So here's another question then...

Replacing standard WRX exhaust valves for Supertech Inconel jobs is almost a no-brainer if the WRX ones would need recutting. But what if my valvetrain were an STi3/4 with similar wear, just for argument's sake. Would I be better off replacing the worn STi sodium-filled valves with new OE replacements or would the Inconel still be the best choice?

Just trying to get a feel for all the options here.

 

So swapping worn WRX valves for Inconel would seem a no-brainer. But what about if it were an STi3/4 valvetrain with the same kind of wear to most of the STI sodium filled exhaust valves - better to recut them/replace with OE, or still go with the Inconel?

 

Just looked at the pics on your project page. I had (wrongly) assumed these were V4 sti heads, as STI4 heads were mentioned on this thread. ANyway, the SUpertech valves would be a worthwhile upgrade over UK valves, and cost about the same as new OE or many factor valves, new STI valves cost £49.50+vat EACH!

 

Well they are the two options that are before me at the moment. I have a pair of WRX/UK version 4 heads, and I will have an STi4 valvetrain on its way to me, but haven't done a close inspection of the valves yet, so can't tell if any will need replacing. Hence my question about whether the Supertech were a better choice than the STi ones, if the STi ones needed replacing.

As you say, the new STi valves costs a fortune, so a full replacement of all 8 would be out of the question. But there would be a 'equal cost point' where it might be a straight choice - replace a handful of ex valves for the exact same new STi ones, OR replace the whole set for your Supertech Inconel? I.e. leaving cost out of it, which are 'better' valves - STi sodium filled or Supertech Inconel?

 

Zen Time Attack car, Inconel. RCMS time attack car, inconel. Prodrive WRC impreza, inconel.

The sodium core of the STI valve does offer more valve cooling, but the heads seem to wear very easy, and snapping off isn't unknown, i've never had a engine respond badly when swapping from sti to supertech valves (in terms of mapping, power etc), and the supertech inconel valves are VERY robust.

 

That's all I need to know Paul, cheers. What do you think of the standard Supertech inlet valves, the black nitrided ones. They seem to be undercut on the stem so presumably flow better than standard valves? A worthwhile mod to build the 'ultimate' street and track head?

On another note, it always seems weird to me that my old Clio 16v had underpiston oil sprays and sodium filled valves, yet a standard WRX doesn't. Maybe Renault were more into over-engineering in the early 90s.