sodium exhaust valves with a stock 6500rpm redline. The LS3, by comparison, has a 6600 rpm redline and more displacement yet still uses a solid exhaust valve. Which just goes to show, while definitely a factor and important, the valves in the valvetrain aren't the only factor in establishing an engine redline.

Dirty Howie

DH