I had the light stay on for 10-20 seconds at start up too. It was improved greatly by changing the main and rod bearings. I think we've talked about that in another post. The thing is if your oil light is on then you are getting less than 10lbs of pressure to your sender and the rest of the motor including your top end. I'm guessing this means that your having ticking and knocking until that light goes out and probably quieter ticking after. I assume that's what you mean by it sounds like hell. There is no way to prime the motor before you start it, the pump is drove off the crank. When I rebuilt my motor I prefilled all my oil ways by squirting oil into the rocker arm post oil ways before I installed the rocker arm shafts until the oil filled the oil filter and squirted out the other oil way on the other rocker arm. Even this method didn't fill the rocker arm shafts with oil.

In short the only way your going to fix this is by replacing your main and rod bearings. That will buy you time but the top end is probably wore out too and so a complete rebuild will be necessary eventually. After my rebuild the starter cranking the engine shuts off my oil light and I have 28-30psi at warm idle and 40-42 at 2000 rpm. Like any self important bitch you have to decide to love her or replace her, either way no judgment here.

 

wouldn't hurt to check and see if you are losing fuel pressure when it sits for the 2 days, could be a leaking injector... If it is, your oil may be a bit thin from the fuel draining in the oil. try an oil change...