<VV> Turbo oil smoke

[Jim Simpson]

My '66 Corsa turbo has developed a bad habit lately of blowing oil smoke
while at idle.  (It's definitely exhaust smoke, not a leak.)  Sometimes
it's enough to take care of the local mosquito population.  It is a bit
erratic though.  It seems to be worse when the engine is hot idling in
traffic, but then after a highway drive it can idle in the driveway with no
visible smoke.  Fellow Corvair owners who have driven behind me haven't
noticed any significant smoke while cruising.  The overall oil consumption
doesn't seem to have changed very much, but the smoke is a bit
embarrassing.

Any suggestions as to cause?  My preliminary guesses are the oil seal on
the compressor side of the turbo, a bad intake valve stem seal or worn
valve guide(s).  I haven't run a compression check, but the engine was
built about 15k miles ago with TRW forged pistons and Total Seal rings and
hasn't been driven hard.

Does anyone have a good suggestion as to how I could isolate the problem?
I have a spare turbo with what "should" be a good oil seal.  I may swap to
find out if that's the problem.  But is there any simple way to check valve
stem seals without pulling the heads?

Jim Simpson
'66 Corsa
Group Corvair