RE: Ur-Q hydraulic head conversion questions...

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

... I can cite my datapoints ... When I pulled the head from my WX engine
... unknown mileage, but the head removal was a result of a project that
started as an attempt to repair a turbo with leaky seals ... :)  On this
head I had several cylinders that had cracks from valve seat to valve seat
and from valve seat to spark plug hole.  I've also got the MC head I pulled
from my '88 5kCSQA, with about 120K miles ... not the slightest signs of a
crack.  I also have another MC head which has perhaps 70K miles (I forget
now) that has no visible cracks.  

Given Jeff's report about the similarities between the heads (I didn't have
both available simultaneously to do a side to side comparo) could it be that
there was some sort of materials change that reduced the problem?  Could
there be some other design change to the internal passages on the head on
the MC to make the problem less likely?  

One thing that I know is that there is a big difference in the shapes of the
piston crowns on the two engines ... I really doubt that would have anything
to do with this problem though.  

Steve Buchholz
San Jose, CA (USA)

> ----------
> My assumption had been that 5 cyl. heads had a similar migration due to
> the
> reported cracking between the seats of the early Urq. Phil, can you shed
> some light on this? Are the MB motors any less susceptible to cracking
> than
> the earlier WR/WX?
>