I understand the pump is not a pressure pump but a sump scavenger, but I'm not sure how much flow I should be seeing. Its returning oil to the tank ok and plenty is getting to the rockers, but when I look in the tank there is just a constant dribble from the vertical return pipe. I've taken the pump apart and it looks to show no signs of abnormal wear. I'm spending a lot of money on new big and small ends, so I need to be sure they are going to receive sufficient oil flow. anyone any ideas on how to check and test oil pumps?
Once the scavenge side has emptied the oil in the sump, it will constantly pick up a mixture of oil and air , hence the intermittent flow when you look in the tank.
There will be a solid flow from cold as it empties the oil that has dribbled down overnight , but once that is back in the tank , you will get intermittent again.
You're getting a good flow to the rocker banjo feeds , so must be plenty returning.