In a 567, the governor has (using my layperson terms) an 'upper and lower chamber'. Fill cap is in the top chamber. Site glass appears to register level of lower chamber.

Question: are there any adverse consequences to over-filling (added about 1/2 quart)? I'm not talking about oil coming out of the fill cap, but just in general. Level in site glass wasn't visible to begin with. Sight glass is even leaking (oozing) a tad.

If you fill the governor above the sight glass it will weep out of the orifice in the top of the sight glass and run down on the gearbox cover. The orifice is there to provide an equaliztion to atmosphere so the oil seeks its own level.

Thanks, Mike!

So is this a bad situation, or a self-correcting, not a big deal situation?
I ask this because I am wanting to understand how these work.

The governor oil should be half glass when the engine is running. Too much can sometimes cause issues.
Have seen where crews overfilled the governor and engine not loading properly.

If I remember correctly, and I may not, didn't Maier-Mattern valve gear tend to lock up if overfilled? If the actuating pistons in the governor mechanism cannot retract properly after reaching full extension... there might indeed be issues.