When the oil pressure sender on my 83.5 (waterboxer) went south I went
to the dealer to have it changed.  The van at that time had about 50k
miles.  The dealer couldn't do it; it was not the standard 24mm socket. 
It was so big (27 - 30) that there was no way to put anything normal
between it and the push rod tubes.  As everything about the motor is
tight and leak free I have learned to live with an oil pressure light
that never comes on?  
What have I got in there?
Lloyd Perkins     dad@together.com