I think to swing a 4-blade prop with scale diameter (20" diameter prop on a 66" span plane), it is more efficient to use a gear-reduced engine such as RCV, or electric motor. I don't see too many RCV engines around, maybe they never catch on? However, electric is coming like a storm and we're just seeing the tip of the iceburg.

Now some people have come out with "warbird sound speakers" to install to your planes to make electric motors sound like WWII engines. I am not sure how well that would work out logistically, or how much more battery power is required to make impactful sounds. But I will tell you one thing: no glow or gas RC motor sounds like a Merlin quite yet.