Hi Nobby,
I made some tiny ones for the headstock of a Perris (now evolved into the Cowells) baby lathe, as shown on the bottom third of this page. They work surprisingly well. The central tubes simply drop down the original oil holes but for a non-static application like the big end of an engine, screw-in fittngs would be better.
You can test the siphoning effect with a bit of wool,a small container (such as a bottle top) and a saucer. Half fill the bottle top with oil, stand it on the saucer, submerge one end of the wool in the oil and let the other end rest on the saucer. After a while, you will have an empty container and a puddle of oil in the saucer.
Andy