Carbon build up around valves ?

[PRTVR]

Anybody found any when stripping down the heads?.

I know that the way they are normally driven this shouldn't happen.
I was thinking with the way these engines are built they could be a chance of oil getting into the combustion chamber and causing it.
Second question How much slack could the hydraulic lifters take up ? would a small amount on the valves lead to the dreaded tick and then perhaps a pad may come of leading to premature cam wear due to there being slack in the system.
Below is what started me thinking about this.

http://www.mini2.com/forum/second-generation-fault...
This same problem happened to a friends car a Mini 2.