Replaced oil pump, still having problems
 

The other day I was driving and my oil pressure dropped suddenly. It continued to drop sooner and sooner after being started until eventually it started knockin so I turned it off. I assumed it was the oil pump so I went ahead and changed it and the screen. I started it after I was FINALLY done and it ran for about 5 minutes and then the pressure dropped again. Anyone have any idea of what I may have done wrong or need to do still??

Its a 87 with a 351. Title says 41k original miles but Im not sure if I believe it.

Ive replaced the starter, batter, plugs and wires, air cleaner, and now the oil filter since I got it about a month and a half ago.

I have seen the oil galley's in the blocked clogged. If this is so the pump could be pumping oil up and it is not making it back down to the pan fast enough and the pump is running dry. That may be why it will show pressure when you first crank it and then it drops of.

Could be caused be excessive bearing clearance.

-Jon

how could I find out whether the block was clogged or not and fix it? I will check that and the bearings, anyone else have any ideas???

Essentially the only things that can cause low oil pressure are:

-Bad pump/clogged pickup
-low oil level
-severely diluted oil
-bearing clearance

-Jon

That has my vote.

okay....i have some basic automotive skills and access to help so what exactly am I going to need to take care of this project?? Just the main bearings and spacers?? Can anyone give me a quick overview of exactly what I need to do?? So far Ive done all the work myself and taking it to a shop is far out of my budget. Thanks for your help!

You could do the main bearings and rod bearings. Really the engine is probably due for a complete overhaul, but if thats not doable right now the bearings will get you by. I've never done a set of bearings with the engine in the truck on an f-150 before but if you get a set of bearing roll out pins you should be able to do it all in the truck. I've done it on VW engines that have a lot less room! Make sure to plastigage everything when you put it back together.

-Jon