I just got this motor installed about a month and a half ago, and noticed it has a bottom-end knock at startup. I'm wanting to know how typical this is and if anyone has had serious problems evolve because of this. The motor is now an 01 318 and had around 79000 miles on it when I installed it. I know of alot of motors that have a knock at startup and don't have any other problems. I just hate hearing that noise. It only does it when it sits for awhile, and only knocks about 4 or 5 times and then the oil gets to it and is fine. I'm trying to figure out if I need to try and exchange it for another motor. I have about 2 months left on the warranty.

 

I had this happen to me with a small block chevy because I forgot to tighten a rod cap all the way. To me, any knocking going on in the bottom end of an engine is never good. Pull the pan and check it out. May be something simple. Did you re-torque the mains and rods when you installed the engine? You may want to go back and check clearances while you're in there.