Daimler V8 250 saloon oil pressure relief valve

[djpeters23140]

Hi all. I have decided to try and improve my hot low idle oil pressure which is about 10-15 psi at 600 RPM. I have changed the big end bearings and I am replacing the oil pump relief valve. I was surprised to find the existing valve has a small hole through the centre which would allow oil to pass through even when closed under spring pressure. The new David Manners one does not have such hole. Has anyone found the same or has a theory. Dave