The trouble experienced by Cholmondeley Tapper on his blown Type 37 Bugatti — the loss of oil through the breather – still happens! My son cured it by lengthening the breather pipe by about a foot. It is due obviously to gas leaking past piston rings, no doubt accentuated by the positive pressure, and the inadequate breather on the standard engine. The unblown engine has an additional breather through the oil filler, and the 8-cylinder cars have more passages. It has never been clear how the works cars managed!
I understand the modern theory is that gas-flow past piston rings is due, at least in part, to ring flutter. In the case of a Bugatti, it is probably due to large clearances and the bores not staying truly round.
H. G. CONWAY London