Jerry -- some of the cowling openings are taped over in winter (usually the hole in front of the oil pan). There's still plenty of air coming in through the main eyeballs on either side of the prop at my insanely high speed flight of 70-80 MPH.
As you probably know, the O-145 is a cool running engine. In temps below 35 it rarely gets the oil warm enough to ensure all moisture is boiled off. (I also have limited baffling (anyone have drawings for the LA-65??))
Prop wash does not cool the engine much -- most of the air is moving outside the circumference of the engine. The Service manual for the O-145 recommends ground ops not exceed 2 minutes in warm temps (!)
Here's an extract from the Lycoming O-145 Operations Manual:
GROUND RUNNING AND WARM-UP-- the LYCOMING 0-145-B2 engine is an air pressure cooled engine that depends on the forward speed of the airplane to maintain proper cooling. Therefore, particular care is necessary when operating this engine on the ground. To prevent overheating, it is recommended that the following precautions be followed:
Head airplane into the wind
Avoid prolonged idling at low RPM as this practice may result in fouled spark plugs
Limit ground running to 4 minutes in cold weather and to 2 minutes at temperatures above 70 F.
Here's some info taken from the Lycoming Flyer:
B. ENGINE GROUND OPERATION
The engine ground operation greatly influences formation of lead salt deposits on spark plugs and exhaust valve stems. Proper operation of the engine on the ground (warm-up, landing, taxi and engine shut-down) can greatly reduce the deposition rate and deposit formation which cause spark plug fouling and exhaust valve sticking.
1. Proper adjustment of the idle speed (600 to 650 RPM) fuel mixture, and maintenance of the induction air system will ensure smooth engine operation and eliminate excessively rich fuel/air mixtures at idle speeds. This will minimize the separation of the nonvolatile components of the high-leaded aviation fuels greatly retarding the deposition rate.
2. The engine should be operated at engine speeds between 1000 and 1200 RPM after starting and during the initial warm-up period. Avoid prolonged closed-throttle idle engine speed operation (when possible). At engine speeds from 1000 to 1200 RPM, the spark plug core temperatures are hot enough to activate the lead scavenging agents contained in the fuel which retards the formation of the lead salt deposits on the spark plugs and exhaust valve stems. Avoid rapid engine speed changes after start-up, and use only the power settings required to taxi.
3. Rapid engine cooldown from low-power altitude changes, low-power landing approach and/or engine shut-down too soon after landing or ground runs should be avoided.
4. Prior to the engine shut-down, the engine speed should be maintained between 1000 and 1200 RPM until the operating temperatures have stabilized. At this time, the engine speed should be increased to approximately 1800 RPM for 15 to 20 seconds, then reduced to 1000 to 1200 RPM and shut down immediately using the mixture control.
Also:
Extended ground operation can cause excessive cylinder and oil temperatures.
More:
Preventing a buildup of contaminants is just as important as eliminating those that do form. Avoiding long periods of ground operation is a vital step since moisture can enter the breather, but will not vaporize when the oil is not heated to normal operating temperatures. Ground running also involves a slightly rich mixture which contributes to the formation of lead sludge in the oil. During flight, the deposit of lead sludge in the oil can be minimized by proper leaning.