 Figure 1: 8mm USA Marking on Oil Pump  Figure 2: Tab on HD Oil Pump |
Question: How can I tell the difference
between the regular and HD (heavy duty) oil pumps? Answer: The standard oil pumps that came with the 914 motors had VW part numbers on the back side of the pump (visible from the outside of the motor). The HD pumps made by Melling have the markings 8mm and USA on the back face of the pump. This is shown in Figure 1. It is important to note that the Melling pump has a small defect / design error built in to the pump. The small tab that powers the pump, shown in Figure 2, is too long. When tightening the the bolts that hold the pump to the engine, this tab will press against the camshaft and apply a preload to the bearings. This loading condition will cause premature failure of the bearings when the engine is run. The fix for this is to grind about 1mm off of the tab (indicated by arrow in Figure 2) so that it will have enough clearance to fit into the cam-shaft. |
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