Aircraft engines are set to run with a perfect fuel/air mixture at sea level
They are not set to run rich on the ground. Running rich will cut
down on the power available, which is full power. As the aircraft
climbs the mixture become richer than at sea level, the same as your
car does....losing power at high altitude.
That's right and why the carbs are set richer. Full power is a richer than economy, and especially the "save the earth" lean that automobiles run at.
Aircraft engines do not have looser clearances on the ground than
they do in there air. This is about as foolish a notion as I have ever heard.
I didn't say they did. I said they have looser clearances. I should have said they have looser clearances than automobiles, at least as far as the piston, rings, and cylinders.
There better not be any blow-by in the aircraft engine at any time.
Most aircraft engines use an extra set of rings to insure that ring seal and
compression are kept as perfect as humanly possible, and that blow-by
is eliminated at all times.
If that were true I would have been replacing cylinders every time I started the engine up, instead of every few annuals. Funny but for each cylinder I had to replace I recall replacing two compression rings and an oil ring. Granted some have an extra oil ring and many have the oil ring located at the bottom of the skirt. I suppose they put the crankcase vent on just for the heck of it. And I guess that air that leaked on the compression test wasn't blow by. I don't know how they seal the rings so well, I mean they have gaps in the rings just like automobiles and trucks, they have looser clearance because of the higher expansion and contraction of the cylinders. They also have high lead fuel, valves that tend to stick every few hundred hours, magnetoes that still use points, and a hundred other thing much inferior to a standard automobile engine.