Micah Froese writes:
> I am getting oil on the belly of my Continental IO-500 powered
> Legacy. When I shut down after a flight, the breather tube makes
> a mess on the ground.

I had this problem for a short time with my O-320.
The problem was a stuck compression ring caused by
carbon accumulation. The stuck ring caused excessive
blowby, which in turn pressurized the crankcase, blowing
oil mist out through the breather. Another side effect was
foul-smelling, black oil. Oil temp on the high side also.

A complete engine rebuild solved the problem, but just
cleaning the piston ring grooves would have sufficed.

Did your oily belly start recently?
Or has it always been a problem?

How's the compression? Got a low cylinder?
Does the oil smell bad or darken quickly after an oil change?

Crankcase pressurization can be checked by fitting a pressure
gauge (airspeed indicator) to the oil filler tube. According to
the Sky Ranch Engineering Manual, a Continental IO-500 (or 550?)
should show no more that 95 mph during a ground run.

Other possible causes (again from SREM pages 346-347):
2. loose seal on oil filler
3. engine breather exposed to low pressure
4. nose seal loose
5. (applies only to IO-360)
6. Defective wet vacuum pump (Garwin or Pesco)
7. Poor engineering at the factory. Call service department.
   (yes, it really says that)