Aha ..... this old Landy has a British Leyland emission control valve doo-dah, that feeds crankcase fumes to BELOW the carb, or sometimes to a stup pipe ON the carb but below the butterfly valve..
My bet is that this engine USED TO HAVE, but DOES NOT NOW HAVE, the fumes control device fitted to the top of the rocker cover, or if it does have it that it is buggered or jammed wide open.
Quite simply far too much AIR is passing up through the BREATHER system, along with OIL vapour and droplets and crappy fumes.
One immediate solution is to feed the breather pipe into the air flow BEFORE the carb (above the carb), instead of AFTER it as at present. Whatever, you MUST vent those fumes away from the engine. MUST .... OK ??? Or else ....
You could have a look at the breather thing, and if is the right one, clean it properly.
As I recall it should look like flat-topped mushroom, about three inches across, with an inlet pipe stub from the rocker cover like the stem, and a black hose to the carb or manifold.
I think in most of them, but not all, the flat top unclips for access to clean them. Take care to put it back the right way!
CharlesY