I'm guessing that you did have the valve cover off and front cover when you are they assembled the motor. If they did they might not have put gasket maker like ultra black etc where the seams are. Example the head and block have a seam where you put sealant on four spot before you put on the timing cover. And When you put the valve covers on you have 6 spots you must put sealant on too. Four between timing cover and two on intake cam cover for water pump. Alot people forget to put the sealant on the mated parts. Then If they do they forget to cut the excess off with a razor blade before installing valve cover too. Check to see if it puddling in the center of the motor and dripping down the cover on the belts.
