04-02-2018, 12:01 AM
As discussed on the old forum, when I complained about my Chummy oil pressure coming back onto the gauge from cold quicker than I expected, Ruairidh suggested it might be the result of having the pump vanes fitted the wrong way up. This proved to be the case. It wasn't clear how long they had been wrong - the car had been in the USA for fifty years carrying out very light duties, so it could have been a while. However, this showed that the pump performance was significantly affected. Although the chamfer is small, the vanes must rely on the square bottom edge of the vane pressing on the pump base plate to form a good seal. When incorrectly fitted, the presence of the chamfer must allow some oil to squeeze under the vanes and so reduce the efficiency?
Colin
Colin