this is a long time ago, but i just ran into this and it sounds similar, so maybe it'll help someone. rebuilt one of these motors out of a 95 topkick. the distributor was bad, so I bought napa direct replacement PN# NNDST1830. no knowing, it cut off oil
flow in the main galley, but shows oil pressure. after rebuilding the motor again, i machined the new dist. to stop the oil passage blockage.

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