That is the way that you can tell that you still have oil in the crankcase. Show me a stovebolt that doesn't leak some oil and I'll bet the oil pump pickup is high and dry. The breather pipe is there to suck fumes out of the crankcase as the truck is going down the road. With the fumes, some oil droplets are drawn out as well. Unless you have a puddle of oil, you need not worry. There is a plate inside the crankcase behind the hole where the pipe enters the block that is there to reduce oil from entering the pipe. It is held on by a slot head screw from the outside. If you can see the screw, then it is likely that the plate is there since that screw threads into the plate. If the plate was not replaced during rebuild I believe that you would have a significant leak.
