In the end, I decided to forego the hinged plates - I would loved to have put them in, but the curved section is there because the oil pickup actually snugs into it, so there's no straight line anywhere that a hinged part could close against.
What I did was to cut a series of roughly 1/4" vertical slots between the pan extension & the original pan area - they should (hopefully) slow the oil surge some, but still allow the oil to flow back into the main tank. I also drilled a couple of 11/4" holes in the very top of the shallow area of the original pan (that now has the extension under it). It occurred to me that, without these holes, the new section of the pan could end up like an inverted glass pushed down into water - the air needs to be able to escape for the oil to be able to fill the extension area. So, I've basically put a couple of small holes in the bottom of the glass...
I tried the dipstick, and it was encouraging. I won't have to modify it at all (which was my plan), and it will still represent the appropriate oil level in the sump. And, I'm even less concerned about oil surge, now - Ford's intended level of oil in the sump indicates that the entire metal portion of the sump will be full, up to the level of the alloy splash pan above it. The splash pan itself has baffling & surge restrictions too, so I think the current plan should work.
I cut the original drain plug area out of the old bottom of the pan for re-use (basically, moving it up 1.75"). The female portion of the drain is a threaded collar, formed on a small steel plate, and attached to the pan with a couple of spot welds. Initially, I tried drilling out the spot welds to remove the collar - it turns out that the spot welds are far harder than my titanium-nitride drill bits (it only took me 3 drill bits destroyed to figure this out -
). In the end, I used the angry grinder to remove the traces of the original pan from the collar & free up the spot weld holes. As there is still a nice flat area of the pan above the original drain hole, I drilled a new hole, fit the drain plug through it & into the collar, and plug welded the collar (through the spot weld holes) into place.
I'm hopeful there won't be any leaks - thankfully, the OEM drain plug's mating surface has a generous O-ring set into it, which should account for any tiny less-than-flat parts of the new sealing area (thanks, Ford - I appreciate that!).
Today, I'm hoping to find some 12 to 14 gauge steel so I can make a new pan floor. I'm going to try my local welding shop, as the round trip to the only supplier of sheet metal is more than 1 1/2 hours.
By the way - as I said, I have about 2-3 mm clearance between the (new) bottom of the pan & the (newly-trimmed) oil pickup snout. Does that seem like enough clearance?
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