I bought a used 05 mcs engine to replace my locked up block . When I pulled the head there was aluminum shavings on top if the piston in cyc 2 . They're non magnetic so definitely aluminum . Looking at the head and valves I can't see anywhere they could have come from. I bought this from a junk yard with intake attached so intake ports weren't open but exhaust was .

 

I would return the engine.

 

Is there a timesert (thread inserts) on the spark plug threads?

 

No there isn't