Modified head - what valves do you run? Poll!

[Thuppu]

Quite interesting not more people use 7A valves.

[andrewcoupe]

Interesting Thread, I`m in the process of getting a new valvetrain for my 7A engine.
I had my mind set on Supertech but have heard that the Ferrea is of better quality.
If I`m spending a large amount of money I want to do it properly and do it once.

I`m hoping to rev to 9000 RPM ...

[igor136]

Yes, the risk with old sodium valves are real:

1. Was valve springs OEM or stronger? Maybe too strong.
2. Was OEM exhaust cam? Maybe 7a?
3. This was exhaust valve. That can be overheating, bad fuel/air ratio.

[orignalS60]

I'll be using a stock sized ferrea replacement set.
They look to be stainless. I too have heard of people
snapping stock valves. Quick question for you guys
what brand of valve guides do you recommend for
replacement?

[Thuppu]

1. Was valve springs OEM or stronger? Maybe too strong.
2. Was OEM exhaust cam? Maybe 7a?
3. This was exhaust valve. That can be overheating, bad fuel/air ratio.

1. Stiffer springs, not sure about the brand. Not OEM.
2. Schrick 260/10.9 cams.
3. Yes, exhaust valve. Usually you get a burnt valve(have experienced it twice), but this has snapped off totally and bounched between the head and piston. Did make a hole in the piston.

This was on my friends car from last summer. No idea of the total km driven with the head, but it was serviced before this.

[orignalS60]

My new setup will be ferrea stock sized valves x20,
Supertech dual valve springs & titanium retainers,
Supertech valve stem seals, INA oem lifters, 7a cams,
new timing chain, adjustable cam sprockets, tommi
adjustable cam gear, Febi valve guides if needed.

Does anyone know if ferrea and supertech valves
require different valve locks or are the stock locks
fine?

[blackS2]

1. Stiffer springs, not sure about the brand. Not OEM.
2. Schrick 260/10.9 cams.
3. Yes, exhaust valve. Usually you get a burnt valve(have experienced it twice), but this has snapped off totally and bounched between the head and piston. Did make a hole in the piston.

This was on my friends car from last summer. No idea of the total km driven with the head, but it was serviced before this.

I will try to descibe what may happened in such a case.

If a valve guide is worn, it has a wider diameter at the top and/or the bottom end - like a trumpet (so to speak). When the valve is returning to the valve seat, the valve disc and the valve seat are not 100% concetric. So the valve disc hits the valve seat first at one edge and bounces from one edge to the other until it fits concetric in the seat. Maybe the valve is also forced to bend a little bit in this moment (without bending it actually) (you know what I mean). Over the time the stress to the valve is to big and the result is a fatigue fracture.

I hope I found the right words to describe this in english

here a similar result:

[Bowie69]

That makes good sense, thank you

[Thuppu]

Yes, that makes perfectly sense. Even that the guide work is done the valves can already be tired and just snap at some point.

[JariP]

Also when the valve guide is worn and the valve head is not touching the seat the correct way, the cooling of the valve is not working. Sodium filled valves are cooled about 40% through the valve stem and valve guide and 60% through the valve seat. So with the worn valve guide you get the combination of fatigue stress and over heating. Also with enough heat it is possible to get the sodium inside the valve stem to overheat and actually boiling and then it's game over. I don't know which one usually kills these valves, fatigue stress or lack of cooling, or both of them combined, but I wouldn't simply just blame the valve. The sodium cooled exhaust valves where high tech 20 years ago and they are still up there. Nowadays the hottest **** could be the sodium filled inconel valves which are available from some manufacturers.

Compared to the sodium filled valves the regular solid stem valve is cooled about 20% through the valve guide and 80% through the valve seat. So it should be clear why Audi used or still uses the sodium filled valves, it's all about heat control.

[Thuppu]

Mahle exhaust valve 029 VA 30889 100 http://catalog.mahle-aftermarket.com...&embedded=true

So this isn't sodium filled? Anyhow it says AAN/3B...

[RichLV]

As far as I've researched, only OEM Audi valves are sodium filled. All of the replacement options (Mahle, TRW, etc.) are standard stainless.

[Thuppu]

Thread lift...

If I go with inconel ex-valves do I need to change the guides or is stock ones good to go(if not worn).

[Vorsprung durch Technik]

I would just do backcuts on them, nothing more.

JP is recommending to Swirl polish my new Inconel exhaust valves.I haven't discussed it just taken his word on this. I take it the 30 degree cut back on the exhaust valve is for flow reasons ?yes/no? Would this cause any problem in the longevity of exhaust valves?

[JariP]

Yes and no.