Crankshafts identification can be confusing as many were converted from the main forgings by British Leyland to produce replacements or alternatives from about 1969 on.

This is evident when a crankshaft has the main forging number machined off and a new number stamped or etched over the original numbers. Part numbers were sometimes allocated using the Stamping number, such as 12G1683 on a 12G1505 forging but then superseded by part number 8G2740. On the 997 Cooper the first crankshafts were oil fed to the primary gear and the part number 12A375 had a forging number 12A375. The later 997 Cooper crankshaft without the oil feed hole for the primary gear had forging number 12A298.

For the 12A375 replacement market the later forging 12A298 was used with the number machined off and 12A376 stamped as identification.

On the original Morris Motors drawings for AEG479 Cooper S 1275cc crankshaft it is stated that they used AEG316 forging and cross drill extra holes before nitriding, but all factory cross drilled S cranks seem to be on AEG480 forgings. The earlier AEG316 forging was indeed cross drilled by enthusiasts and racers. Also on the drawings it shows AEG622 as a crankshaft complete and then AEG623 as a crankshaft in EN17T tuftrided, yet everybody assumed they were EN16 but more to the point is the fact that AEG623 was the part number and AEG622 the stamping number on a 12G1505 forging.

The 12G1505 forging for 1275cc engines has therefore had 2 main bearing thrust washer widths, 1.190-1.191” for Cooper S MK3 block with tappet chest covers and 1.211” wide for all solid wall blocks. Mainly produced with 1.75 big end journals it also had 1.625” journals for Cooper S and early ADO16 variants such as MG,Riley and Wolseley 1300 but with different main bearing thrust washer widths as previously stated.

The 12G1505 forging used for AEG622 Cooper “S” and 12G1817 for the ADO16 1300GT were tuftrided as they used the 11 stud head. 12G1683 which fitted both Mini Clubman 1275GT and ADO16 1275 cars had a small crossover period around the early 70’s where a few were tuftrided for aftermarket or fitment to 1300GT before being replace by part number 8G2740 which was a standard 12G1505 crankshaft.

Part number BHM1385 was a CAM6581 forging with fillet rolled edge for durability and tuftrided was fitted to ERA and MG Metro Turbo. CAM6232 is part number and forging number for the A Plus 1275cc crankshaft also a fillet rolled edge on the journals and were produced outside of Rover by Mitchell Shackleton in Manchester.

Over 900 CAM6232 forgings were also produced in EN40B from 1993 on for the Mini Spares Centre range of performance crankshafts, some are stamped with stroke length or Mini spares part number but mostly with the stamping number machined off where the crankshaft webs have been chamfered and modified to help reduce whip.

All these details are only from crankshafts stocked or handled and identified by Keith Dodd since 1963 to 2011 - Copyright Keith Dodd