[ROVERNET - UK] Head scratches and piston numbers

[Gavin.Walker at csiro.au]

Hi Everyone,
  Spent most of Saturday decoking the SD1 engine.  It was really hard
work.  The oven cleaner certainly helped, in combination with a brass
wire brush, scourer, chunks of formica as scrapers and a scourer pad on
the end of my drill.  The head I got back from the shop replacing the
valve guide was mostly clean to start with.  I wish I had access to
their dipping tank.  All they were interested in was a full service for
$400.

The heads show signs of being fiddled with.  Material has been removed
from a passage ways and the chambers.  Doesn't look like a professional
job though.  I couldn't get all the coke out of the passageways but I'm
mostly happy.  The head I sent to the shop has come back with a few
scores on it.  They not large but are deep enough to catch my finger
nail (The join the middle two chambers).  I don't expect I can do
anything about it.

Three of the pistons had "kisses" from the valves.  I lightly sanded the
marks to remove any sharp edges.  The pistons have "FRONT" and 030
stamped on the rim.  All the front signs face the front of the engine
and I assume 030 is 30thou oversize.  All the pistons have a "6" stamped
in the middle.  Anyone know what that means (I suppose it could also be
a 9)?

I cleaned up the valves and lapped them in.  To clean the valves I found
it most effective to mount them in a drill and lay in to the surfaces
with an old chisel, followed by 80 grit and them 800 grit.

On the whole, a successful weekend.  Reassembly starts next weekend.

Gavin Walker
Canberra, Australia