What I did was to take an old oil return tube and cut about 3” out of it and then splice in some 3/4” ID clear tubing from the hardware store and clamped it with a couple hose clamps. It was cleaner than removing the tube and letting oil run all over my freshly restored engine. I was told by Antique Engine Rebuilding that you should see oil flow in 2 min. Mine was 2+ minutes, so I changed out the rebuilt pump with a new pump from Brattons and I had oil flow in about 25 seconds. Good luck