Sorry I dont have alot of info as the car isnt here and I am only relaying what I was told. It a 302 in a 80 Bird abd after about an hour of driving, which it runs fine, the oil pressure drops and of course the rattling begins. Any thoughts?
main bearing?
mine drops from 50 lbs to about 0 in 40 min.
then the clunking starts
Main bearings would be my guess as well - they're so sloppy the oil pump can't keep up with the oil being thrown off the crank when it's hot (and thin). Try an oil change with a heavier oil (20W50 or so). It won't repair the problem but it might buy some time...
it could be the pick up tube screen is clogging up. if the plastic cam gear goes south all that plastic goes into the pan. the reason i say this is if it were bearings it would start to rattle as soon as it is warmed up. where if it is the tube plugging up it happens after a while of driving. sorry but my guess is that the oil pan needs to be pulled and cleaned out. and also you might as well put a pump and tube in while you're there.
Which is one helluva job with these cars.