took the oil pump out of my 302,put it in the solvent tank for a good cleaning. it was not that dirty inside. it looked pretty good. i few days ago my lifters started to rattle and my oil pressure went way down. how would i tell if the pump is bad? the drive rod is fine.could a piece of something got hung up in the pump???? i changed the oil and filter and have all the pressure i want now. i don't trust it, so i pulled it a part to clean and look at it. what do i look for ?? thanks.