Ben:
Real common in 2.0l air cooled buses and Porsche 914 2.0l engines with
the 3 bolt heads.  I have one of the Porsche 2.0l engines, but the heads
will be gone through and all the valve seats replaces by shops that know
this problem and fix it.  Too much money in the 914 engines. I have a
1.8 Porsche engine and they do not have this problem.  All of your
causes are right on. The 2.0 914 engine will just drop a seat for the
fun of it.

Richard

Benny boy wrote:
> I small section on my site, i just began!!!
>
> http://www.benplace.com/valve_seats.htm
>
> Regards, Ben
>
>
>