Hi, just started to re commission my v8 as has been laid up about 5 years, oil level and visual check looks clean, after about 5 minutes temp at normal but oil pressure drops from 40 to approx 15-20 psi at 800-1000rpm tick over. The engine has only done about 2000 miles since full rebuild, many years ago. Any ideas please on the prime suspect that may cause this
Thanks
Den.

That seems normal to me, what was it when it was rebuilt ?
If you're still using the electric gauge, those can be unreliable.
What is it with a bourbon tube gauge ?
My Jag is quite high, always has been, but I think someone stuck in a very strong spring in the pressure release valve.

Don't recall it dropping below 20+ , wasn't aware that the gauges were iffy, and whoops afraid I don't know what a bourbon gauge is? : Is it a hydraulic gauge and would I need to take my sender out and replace. Sorry if this is a dumb question.
Appreciate your help thanks.

Bourbon tube gauge is mechanical.
The oil actually flows into the it.
Your electric sender will have to be removed so the oil line can go in its place.
Presently I'm running one from a Morris mini, I just replace the black bezel with the Jags' chrome one.
Fits right in to the dash and looks correct.
My old gauge would stop working all together sometimes.

Great info thank you very much, will follow your lead.