Almost any gasoline engine will be MUCH too large for the Top Flite Cessna 182 kit. The airplane flies very nicely on a .61-.75 size two-stroke engine, and maybe a .90-size would be OK for those at higher altitudes or if they built the airplane to be too heavy. A 1.20-size four-stroke engine is just under 2 pounds of weight. A gasser of similar size could be a pound or more heavier, which means more weight added to the tail to balance it.

The airplane is intended to have a completed, ready-to-fly weight (less fuel) of 10-12 pounds. Make it heavier, and the flying characteristics will suffer.

We really can't recommend going to a gasoline engine, you'll have weight problems as well as difficulty fitting it into the cowl.