Here's a possible.  You could have iced over the crankcase breather exit and
pressurized the case.  It happened to a friend under very similar
conditions.

The fix is a aft facing hole about 1 or 2 inches from the end of the
breather pipe or routing the vent within 1/4 inch of the top of an exhaust
pipe just below the firewall (this also helps vaporize the oil/water vented
for a cleaner belly).

While I am talking about crankcase vents, I should mention "Air/Oil
Separators".  I have one of the Aircraft Spruce variety on my O-360 in a
RV6.  Instead of returning the aprox. 80% oil, 20% water to my crankcase, I
have a 12oz catch can with a screw on lid to hold the blowby liquid.  Three
reasons, one is to minimize the belly stains.  Two is to monitor the volume
and mix accumulated between 25 hour oil changes.  Three is to keep this
oil/moisture/acid from returning to the crankcase.

Steve Colwell   Legacy 2K  Placerville,CA   (530) 621-3408

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