When it runs for 10 minutes, no smoke engine sounds fine, if valves are problem it would have to have self-adjusted, and I would think if anything looser from wear rather than too tight. We have not opened up the engine....
Not valve trains.
They tighten as they wear believe it or not and can very well hold valves open when they warm up and parts expand.
I won't be offended if you want to ask about that in your thread.:D