I've been working on my WW2 ABC OHV flat twin for some weeks now - this is the one I bought off ePay a couple of months ago. Frankly, I've never worked on an engine that needed so much doing to it as it showing every sign of having been underwater at some time. It is also many years since it ran, the sump separate & full of dry leaves & crud.
The pistons were seized, both sides. The barrels are steel & turned from solid, so whilst the bores polish like glass, they also rust pit very easily & I was lucky that I had a spare pair of barrels & pistons. Even the spares were a bit pitted, but I'm not intending to race it, after all. An inlet valve was seized, all four tappets were solid, the crank was stiff to turn & I suspect that the mains have suffered although it turns smoothly enough ATM. The rear main is quite irreplaceable - a great big thing with tiny balls that the crank passes through on assembly - so whatever it's like, I'm going to have to live with it. Small and big ends are plain shell bearings, so they should be OK.
The snaily coils of the ducted fan cowlings were difficult to get off, paper thin in places & needed filling to get back to a reasonable finish. Ford Metallic Silver is a very good match for lacquered brushed aluminium & once sprayed up, they look pretty good.
The tappets took a bit of freeing up as they'd corroded into their honed bores. Did it in the end though. The valves have a cap on top & one of them didn't fit - of course it didn't! A diamond drilly thing in a very small Dremelish (I have three, an big Axminster that will take on anything you like to throw at it, a battery powered intermediate that is the one I use most often & the skinny little thing I just bought from Aldi for a tenner. As much as anything, it is a cheap way of getting the bits!)
Aside from the steel barrels & bronze heads, everything is aluminium & everything was corroded. Gradually, I've cleaned the bits & pieces, reassembled the many, many 1/16" nuts & bolts (each nut with the correct washers under it). Today, it was the starter shaft, its four camming rollers and its unaccountable stiffness. It was bent! How anything so short (under three inches) and well supported could get bent I can't imagine, but there you go. I had more wit than try to straighten it & after a good deal of careful work with a file & emery, it turns smoothly enough now. I'd earlier dropped the recoil starter drum - which of course flew to bits with a gleeful "sproing!" and the ten foot clock-type spring leapt out to try & get me - swine. I got it back in second go, but it lurks there waiting my attempts to fit it.
The sump needed a good wire brushing, both by hand & with a brass cup brush. I managed to get out the seized giant sump plug with its two magnets and cleaned the inside of the sump with white spirit & then washing fluid. Allow to soak while I had tea, then boiling water & a brush got rid of the nasty slimy goo that now lurked within. These sumps are cast aluminium & are two separate containers. The one at the front is the wet sump for the engine, the aft one contains the oil for the ancillary gearbox, the pumps & compressors. Some joyless bastard had hacked off the rear sump - a fate shared by many of these units when they loose their generators as they look so odd without it. I spent some time cleaning up the rough work & it actually doesn't look too bad at all now.
There is a flanged thingy secured with - of course - eight studs full of spring & flat washers & a special thin nuts. It is the plate that supports the oil non-return valve and pick up pipe. The spring & ball were rusty, but it didn't disintegrate or run off under the bench, so after an hour's work, they went back in. A cereal packet, a ball pein hammer & blue Hylomar saw to gaskets for the non-return valve plate & the two inlet pipes that bolt to the sides of the sump. I now need two right angle bend rubber/plastic pipes to connect the induction manifolds to the heads.
I have a carb for it - not the right one, they are in a dreadfully exposed position & the one that was on there was broken as usual - but it is the correct bore, so might work quite well.
Tomorrow, the oil gear pump needs to be stripped - they have a reputation for tricksy oiling - and then I'll fit the sump. My though is to "run it in" on the lathe for an hour or two, get the oil round, free things up etc.
The magneto has been on the front room radiator for the last two months, so might have recovered its insulation by now.
I'm not going to say I might have it going for Astle Park as the Beautiful Ones may be listening .........