Have a 1466 IH that is slow to get oil pressure on the gauge. Tractor has been overhauled about 700 hours ago by an IH mechanic before I bought it. Guy that owned it said it was always slow to get oil pressure. If it sits for a couple of weeks it will take 30 to 40 seconds before oil pressure comes up on the gauge,and top end of the engine will rattle for a moment, when it is getting used every day it still takes 20 seconds but no noise. Has good oil pressure after it starts, about 60 pounds, and hot engine at an idle will be 30 pounds. Seems like all the oil drains out of the filters when it sits very long. The oil filter housing has a nut on the right hand side of it, that I took off and all that is in there is a spring about two inches long. Is there suppose to be a valve of some sort in there? Any ideas whats wrong? Thanks.