Wierd oil pressure readings

[lvrpool32]

Ok so had my car at the track in October, ran great, oil pressure was a little lower as i put it back in the trailer (normally cold its45psi..upto 65’ish when revved, it was down to 25 - 30 idling at the end ofday, I’m using 20w-50W race oil with no cooler (yet)),I put the lower pressure down to being driven hard for the first time.
Anyway come to move it today and the oil pressure gauge takes a while to move..but it starts to move and slowlllllllllllllllllllllllllllllllllllllllllyyyyy yyyyyyyyyyyyyy gets to 20....when I rev it, it goes down! Now I have an oil pressure safety switch on the fuel pump but that worked fine, right away as the motor cranked, so I effectively have one safety system contradicting another.
I changed the oil to a 10w – 30, and the gauge went a little higher, but still went down when revved (have to say the engine is running great,no funny noises and when I say revved I’m talking 1,500 rpm over idle)
So my question is, has anyone seen mechanical (autometer)gauges go bad? (it’s a 4an line from the fitting by the distributor, small blockChevy) (I have a VDO gauge I am going to rig up and try this week)
My other theory is that maybe the pick-up in the oil pan has moved/fallen off/clogged. I am not using a high volume pump.
any other ideas?
Cheers
Nick

[exwestracer]

Longshot, but it's possible the pickup fell off the pump. As you rev the engine, more oil gets thrown up inside, so the pan level is lower and the pump has a harder time getting oil (lower pressure reading).

I've seen it happen just like that once.

[Thephranc]

I just had my oil pump pick up tube fall out. It was catastrophic. I was getting odd pressure readings too.

[lvrpool32]

well I was planning on pulling the motor and trans anyway to swap to a SFI bellhousing and an upgraded clutch so I will see what I find.

[Steve Chryssos]

You might very well find that all is well but the pickup is full of trash like gasket material or silicone. Good luck.