Ominous knock?

[drummerboyXJR]

Hi, have just bought an XJR V8 that has been standing for several months due to starting problem (electrics, not flooding)
Got it running but it has a nasty knock fron top of engine which seems to come and go while ticking over. Havn't revved it or put it under any load.
All chains and tensioners have been done, this is a knock rather than rattle, anyone got any ideas what it might be?
Am fearing the worst, but am hoping it might be oil not finding its way round yet, due to standing so long?
Any tips would be appreciated.
Thanks