Actually the engine has several parts (well lots actually) ranging usually from very warm to extremely hot. The warm areas are usually around the air intake areas and the hottest parts are usually where the exhausts leave the engine block. It depends on what fluid and how combustible it is as to the events that unfold and at what rate. Coolant for example will generally just run out unless splashing onto something like the exhaust manifolds and then it will steam. Oil will generally smoke a hell of alot on the hotter parts of the engine and sometimes even when on the exhaust manifold. But once oil gets on a manifold of an engine that has just been screaming its guts out, then there is a very high chance of fire. Then it also depends on air (oxygen) quantity. Too much or too little and no fire. That is one of the reasons why going into a dive will assist in sometimes putting out a fire. That and the fact that it is blowing the flame out. Actually blowing the flame out is the result of supplying too much air for the fuel in a matter of speaking. Alot of aircraft would get a hit in the block and oil would splash about everywhere and depending where the hole is and how big as to how hot of a surface the oil landed on and the resultant smoke or fire. Now fuel is a different kettle of fish as it has a lower flash point and if a fuel line is hit, the chances of fire are alot greater from hot surfaces as well as the fact that it takes a heck of alot more air velocity in a dive to put the fire out if at all. Sometimes it will just help the fire get worse. fuel is pumped into the carburetter at a reasonable pressure, so a leak is likely to spray all over the place.
Now the next time you get coocked in your cockpit, you may have some idea as to the contributing factors.
Happy flying.
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