Oil Pressure ?

[shaunstaples]

It all started when I bought an oil pressure gauge....

Its always been high hitting the relief pressure (about 120psi) when cold as the revs increase. (I intend to lower this later on, with a lighter spring).
When the oil was warm, not hot, the pressure was dropping to nothing on tick over and barely 5 psi, when revving on my initial SAE40, only just better on SAE50.
The next improvement was fitting a filter on the return and changing to 20/50 where I was flickering on tick over and barely 10psi with a good rev.
Still not happy, I tried some 10/60 which increased slightly again, but still unable to reach 30psi when revved and hot.
Next I got spare oil pumps from Newark jumble and the feed pump gears are about 0.0025" thinner than the centre plate (same as my original feed pump) and the end plate is also worn, so I've faced the end plates and reduced the centre plate taking out the side clearance, the pressure is now 5psi on tick over and over 40psi when revving after a run to warm up.

I've read somewhere 30psi when warm, will that be when revving or on tick over and I've got some way to go yet ?
Also are lighter relief valve springs available or is it keep trying lighter ones until cold relief pressure comes down? 75 psi ?

Any help appreciated, thanks Shaun