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I've come across a motor that was used in a Mk2 998 Cooper "upgrade" back in the day. The block has the 1275 S casting number AEG312 but also has S 1071 stamped into the blanked off area where the mechanical fuel pump would later be situated. There is no aluminium tag on the back that says 1275 or 1070. The motor appears to have been fitted with the Mk2 Cooper's engine number on a home made tag (9FA-SA-H509**).

A few questions about this:

1)Was the AEG312 block ever factory fitted in a 1071 S?
2) What do you make of the engine number? The Cooper bible seems to suggest it is a bit high to be a Mk2 998 Cooper. Am I right? It is a home made tag, so I suppose there could be a typo.

It is also fitted with a 22A1288 gearbox casing and with Hardy Spicer driveshafts.

Thanks in advance

AEG 312 1071 blocks were a factory replacement item when all the AEG151 blocks were used up, my car had one fitted when I bought it. If you look at a 1275 312 block you can see they must have added a spacer to the short block casting process to create the tall block, so the 1275 block ends up with a very thick top deck which is machined down to suit 970/1071 blocks. If its a genuine BMC replacement block the head stud holes will be the correct depth of approx. 22mm and there should be the piston size diamond symbols visible. If its a 1275 block skimmed down its probably had the threaded part of the stud shortened to suit.