I swapped a B18C1 into my Civic a few days ago. So right now I don't have a cat hooked up. It'll be in later on this week. When I bought the swap 2 months ago I put a tablespoon of oil into each cylinder, to prevent surface rust from settling in. So I expected it to smoke when I first started it. It did, but whatever....I knew why. I ran it for maybe 10-15 minutes tops. I started it up again tonight and it still smoked again. Not as much as last time but it did nonetheless. It only did it at startup but not after.

Could this be residue from the oil I put into the cylinders or might my valve seals be worn a bit?

 

It's definitely oil burning, the source could be from blowby, or valve stem seals, and less likely a head gasket leaking..

 

as sensei said its oil...as where...not sure where to start but sensei has got u goin the right track