[Barlea]

These are not barbed fittings, they are for hard lines and the later ones fit up to manufactured flex lines, the ID is 3/8" or very nearly so, when the bottom of the brass fitting is drilled with a 3/8" bit it only takes a very slight amount to allow the 3/8" thinwall tube to slip in. The tube fits into the oil port the same as the factory fitting to block the horizontal passage except the factory fitting was machined in one piece with the same dimensions. Bear in mind the factory designed the oil passages with ample size for the flow that the pump would produce and a slight restriction would not cause any constipation to worry about. ..B.