Hi Mike, I have never been around a BN1 or 2, but I believe they have road draft tubes. And should have a vented cap on the valve cover. This would be the most ideal arrangement in leu of not having an enclosed crankcase at all.
.....! You'll note that on the 3000's the tee at the top of the valve cover with the hose going to the rear carb and the other side of the tee going to the lifter side cover, the hose going to the rear carb is acting as a two way street allowing air to move into and out of the crankcase. This is not an ideal situation because in reality there is very little circulation. Just venting and not very efficient. If a BN1 is running with a non-vented valvecover cap, it's crankcase ventilation would be about as good or better than an original spec 3000 because the crankcase would be able to be vented by the road draft tube on the lifter side cover which I would suspect would have less restriction than the original spec 3000 engine. With a vented cap the BN1 would have a very traditional and adequate crankcase ventilation. With a non-vented cap it would be not so good but with an open road draft tube at least it would have a vent.
When I put the engine back in my BJ7 recently I decided to change the crankcase ventilation system just alittle bit. I removed the hose between the tee at the top of the valvecover and the rear carb and installed a small K & N filter on the tee end. Ever since I did that I have had no drip from my rear main seal as is traditional for our LBC marking their territory. Dave C.