Is there any advantage of using a HELI engine for a plane?
If a .90 size engine is mounted in a biplane for example, would it have better performance than the standard plane? If YES, is the price difference worth it?

Any one who has done it, please share your knowledge
THNX 4 helping

We use Irvine 36 heli engines in some planes just because the give that little extra go, they are designed for full throttle piped flight and so are great for this, not sure how well they would act when left with a standard muff and setup. im sure it would be fine, but probably not worth the extra cost. the large head for cooling is a bonus tho

I had a 61 os surpass and put a o.s 32 heli carb on it and the difference was incredible in all areas. the heli engines have superior {o.s} carbs and can work on several types of engines if adapted to fit properly.

Well - one of the fellows here has an old OS .32SX heli engine in a .25-sized pattern plane (can't remember the name of the kit offhand). He'd retired the engine from heli use - many many flights in a Concept 30.
Performance is sparkling - it's really too much power for such a small airframe, as sudden applications of power will torque it HARD.