O.K. I'm working on designing a simple twin boom semi aerobatic twin. I need some suggestion for make and model of engines for this project. My primary concern is engine reliability. I am trying to keep my cost low--high performance is not what I am looking for. I will be staying in the .40-.46 range for this project....

right now nobody builds a bad 40/46 because they can't afford to so take your pic even the very cheap Ching engines are getting better and better. fuel , tuning, and break in is far more important than the brand.

In my opinion, it's no contest......the O.S. .46

It's powerful for its class..only runs a few hundred RPM under the expensive, poor idling "racers," and, more importantly for twins:

It's very reliable. I've run several of them, including a reverse rotation version for a Duellist, and I can't remember having one quit on me unless I did something stupid like run outta fuel or forget to change the glowplug once a year.

mt

I have found the FP series O.S. engines to be very reliable, fuel efficient also. But if you have the $$$, I would go with the higher end O.S. .46 as kram has suggested.

While I fly a lot of non-OS brands (MDS, Magnum, ASP, GMS), I prefer OS engines for twin use. My reasons for this is that the consistency in quality and workmanship for OS engines is much higher than other brands. Having a matched pair of engine is desireable for a twin application. Both my OS .40 FXs on my twin spin the same rpm at same throttle setting and are easy to match.