I pulled the valve cover and there was oil on the passanger side and no oil on the driver side. why? oil pump? please help hence thats were the knocking is coming from

 

When the main and rod bearings are shot (knocking from the bottom of the engine), there will be very little oil pressure to get oil up to the head. What is the history of this problem? Did you run out of oil? Oil light coming on?

Or the oil passages could be clogged with sludge. Is there sludge on the rockers, etc?

 

no sludge on the rockers. just bought the car back from a friend said he was driving down the road and heard a little knocking then it went away two days later he was passing a semi and said it went POP loud and smoke everywere. now its really loud. no oil light on dont think they ran it ous of oil at all.
so what do you think the knocking is from???
thankyou and oil light comes on befor you start it like all lights do then off when its running