I am just fishing for some information.
My buddy and i are rebuilding a b18c1 and a b1881. On the block on the back(towards the engine bay) there is a black box that I believe is labeled the oil breather. What is the function of this black box? Do they go bad, need to be replaced, cleaned? My engine is at the machine shop and hopefully they will take care of it, his on the other hand is not.
Anyone?

 

that's an oem catch can, it cant go bad, you could change the o-ring though