I covered my blowby tube with my finger and waited about 5 seconds.
When I let go there was some pressure and a small cloud of air/oil.

obviously the engine was running

This seems good to me at 140k?

thanks

karl

 

Sounds good to me.
You need to start worrying when plugging the blowby shoots your dipstick out.

 

Not if you have a locking dipstick

 

On my 97 I had overfilled (I think) my oil and had a blowby problem about 2 years ago and took it to Cummins for a manometer blowby test which it passed fine with about 175K miles on the truck. The mechanic said my engine was barely broke in and doubted a problem...and he was right.

Here are the results for those interested:

1 inch at Idle
8 inch at 2900 RPM (parked...not driven)
Max blowby is 16 inches @ W.O.T.