Inliners International Forums General Discussion Engines gray smoke, 292

My rig ('68 C10 w/292) is putting out a puff of greyish smoke at startup after sitting for a while. I'm thinking oil is leaking down past the valves while sitting. Would this be valve stem oil seals?

Sorry for my ignorance, but how can I tell if my rig has hydraulic lifters or mechanical?

thx, eric