Ford: oil pressure, shaft bearings, ford f100

Question
i have an 87 ford f100 with a 3.8 v6 when the truck would warm up the oil light would come on when not going highway speeds, or when ildleing, and i could hear some chattering from the engine, possibly lifters or valve chatter. i thought it was the oil pump so i put in a new oil pump.what fun! i got it all together,but it still does the same thing. help. what else could cause this?

Answer
Either you have a lose lifter, bad push rods, or cam shaft bearings are worn out. If the vehicle doesnt have alot of high miles then you should have it repaired. If the vehicle does have high miles, you can try some engine flush add to the crankcase, run for 5 minutes, then change the oil. Ty