Theres a non-return valve on the breather you need to remove, pull the breather pipe out and cut the end off the metal part that pushes in. I did this after my engine fitted with twin forties sprayed oil all over the place mostly from the top though. All I've done is vent to atmoshere through a small filter you could also fit a seperater tank if you wanted. I wouldn't put the breather into the front of the carbs you'll suck all that gunk through the carbs which could make a nice grinding paste, it should be connected after the carbs.
Also I've just fixed an oil leak on my car which I couldn't trace, oil was leaking low at the front, I found the fuel pump had worked loose.
Goodluck
Jez