I'm a skeptic as well, you'd almost have to be pouring gas down the cylinders to dillute the
oil that much and your eyes would be watering from the excess vapors. I'm also a little leary of the power valve suggestion. I ran a 428CJ with Tri-power for several years and initially getting the carbs set up was frustrating (turned out the carb face where the bowls/metering block attached had been bowed over the years,all three, and didn't allow the power valve chamber to get a good seal and it wouldn't hold the valve closed, after machining flat again it worked great) and although I ate a few sets of plugs my
oil never was that dilluted. As mentioned setting the valve up for your vacuum is almost a neccesity, but that sounds almost like one of the floats was sticking. Most of the time when you install a power valve plug you have to fatten it up also so that will make it richer through the whole rpm range.It's purpose is to allow as lean a jetting as possible while giving extra fuel for acceleration and once you hit steady state cruise it closes again. On the pump up issue, the lifters actually have a small "piston" inside that moves a little to allow no clearance and still allow the valve to close all the way, if they can't bleed off some of the pressure they basically become solid. This holds a valve open until the valve action and
oil pressure gets to a lower rate, sometimes only after the engine is shut down and pressure goes away in extreme cases. I had a 351C that did this after I wound it up to anything over about 4000rpm and it would literally be running on about 5 or 6 cylinders when it dropped back to idle and would miss for a minute or 2 until the pressure dropped down and stabilized. After measuring valve clearance with the lifters collapsed I installed several shorter pushrods (Ford sevice parts) and the problem was gone. The pushrods come in .030+/- length so it doesn't take much.