Here is a video I shot back in the 470 dyno test days. I don't think I've posted this one before where you can watch the valve cover fill up with oil as the RPM goes up.
https://www.youtube.com/watch?v=8oLyIhDdKww

Oil restrictors. That's oil that should be on the crank.

Can't really see the oil level rising, maybe my fault or I need new glasses.

It'd be a good test for a Hemi, given the internet folklore of "each valve cover holds a gallon of oil at high rpm" or whatever it is this week.

Dave V. sent me some valve covers that are too wide to fit most passenger vehicles, but would work on a dyno, and are nice and flat for
opening up and creating a couple picture windows, above and below the spark plugs for a similar test. Hmm, maybe they'd be good for that type of project.

Yeah I'm not sure how much oil was actually trapped in the valve covers in these tests, you can see it coat the bottom of the Lexan window but you can't see anything else. This was a wet sump engine. I have videos of a dry sump engine and it does the same thing. The rocker arms throw off so much oil at WOT that even the dry sump can't suck it all back into the tank.

i wonder if a window in the oil pan sump would tell anything worthwhile ?

Been there, done that and have the pictures to prove it.

Windows and/or various styles of sight glasses and sight tubes in oil pans have been used for many years for this kind of testing.

A sight tube can give a more solid view of how much liquid oil is really there, without struggling to see through a hurricane.

B1 motors are famous for that, even with additional #8 AN drain hoses added on each end of both heads
My next B1 motor will have #10 AN drain back from each end of both heads to help keep the oil in the oil pan quicker: luck:

what kind of info did you learn from doing that ?

if one were to make up a sight tube, what size of tubing would be best, and what material would one use that wouldn't cloud or degrade over time ?
where would be the best place to install the sight tube ?
what type of fittings would be the best to use ?

Nothing really. Once the engine fires up the window is covered with oil so you can't see anything. We put a sight tube on the dry sump tank and that was very interesting. Once we had a sight tube on the dry sump tank we could tell how well the system was working.

would that be seeing [on the sight tube] how well the oil drains back to the sump/tank ?
sorry if i seem like a real dummy Andy.

Just goes to show you can get away with a very small restrictor for top end oiling.

A window in the pan might help some IF it was on the other side of the pan than the one pictured. On the pass side its going to get covered as soon as you fire it up and the crank will be slinging any oil there that direction. Oil control and oil in suspension from the lack of control at the crank are big issues with a BBM for sure.

That is all I could see as well. It is interesting to see at least something in the valve cover for info.