flyboyAP87

Yes, that's correct. But, even though the engine and prop are still turning at the same RPM, with a constant speed prop the change in pitch allows the engine to operate more efficiently for a given RPM. So because of that a variable pitch prop is like a transmission in a car as Tom alluded to. The Continental GTSIO-520 in the Cessna 421 is the most common one I can think of. The prop is geared lower than the engine so the engine can spin faster, which more engine RPM=more horsepower.

In the vast majority of piston propeller aircraft the propeller is bolted directly to the crankshaft. This means that the propeller is always turning the same RPM as the engine. The reason why the RPM is so low compared to something like a car engine is because if you spin a propeller much faster the tips will start to go supersonic which greatly increases the drag on the prop and reduces efficiency. As far as noise goes most aircraft engines have relativity small mufflers or none at all if they're turbocharged. Also, a lot of the noise you hear, especially at high RPM, is propeller noise as the tips get closer to the speed of sound. The thing you have to realize with aircraft piston engines is that they haven't really changed all that much since 50s/60s.

Did you have fuel running out of the bottom of the cowling after you landed? If the float was stuck down and therefore the needle valve was stuck open the fuel bowl in the carb would continue to fill until it was overflowing. I would think with neg Gs though that the float would be forced up and the needle valve closed. If I was to make a guess as to what happend I'd say the fuel in the bowl of the carb was forced from the bowl into the engine and flooded it. If thats the case the fuel would eventually evaporate and/or drain out of the cylinders and the engine would be back to normal.