I've built a half vw engine for a legal eagle and it also blew oil out the breather and dipstick tube... and everywhere else.
I discovered that some of the guys had a one way valve in the breather that only allows air out. After building one
(simple flapper valve) and installing it on the breather (generator stand) port, problem solved. The four cylinder
vw doesn't leak because it has two pistons moving out of the crankcase at the same time that the other two are moving
in. Half vw's have only two that move both in or out at the same time. This forces the air out the breather on the in
stroke and then sucking it back in on the out stroke. I bet the valve will fix your problem. Now my crankcase runs with
a slight vacuum when the engine runs.... if it leaks oil now, it has to be after the engine is stopped. If you want pictures of my valve I have them....Good luck!
John.email@example.com (John Orr)