I've stripped the assembly completely, and then finished the cleaning process by removing all the old paint from the outside and all the oil staining from the inside with Nitro-Morse (yep, the stuff you use for stripping paint off your banisters!)
There was one nasty surprise. When removing the clutch and flywheel assembly, the "C" ring and washer that is supposed to retain the primary drive gear on the crankshaft was missing completely! Just not there? It appears this has allowed the gear to move in and out on the end of the crank shaft which in turn has bashed the thrust washer that sits behind the gear into pieces, which are now sitting in the bottom of the sump! Fortunately neither the gear or the crank are damaged, but I wouldn't mind guessing it's what was causing the extra whining noise, as it can't have been meshing properly with the idler gear? Hopefully it hasn't damaged anything in the gearbox. (in Mini's you might know, the gearbox sit's in the sump below the engine, sharing the same oil and in this case the same debris!)
Luckily that was the only surprise. The other - more expected - areas that needed attention were the Main bearing shells, they have been replaced, the bores which needed a flexi hone, and a corresponding new set of piston rings. Oh yes and the cam followers are worn enough to require replacement too.
On the up side, the cam shaft itself is hardly more than run in, and that goes for the big end bearing shells and the timing chain as well. I think this points to the engine having been opened before (this is also evident by the used tab washers throughout). But why someone would replace a cam shaft and not the followers is beyond me? (Although apparently not beyond someone that forgot to fit the 'C' ring and washer on the end of the crank? Enough said). The pistons, now the lacquer has been cleaned off look like new, as do all the other smaller components and covers etc.
I've bought a new oil pump new timing chain tensioning rubber rings and a selection of new nuts and bots as a matter of course.
As you can see in the pictures below, not only has the engine bottom end been stripped, cleaned and inspected, it's actually all back together again and looking resplendent in it's original BMC green engine enamel paint.
Next job is the gearbox, where the strip down is well underway, so I'll update you on that very soon.
Thanks for looking!