Noisy hydraulic tappet?

[Flemming Christensen <fl.christensen@get2net.dk>]

Starting the car this morning I noticed a distinct tapping noise from
the cylinder head. I think I it could be a noisy hydraulic tappet. 
The noise disappered again after a couple of minutes when the engine got
warmer.
Besides from this, it's a perfect running '88 MC-1 engine which has done
about 190000km.

Supposing that it's a noisy hydraulic tappet: Could this be due to
normal wear? Any BTDT's?

Could there be any connection to fact that I put Syntec oil (Castrol RS
10W/60) in my engine.?
I've been driving about 200km since the oil change without any noises.
The car is fairly new to me so I don't know what type oil was in there
before, but I noticed a slightly increased oil pressure from about 5.0
bar to about 5.2 bar at cold start. When the engine gets warm the oil
pressure is in the range of 2.0 to 4.5 bar. Both the old and the new oil
filter have anti-drainback valves.


Any thoughts and suggestions greatly appreciated, but please don't start
flaming about oil types ;).

 
Regards and TIA,
Flemming Christensen
Denmark