The heater boxes on my '78 engine are supposed to have flexible
ducting to 2" metal pipes that end just beneath the rear bumper.
When the heater is on, the flap direct warm air to the cockpit and
when off, the warm air goes out the pipes under the rear bumper.

  Without the flexible duct on the driver's side, the heated air
will blow on a fuel line connected to the electric fuel pump. :-(

  I attached some 2" dia. flexible aluminum heater duct and hose
clamps.  Since it gets almost as hot as exhaust I did not use the 
paper covered type for fear of fire.  They deteriorated and split 
within a few weeks. So I set out to find a suitable replacement.

  At a local marine hardware store I found 2" i.d. wire reinforced
rubber hose.  It's used on inboard boat engine exhaust pipes to route 
the exhaust thru the transom.  That solution should solve the problem 
once and for all.  It cost about $9 per foot.

  I'm not sure if that heater box plumbing is common to all late model
air-cooled transporters or not. If VW designed in this system to get 
the heat out I thought I might as well hook it up the right way.
Just what kind of flexible hose was on there from the factory I wonder?

Jack  '73 Westfalia  ('78 engine)
Costa Mesa, CA