The window was reworked to properly time the breather by the original builder.

This issue came up out of nowhere.

No work was recently performed prior to the appearance of the oil spewing out the breather.

 

If she was running and no work done do a cylinder leak down test and listen closely to the oil bag with the cap off and the breather hose . Make sure you it TDC on the compression stroke for each hole when test it , you hear a lot of air in the oil bag you have some busted rings or the gapes lined up seen that a number of times it will blow by pretty good . Worse case a wrist pin keeper popped on you .