OK, I didn’t get the ‘project’ bit from your earlier posts, more a what’s the minimum to swap engines to keep the P38 running for some more years.
Yeah, that's my fault. I didn't indicate at all that that's what I was doing. I might even have decided on the current plan after I made this post lol.
However, what is the evidence that the original engine has low oil pressure and if confirmed and not the oil pump then what else can it be? For really low oil pressure there must be a hell of a leak somewhere (internal or external) or the bottom end must be rattling like a good ‘un. Either way, the original engine must be a bit of a risk to refurbish if the cause isn’t known.
The oil pressure light started flickering on and off at idle. It would go away with revving the engine. Over a period of a few weeks the light came on steadily and stopped flickering. The amount revs needed to make it go off increased too.
I took it to a garage and had them test the pressure with a gauge. They confirmed it was low. I don't remember the exact figure but I think it was near 0 at idle and barely made double digits when revved. Just enough to put the light out. I had a new oil pressure sensor anyway so I had them put it in just in case. The light stayed on.
I parked the car up for a while and when I was furloughed at the beginning of COVID I bought my own oil pressure gauge and I changed the oil pump. The light stayed on and the guage read almost nothing. Then I left the car alone until now.
There's no oil leaks and there's not any serious knocking. There's a slight rattle that I thought was more cat/exhaust as pushing on the exhaust changed it. A few thousand miles before the pressure dropped I did the head gaskets. I guess it's possible I screwed something up or loosened some crud that has floated around the system and eventually blocked something. The oil pick up in the sump is clear though.