Odd oil pressure readings

[tr5sean406]

Hi guys a newbie to this forum. I have a 1967 series 1 4.2 2+2 that i am very happy with (except for an annoying bit of of what I'm told is piston slap!) However last year I started getting really odd oil pressure readings, When staring the car the needle would go all the way way to the right and dis appear off the scale then stay like that for a while (minutes) then the needle would go all the way to the left and show 0!!
Then it would go up and down randomly and finally finish about where I would expect normally but may wander off again!! I had the dial out and sent it so Speedograph Richfield who overhauled it for me and on refitting I still have the same problem!! Any ideas??? The car runs fine otherwise!!! Sean

[JimboV8]

Have you checked the oil pipe is not partially blocked?
Is the oil level correct?
How about the oil pickup in the sump?

[3.8etypephil]

Almost certainly the large sender unit adjacentt to the oil filter is faulty.

[piman]

Hello Sean,

another possible contendor is the oil pressure relief valve sticking, particularly until the engine warms up? Temporary substitution of the pressure gauge with a mechanical one would be worthwhile.

Alec