Hi guys. I've looked through a bunch of old threads to see what the concensus is regarding the quality of the stock valves. From what I can tell, there isn't one. Some prefer the stock valves and others prefer aftermarket, non sodium filled valves. The threads I found were all from 2003 - 2005. Now that you guys have a few more years under your belt w/ these valves, what is your opinion? What are the pro's and cons of each?

I am prepping a pair of 2 valve heads for turbo use @ 12psi.

Thanks

 

If you are fully prepping the head's its well worth converting to chev valves lighter cheaper.bigger heads ..
The price of factory valves is just ridicules.
I like titanium valves my self second hand Nascar ones are not so steep People seem to think ti valves don't last as long but thats always in aplications where the cam profiles are hammer time ...in Porsche the cam profiles are so small and gentle I reaaly don't think it would be an issue .. just look at the recomended spring tensions there are at least double for most chev applications and they are calculated from the cam ramps ..

 

In theory, sodium-filled valves are the best type to have for sustained high combustion temperatures (like running under boost for long periods on the Autobahn or something) because the liquefied sodium can transfer the heat best. In practice...if you can use lighter, solid valves without burning them, go for it. Reducing reciprocating mass in the valvetrain is always a good thing.

 

Are there any inherent problems with the stock sodium filled valves? Other than the weight penalty and cost?

 

If you are going to run on the track at sustained high boost, use the sodium-filled valves. I have seen the low cross-section valves burned away on track cars.

 

No track plans for this car, just street use. I like the idea of factory proven parts, thats why I was planning on upgrading to the 951 valves. They are 2mm bigger than the stock valves in the U.S. 2v 928 heads and the exhaust valves are sodium filled for a reason. Since this car is turbo charged, I'm following the proven path set forth by my 951 brethren. I just wanted to make sure that something better hadn't come along. I know there are plenty of valves available in the aftermarket that are undercut and offer a weight savings but I have been unsuccesfull finding them sodium filled. Those are pretty scarce in the aftermarket as far as I can tell. Or maybe I'm looking in the wrong places.

Thanks

 

Friend did 30k miles (road + half a dozen track days) with aftermarket, non sodium-filled exhaust valves, after which valve guides were as loose as guides that would have done three times the same mileage with original sodium-filled valves.

 

Well, that settles it. Thanks guys.

Now where is the cheapest place to buy stock valves, seats, stems and seals?

 

Stay with the stock sodium filled exhaust valves. You can make plenty of power with them and unless you have a top end setup that supports HP in rpm ranges over 7100 rpms, there's no reason to trade the extra heat capabilities of the sodium valve for something lighter and solid (non sodium filled).

TonyG

 

I've done a little more research and found that TRW was the original supplier for the exhaust valves for the 951. These parts are $125 - $150 each. WTF??? I have also found Federal Mogol AE ( which is FM's OE valve division ) for about $40 each. Pelican sells a brand called Intervalve for $48 each. Do any of you have experience with the FM AE valves or the Intervalve brand? I really can't justify paying $125 per valve. Thats rediculous. I have twice as many of these things to buy than you guys.

 

Heck for that price you could buy a pair of turbo heads and take them apart!

 

How come you guys don't use inconel ex valves?

 

People may not say it, but that's actually the reason that so many guys use different valves, in our community. Someone suggested buying some good 951 heads. That's the right answer.

 

I have heard that too much sodium causes high blood pressure….must have something to do with the price!!

The main reason most folks go with non sodium valves is that they wanted larger valves – and you don’t get a choice then! The stock sodium valves are quite hardy and good used ones are easy to find and recondition.

BTW – the valve stem OD of the stock valves is very uncommon….you can’t get larger valves with the stock stem diameter without going to a custom valve.

 

Thanks Chris. Have you ever used the Federal Mogol AE brand valves? How about the Intervalve brand? Those valves are about 1/3 of the price of the TRW valves. Is that huge price difference justified?

Thanks for all of the input so far guys.