next week i have to do a presentation on the materials and manufacture of the A series crank, conrods and pistons! if anyone know about the exact steels and manufacuring methods of the OEM and uprated part is apreciated, cheers
All standard cranks are forged, only some custom or rare replacement (eg short stroke) aftermarket versions are billet machining. The most common material for the A series crank is EN-16T. Early ( early 850 A series, Cooper small block etc) examples may have been different, records are up to the usual Leyland standard.
All the big block Cooper S’ (970, 1071, 1275) had an EN-40B crank, the 1275 version of which was nitrided (short strokes may have been also) and some 1275’s were cross drilled as standard. All of this is except (there’s always an exception!) for the very last Mk3 Cooper S 1275 which had a tuftrided version of the standard EN-16T 1275 crank common to all non S 1275’s (cost cutting). It is possible the 1275GT version was also tuftrided from this EN-16T specification.
I am sure you already know that the early (Cooper S and other marques)big block motors ran the 1 5/8" big end bearings but later engines changed this to 1 3/4"
All A+ motors used an EN-16T crank. This crank has greater strength and stiffness than the earlier EN-16T item due to a change in machining detail at the root of the journals, being rolled rather than cut where they join the webs. This change may have been incorporated earlier than A+(again, great record keeping). Early MG Metro Turbo’s used this same crank with no modifications, but fairly soon they started to get a heat treated unit. The treatment may be Nitro-carburising, but may not.
All I know about con-rods is that Cooper S ones were EN-24V.
This is data I have got from many sources over some time, and I can’t be certain about all of it, but it is all I have.
aw cheers that great exactly what i was after, you a life saver dan!
Wow, could you have got a better answer!?!?!
Nice one Dan!
