GMC Jimmy Oil Low Pressure

I Have A 1997 Jimmy When I Start It The Oil Pressure Is Around 40-45 And Drops To 30 Or 35 When Is Warm, And Goes Back To 40 Or Just Above...

I Just Rebuilt My Jimmy (4.3l) Vortec. I Put In A New Oil Pump,crank,mains,rods,rings,no Cam Bearings,or Cam.why Won't My Oil Pressure Get...

Truck Has Excessive Mileage And Internal Engine Wear Is Starting To Show Thru Oil In Exhaust, Crank Bearing Rattle, Low Oil Pressure At Idle...