Some oil pump ramblings...........
Correct, no gasket. Also yes, the pick-up housing has a thin paper gasket where it attaches to the pump housing. Packing the pump gears with vasoline will help prime the pump during first start. Over torquing the pump bolts will cause a bit of binding, but will run in and free up if not too bad. Scores and scratches in the top housing can be smoothed out by removing the long gear and "lapping" the housing on a glass plate with a bit of 600 wet dry sandpaper and water. I always install a new oil pump on a total rebuild. It is the "heart" of your new engine. Unfortunately quite pricey! But so is a new engine!
The combination of scratches and scores in the gear box walls, and the upper housing, along with wear on the gear shafts and the gear shaft bronze bushings, will reduce oil pressure. Complete oil pump failure on a used unit is not likely, however the built in oil relieve valve (later versions) on rare occassions fail.
During catastrophic engine failure, a lot of metal particals are circulated through the oil pump. In these cases it must be replaced.
Latest versiion M130 engines use an increase capacity steel oil sub-pan. These oil pans can be identified by the ribs in the steel bottom of the pan. In this case a rubber extension is used on the oil pump pick-up. If you are not using the ribbed pan, do not use the rubber extension.
