smoke from engine

lescure wrote:
Hello all,

This afternoon I made a flight with my Safari 30 minutes and after
refuelling I started again the engine and there was a lot of smoke coming
from the exaust. very impressif. A guy from the local air club told me this
could come from one valve not correctly positionned whenn the engine was
stopped.We discover later that there was plenty of oil in the exaust svifel
. Some oil was even leaking on the heating duct. Finaly the smoke disapear
after 2 or 3 minutes running.
Any body has an idea of what exactly happened? The engine is from a crashed
r22 and has 700 hours since new. All gages oil pressure temperature cilender
head are ok .All comments welcome

I don't have any experience in aircraft piston engines, but I've seen
car piston engines do this when the valve seals get old. A little
bit of oil leaks past them and is quickly burned off as soon as the
hot engine is restarted.

Ideally it should not do it at all, and it will get worse, not better
if you have no work done to correct it.

The quantity of oil you describe is surprising, but maybe that has to
do with the position the engine came to rest on shutdown. Have you
checked for that on subsequent shutdowns and hot restarts? Also,
what is the engine's recent oil consumption?

You can take a little comfort in that only a few drops of oil can
make impressive size puffs of smoke.

Thank you all
Stuart Fields a very experienced Safari builder and owner found the
solution:

Oil smoke. I found a depression in the crankcase below the cylinder(I think
it was #4) that held a couple of tablespoons of oil. It can bleed down into
the cylinder. I drilled a 1/4" hole in the bottom of the depression to
drain this oil down into the crankcase. This oil does not collect in a
horizontal mounted engine. This mod stopped my engine from doing the smoky
start like the one being described here. The only way I found the
depression was searching for the problem, I pulled the cylinder suspecting
valve troubles. When I found no valve problem, I continued looking until I
found the puddle of oil setting there. Apparently it is the only spot in
the crankcase to collect the oil in such a manner as to make it avalible to
get down into the cylinder and out thru the exhaust.
Stu