thoughts on polishing engine parts...

[SVXMAN2001]

I've seen a number of threads in the past couple of weeks with members having polished various aluminum engine parts (A/C parts, valve covers, etc..), I was thinking of doing this myself, to include the cylinder head and block, however, my concern is will this affect the mating surfaces of each? Meaning will this interfere with the knock sensors, proper sealing of the valve covers to the cylinder head? I wouldn't be messing with the head gasket surfaces of the block and head, just the top areas primarily. Thoughts? advice? Thanks in advance, Chris