Airflow loop to help oil drainback

[Circlotron]

I've heard of some engines that when run at high rpm and high load end up filling the rocker cover(s) with oil because of problems with the oil draining back to the sump. Over supply of oil to the rocker gear and blow by coming up through the same passages the oil is trying to use to return back to the sump. Has anyone tried using some kind of air pump that draws air out of the sump and directs it into the rocker cover, the idea being that as it goes back down to the sump to complete the loop it might also help the oil to flow back there? Of course you would need a pretty good oil separator for where the air exits the sump.

[Tom68]

I've heard of some engines that when run at high rpm and high load end up filling the rocker cover(s) with oil because of problems with the oil draining back to the sump. Over supply of oil to the rocker gear and blow by coming up through the same passages the oil is trying to use to return back to the sump. Has anyone tried using some kind of air pump that draws air out of the sump and directs it into the rocker cover, the idea being that as it goes back down to the sump to complete the loop it might also help the oil to flow back there? Of course you would need a pretty good oil separator for where the air exits the sump.

Shouldn't be any need.
For example, on a SBC, if you try to breathe pre '68 heads through the rocker covers they breathe through the drain backs and blow oil out the breathers, the fix is simple, you drill a 5/16 hole between each pair of pushrods and they work fine.
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[BOOT]

Some people add external head drain(rear)/vent(front) lines, seen either front or rear used. I like to vent from the fuel pump boss area to a catch can with a SBC. A lot of modern heads are more open in the pushrod area or as mention you can open them up some, I used a carbide after drilling a hole in one of my videos https://youtu.be/4QlAn0-1-kU

Also a reason to use a dry-sump or vac pump setup.

[Walter R. Malik]

In some instances, don't put breathers in the rocker covers but, breath the crankcase from the valley.
When blow-by air is forced up the drain-back hole to breath through the covers, oil can not get down through those holes easily..