Erik my handsome there is no difference between B, C & D heads, breathing via a "D" can help but the ones that have been most effective are the the ones with a non return valve of some description, the ball types sound as if a steam engine is running, reed valves are silent, ideally the vapour should pass through a course gauze to remove oil droplets or via a larger chamber so vapour velocity is reduced and droplets fall or the most effective is the breather fed into a round a round chamber "tangentially" so the vapour gets centrifuged to the outer surface and clear vapour goes up the centre via a non return valve (NRV) then this chamber must have a drain on it BUT via a liquid trap with sufficient height that the crankcase pressure will not overcome the trap height. The drain to be lead to a low point of the engine with about six inches (15cm) trap height.
Mr Dyson has made a fortune with (patents in place) his vacuum cleaners using this method yet it was invented in the 1800's to separate water droplets from steam before it left the boiler through "cyclone separators".