Last time I had a oil pan off a small block to replace the timing chain and gears and gaskets before installing the engine,I saw many of the nylon teeth off the cam gear were lodged in the oil pump screen,and a few made it into the pump--the screen can and does get sucked away from its holder and will let trash get sucked into the pump during a cold start,they figured getting dirty oil was better than starving the bearings completely...........................................................................................Many times that screen is completely covered with carbon or sludge,and is difficult to clean--for 12.99 I bought a new stock melling oil pump from Autozone,and they also had a steel sleeve for the drive collar for another 5 bucks or so,and a new screen wasn't more than 10 bucks so I replaced all 3 of them,rather than risk using the original pump............................................................................................................the worst part of changing the pump is installing the screen to it,its tricky and I never liked the way they rely on just a press fit to secure it--nor do I like the thoughts of welding or brazing it to the pump,a precision made unit that likely wont tae kindly to that much heat...so far I haven't had one come off,maybe I am lucky,some other guys I know had them come off and end up in the sump,and their engines scored the bearings..
I'd rather know its good
