oil out the dipstick

Blow by... had the same problem with a 340 that i had. Did a lot of street racing with it and then all of a sudden i developed the oil out of the dipstick problem. After i tore it down i discovered that i had busted the land between the rings on one piston. It in turn put all the compression for that cylinder into the crankcase. Saved the block after a .080 overbore. Thats my two cents. Good luck.