Seems as no oil is getting to the top of engine

Your oil pump is going out, Their is a little screen on the pump that can be blocked from gunk, Also the oil chanels fron the pump to the top of the block are blocked up. If so you can try a old trick of a gallon of Deasel fuel to a full tank of gas and run that into the system this will help out and their is also a additive you can buy and this helps out. But its not a quick fix. Untill this is fixed were you are getting more oil to the top of the lifters dont hot rod the motor because it will LOCK UP... If you are looking for a quick fix take the car to the shop and have them rebuild the block. But you need to change the oil on a reg. bases. So start small and change the oil and filter check the oil pump and screen. And then add some oil cleaner from a parts store.

Remove the valve cover, start the engine and find out. If this is the case and the top of the head is not all gummed up with sludge replace the oil pump. It the top of the head is gummed up the inside of the engine must be desludged before you install the new oil pump.