I think it's all in how the engines are broken in, and treated afterwards.

I have three Tower 46s, and they are all reliable and powerful, good running engines. The only time I ever had a problem was due to ingesting dirt in an inverted application. It scored the piston/liner, and lost all its crankcase compression. (It was weird- I could hear it flame out when I went vertical, so I'd nose the bird over into a shallow dive, then throttle back to idle and it would relight.) I sent it back to Hobbico and they sold me a new one for $40. My 46s are on: A Lanier Sabre; a GP Kaos; a Hobbico Superstar with GP floats.

The break in procedure is critical. Doing the "pinch test" during runup is critical. I always err on the side of "rich" for the first half dozen or so flights on a new airplane, until I'm sure the engine is not going to go lean on me. One thing I also do during runup is point the nose at the sky with the engine running full power, to make sure it doesn't go lean when vertical. I think most so called "problem engines" are damaged due to running them too lean. Just listen closely at the flying field sometime, you'll see what I mean. If you can't hear a little bit of "crackle" when the airplane is on the ground at full throttle, it's too lean, and when the engine rpm picks up during flight, you'll fry it.

I have an OS 40 LA on a Lanier Shrike, and it's a hoot to fly. Not a lot of power, but not a lot of airplane, either.

I have three Norvels- .049, .061 and .074. All of them are great engines. The .061 has an incredible amount of power for its size and weight. It's going on a Herr Aqua Star.

My only other flying engine is a Magnum 15, which must be on steroids. I have it on a little Heinkel 31 sea plane that acts like a Schneider Cup contender.

I have an OS 10 LA, but have yet to find an airplane with low enough performance to put it on. The Norvel .074 is twice the engine a 10 LA is.