Sorry; I see what you're referring to now. Those are the new factory windows that do indeed work differently, and don't magnify the view. Guess I'd go back to checkeing pressure.
Doesn't matter if it's mechanical or not, the fuel pump can deliver too much pressure. I've had to install pressure regulators on mechanical fuel pumps also when they ran up around 7.5-8 psi. Holleys don't like it once it gets much over 6 psi.

 

I had an issue with a new 600 Holley. I got it for my old pickup. The secondary needle and seat kept hanging open. It was dumping fuel out of the vent tube. I could hear it trickling when I got out after going somewhere. I would go home and pull the needle assemble out to check for trash, nothing. A good shot of carb cleaner and reset the float and it would go away for a week or so. The same thing. I replaced the needle and seat three times with the same problem. After the first time I thought my fuel filter may have a hole in it so I replaced that too.

I never found out why it was doing that. I got the carb used but in new condition from a guy for $10. I can only guess that there was a defect and thats why he was getting rid of it. LOL I sold it at a yard sale for $50. Hated that carb with a passion. To this day I know if I hadn't had a MSD lighting the fire on the truck I would have been stranded a couple times. The motor eventually gave up after washing down the cylinders on a daily basis.

 

to much fuel pressure would allow fuel to rush in past the float on over flow on take off.
Would it have any other effect?

I'm thinking this idea is worth checking into.
Just don't have a fuel pressure gauge sitting around.

 

Too much pressure will push the needle off the seat, over coming the weight of the float.

 

If it's mechanical the pressure will increase with engine rpm. Since you mentioned it having the issue when you accelerated, I think it might be good to look into. My neighbor had a stock fuel pump on his 350 and kept flooding the engine. I checked pressure and was surprised to see it was nearly 9 lbs.
Installed a Holley regulator/gauge and dialed it down to 5 lbs. and it's been working fine since then.

 

hmm, ok.
I guess I will get a gauge.

Thanks for the idea. Might just get a better fuel pump and a gauge.