oooh, i didnt use that,Dave, most 1275's don't have tappet covers anyway. Only Cooper S 1275 blocks do. The breathing on 1275 blocks is from the timing cover and the clutch housing and you will need to vent the timing cover when you build a 1275, as well as the other end. If you don't the timing chest pressurizes and the crank oil seal will fail very early. I run with both the tappet covers blanked off on my 998 and a breather in the timing cover and clutch housing as 1275's have. Keeps it all nice and oil tight.
PCV valves haven't been in use on Mini's for decades.
The oil filler cap is also part of the breathing system, as that's where the fresh air comes into the engine from. That's why you have to change it as part of the service schedule.
And surely they use PCV's, most 'modern' vehicles do... :-S don't they?
Sure they do, we used to replace them with out blow-by meters on the test engines...