AUDI 100 - New Member's Problem

[Max Blyton <Max.Blyton@airservices.gov.au>]

   G,day World!
   
   I am a brand new list member, unfortunately with a problem:
   
   My car is a 1985 Audi 100 CD 5-speed manual, with the 2.3 litre HX 
   injected engine.
   
   
   Problem:  Recently, the commonly-heard valve clatter on start up, usually 
   associated with dry hydraulic valve lifters, became loud and permanent.  
   Removing the valve cover revealed one lifter to be mildly seized in the 
   head.  I am replacing all 10 lifters, but what do I do with the "seized" 
   position in the head, where no lifter will fit easily (for reasons 
   described below)?  Can I gently "hone" the hole with a nylon scouring pad 
   until the tight lifter slips in easily?
   
   
   Bigger problem:  The tight lifter position is on no.3 cylinder, in the 
   centre of the engine, right next to an oil spray orifice.  When I removed 
   the valve cover, I was greeted with several small bits of badly mangled 
   brass, which appear to be the remains of an oil spray jet presumably 
   dislodged from the orifice in the centre of the head, and crushed by the 
   camshaft.  Unfortunately, the local importer's parts microfiche does not 
   list a head of this configuration as ever having been imported into 
   Australia (car was a private import).  Hence, no part number, and I have 
   not been able to obtain a replacement jet.
   
   
   Questions: 1. Can anybody identify this oil spray jet?  There is only one 
   jet in my HX series engine (not 2, as is more common) - located in the 
   centre of the head.  The head hole and spray jet are both approx. 11.5 mm 
   in diameter, the jet being a brass cylinder about 6 mm high, with a 
   smaller "pimple" on top.  A fine hole is drilled vertically through the 
   centre of the device, so oil must spray upwards and mist off the 
   underside of the valve cover (?).
   
        2.  Please, please, where can I get a replacement spray jet?
   
        3.  How essential is this oil spray?  Can I plug the oil hole in the 
            head to maintain engine oil pressure?
   
   I REALLY would appreciate some learned advice here, please.
   
   
   Aside:  In the centre of the camshaft, opposite the oil spray position, 
   is an eccentric, which appears to do nothing.  Can anybody enlighten me 
   as to its purpose?
   
   Hoping for a reply,
   
   Max Blyton
   1985 Audi 100 CD
   AUSTRALIA