When you pull off the oil filler plug with the engine warmed up and running, is it normal to see a small amount of oil fume? That's what I see, maybe its a symptom of the blown head gasket I mentioned in another thread. Don't know, what do you see with a rebuilt astron II motor, that you know is not burning any oil?

tatally normal to see a little bit of smoke like that on older engine (even if they are rebuilt)

to improve

clean out PCV valve at the end of the rocker cover

some owners
buy cheap inline fuel filtes as an extra filter for the vapors

later replace the valve stem seals