Well, yes, gasoline vapour will settle in the lowest available area, but will remain a vapour. This is common with many "fuel" type vapours and gasses - but, I'm not a physicist. The amount of gasoline vapour which could "pool" or otherwise accumulate in the cylinder, would probably be just right for the intended combustion, when ignited. Now, if it's a radial engine, Hydraulic lock becomes a concern, but that's not quite this topic....