I too have seen the "heili-coil" nuts you describe and they do seem to work
well over the years.
I have used the 12mm copper nuts as well.

I recently on my last two wbx rebuilds have switched to using some 8mm all
thread in stainless steel with stainless lock washers and stainless nuts. I
cutt the all thread to length and insert it into the head and use the
stainless hardware with never seize and so far it seems to be working well.
I recently had to replace the cat for smog and it was nice to not have to
deal with the usual rusted frozen hardware.

Stainless seems to work well.

Doug

----- Original Message -----
From: "Jonathan Farrugia" <jfarrugi@UMICH.EDU>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, August 12, 2004 3:20 AM
Subject: exhaust nuts

> so a week or so ago i had the chance to take apart a 1.9 wasserboxer
> exhaust with the factory exhaust system on it.  or i assume it was since
> the van is from arizona.  anyhow the exhaust nuts mounting the headers to
> the heads were unlike any that i have seen before.  they are 13mm nuts
> with what look like wound spring steel inserts inside them.  similar to
> what a helicoil looks like.  if these are factory nuts are they still
> available at the dealer or would the dealer hand me some regular nuts with
> a N part number?  additionally does anyone know why these nuts were made
> like this?  i would guess something to do with the thermal expansion
> differences between the aluminum head and the steel of the header and
> stud.
>
> jonathan