The "radiator outlet pipe" or "water outlet elbow" appears to be a 90 degree angle. Dimension is 1 1/4" OD. Available at Filling Station or Billy Possum. I used the elbow listed for the 1929-34 and it was an exact match replacement for my 1928, including the ones on a couple spare engines, all of which were very deteriorated. Both the above vendors recently listed the elbow for the '28 as a separate part, same price. In the photos at Billy Possum the '28 appears to have a slightly longer end on one side of the curve. That can be made up by cutting the hose a bit longer, if necessary.