68 Z/28 Engine Smoking - Any Ideas?

[GreenLS6]

I'd do a compression test first-check balance between cylinders.Look for something obvious. Then a leakdown.
O-ring seals SUCK. Machine for teflon seals or at least get the good rubber sleeve seals(they stay put and last longer) Depends on the valve springs you have though(Internal diameter) If it's only smoking when you stop then check the needle and seat or spray carb cleaner around the intake gaskets. You have higher vacuum at idle a may suck oil from a warped intake . Although a MO doesn't have much vacuum anyways. But it sounds good doin it!!
Good luck

[njsteve]

On the warped intake idea, you can also have a leak on the underside of the intake that sucks oil from the lifter valley into the intake runners without ever giving any indication of a vacuum leak on the outside of the intake.

My vote is for the dried out rubber o-ring valve seals. After sitting a long time, those things can just fall apart on their own. They would also give an inconsistant oil down that would occur randomly and not all the time, depending on oil flow/engine rpm.