the spring reduces the flow of oil to be recirculated in the pump. The AMC V8 oil pump recirculates this oil when the pressure in the return from the oil filter becomes to great for the spring and the plunger moves back. Stock springs allow a higher percentage of oil to be recirculated in the pump and in extreme cases the oil pumps do not put out much volume. We have found that the stock spring weakens over time nad especially when the engine is overheated! In turn causes no#1 Cam bearing degridation, lifter diameter change due to friction and eventually a spun main or Thrust bearing wear causing rod knock. Stock springs are rated for 250 degree's and loose their ability to spring back after they have been repeatidly overheated. Here are examples of where the oil flows when the plunger is pushed back.