Marcus,

I don't have any info on your specific questions, but I am familiar with the 46FX. It is a pretty large and hefty engine, and was designed for mid-high RPM RC use. The current OS AX's developed from the FX's. I don't know if there was a problem the AX's were supposed to fix, or it was just marketing to introduce a different look...

Worked a project for a friend about a decade ago, to break-in and diesel convert OS 46FX engines. DDD conversion heads and fuel, Stock and Perry carbs tested. Larger props than engine was intended for, to use the torque promise of diesel operation and fuel.

General impression of the 46FX: Very easy to work with. Very flexible to conditions. Break-in was initally on glow fuel. As with most good OS engines, first few starts were slow in coming. After the exhaust cleaned up - early runs shed dark residue as fits polish in - economy and handling improved.

Each of the dozen or so I dealt with ran similarly, early break-in experience near identical. It was surprisingly docile with the larger props, and pretty economical as diesel-converted. Seem to remember RPM around 10,000 on 13-6 props and good throttle response.

Not much of this is directly relevant to CL conversion, CLPA in particular, but the 46FX is sturdy, consistent and easy to work with. As a glow, it would probably prefer to run faster than 9-11,000 RPM. With the best plug, fuel, prop, load and setting, it would probably be comparable to a strong .50-ish engine.

One negative might be finding replacement parts in event of wear or crash damage.

Marcus, two things here.

One, your engine test mount is verging on unsafe as it has no retention pins to stop the engine from launching forwards if those (rather small) clamps worked loose.

And two, where is the muffler mate? You aren't going to get a feel for an engine minus its compulsory muffler, so of course its going to be a bit wild.