RE: Kangke Waco Biplane
Good idea getting the Bennett gear braces right away. I would definately recommend them to save your props.
You can't go wrong with the ZDZ40. Excellent power, easy to run, and lightweight. That is what I have in mine. The Waco instruction manual shows this motor installed on Kangke's test plane. The only "hacking" of the cowl was on the bottom for the cylinder head and is pretty minimal. You cannot see this at all from the side of the plane. It does not detract whatsoever from the looks. Vertical is unlimited.
I considered putting a saito 300 in mine when I was building it but that would have required alot more finesse as far as fitting the heads inside the cowl. The other reason I stuck with gas is that a smaller fuel tank can be used. If you go nitro, you will have to put a rather large tank in there.
Other good options for gas would be the RCS180 on the small end of the range or the DA50 on the larger end of the range. The DA50 is an awesome engine- very lightweight, very powerful, and looks incredible, but,,,,, its expensive. The brisson 2.4 would work too and you may be able to get a nice combo deal from your local dealer by buying these together since Kangke distributes them. The Brisson definately won't have as much power as the DA or ZDZ though.