I have a Evolution 46 problem, however, I believe my question is of a general nature.

I bought this engine new back in May and have run about 5 gallons of fuel through it. This is my first engine.

As of lately, it has started to act up. There is a rattling noise coming from the engine especially when flying fast at full throttle.
I have had several people at the field take a look at it, but none of the suggestions seem to be the cause of the problem.

Another clue to this is that the engine has always left a black residue on the plane after each flight. Not knowing better, I thought this was normal, but a seasoned guy at the field told me this was not so. It might due this for the first few flights while the engine breaks in, but this has not been my case.

I just took the engine apart and here are my observations:

1. The inside of the back plate is scratched in a circular pattern. Looks like the connecting rod is rubbing against it. This could not possible be normal??
2. There seem to be a lot of play in the crankshaft when the piston is at TDC. i.e. the piston is not moving at all, but I can rotate the propeller ca. 35-40 degrees. Is this normal?

What else should I look for to figure out why the engine is rattling and deposits this black residue after each flight??
Also, I have balanced all my propellers.

Is there anything I can fix?

Thanks for any help.