[Jack E/NJ]

Old Henry>>>I would wager that if you could measure the vacuum in the air cleaner canister there would be no measurable vacuum, certainly not enough to suck air backwards into the out vent where the airflow is creating much greater vacuum to suck it that way.>>>

And I'll wager there are times and conditions when you are correct, Old Henry. Like coasting fast down a steep hill at no throttle. But there are other times and conditions when you aren't. Like going slowly up a steep hill at high throttle --- and this is when you wish some of the blowby & gases were being directed down the throat of your carb and out the tailpipe. 8^)

Jack E/NJ