I have already tried thread tape. I am going to pull the front end of the engine back off to check the lower cover. Like some other fools on this site I got this truck in "project" status. It had a cracked head along with some other issues. I replaced the head with a 4d56 head off of ebay. Had the injection pump rebuilt and installed new injectors. When I started it the oil pressure pinned at 100#. I have seen this before on other engines and felt it was the pressure valve in the oil pump. I went looking for parts and the only oil pump part seems to be a 'repair sleeve". I am not certain what the repair sleeve even does. My magic googling came up with this pump assembly from Amazon. I guess all I can do at this point is transfer the parts from the Amazon pump to the original housing. I have ordered a new lower gasket set which should be here Friday. That will teach me to get one of these new trucks. My 1973 Datsun 620 just keeps running