A .46 FX or AX would be plenty of power for the Alpha .60 trainer. A plain bearing .46 like the .46 LA probably wouldn't be enough power. Which model do you have? Also, I'm describing "plenty of power" as smooth easy take-offs, basic loop and roll aerobatics, and flying on the wing.

Also, engines with tuned pipes tend to be an all-or-nothing kind of power source. By definition, tuned pipes are tuned to provide improved performance at wide-open throttle (WOT). If you're not flying at WOT, then an engine with a tuned pipe will tend to run sporadically at partial throttle.

If you have an O.S. Max .61 FX, or can get one with the Alpha .60, then I still say it's the best fit for the Alpha .60. If you have a .46 FX or .46 AX and you're looking for gentle trainer-like flying with mild aerobatics, then this would be a good combination with a standard sport muffler.

If you don't mind some extra nose weight and you really want to wring out the maximum performance of the Alpha .60 airframe, then the Super Tigre .61 or SK .80 would be good choices. You will probably want to try a 13x6 or larger prop on the SK .80 for it to run in it's ideal power band, and if the Alpha .60 doesn't have the ground clearance for such a long prop diameter, you can either buy larger diameter wheels for the airframe, try a 12x6 or 12x8 3 bladed prop (similar in load to a 13x6 or 13x7 2 blade), or both.

If you're going to buy a new engine to put on an Alpha .60 trainer and you want a good combination of power and economy, I'd look at a plain bearing .61 like the O.S. Max .65 LA, the Thunder Tiger GP-61, or the K&B Sportster .65 available from http://www.mecoa.com . These powerful, inexpensive engines will provide very good power and light weight. If you decide to put your Alpha .60 on floats later on and fly it from water (a common fate for many trainer airframes), these engines have no ball bearings to rust if they accidently get dipped in the lake.

The O.S. Max .65 LA actually outturns the .61 FX on a number of props, yet it weighs about the same as the .46 FX or .46 AX. Light weight translates into light wingloading and better glide ratio, which is a good thing on a trainer like the Alpha .60 ARF. The only downside to plain bearing engines like the .65 LA, the GP-61, or the Sportster .65 is that they run best on fuel with plenty of castor oil as part of the lubrication package. If your local hobby store only sells fuel with 100% synthetic oil, you're going to get weak performance and premature wear. Ball bearing engines are generally heavier, but they're less picky about the kind of lubrication with which you run them.

Hopefully, if I haven't gotten any other idea across to you, at least by now you should have a pretty good idea that the Alpha .60 ARF will fly quite well on a wide variety of engines and that which engine in particular that you choose isn't critically important. Rather, each engine represents a trade-off in terms of weight, wing loading, fuel consumption, and price. If you go with an engine at the top end of the size and power scale like the SK .80, you may need to upgrade your wheels and props to assure it runs the best that it can.

Good shopping and good luck!