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MG Midget and Sprite Technical - 948 Red 406 Cranks

Can anyone shine some light on what material C-AEA-406 'Red' cranks were made from?
These were available from ST and are marked 407 not 406. They are not to be confused with the AEA-461 Formula Junior crank which was different and made from EN40B. The 406 was made for the 948 engine.
ST manuals/parts list does not state material, Visards book suggests they are EN40B but I think this is incorrect as the one I have is not hard enough to me that.
Any info would be of help.

Paul N-M
P A P Neil-MacLachlan

Snapshot from "C-AKD 1021 C" Special tuning for the midget and sprite 948cc

See pic

Not much help either I see now

Alex G Matla

Thanks Alex, but yes info I already have and not much help re material spec.

P A P Neil-MacLachlan

Having an insight into 60's tuning practice I would suspect that Special Tuning had a batch of cranks made from standard material which were then Nitrided for competition use... but I'm sorry I don't know.

You might want to talk to Nick Swift, Bill Richards or possibly Richard Longman (if you can find him) - they are the only people I can think of who might know the answer.

John Faux used to build some tasty 950 engines for Ian Burgin's FISC car so he might know as well.


James Bilsland

In a A series tuning book by J.H.Haynes dates 1965 he only notes it 'being made from a high quality steel will allow 6700 rpm continuously, and 7200 rpm momentarily. For higher revs then BMC F.J crankshaft must be fitted.'

All I could find - having broken cranks in the day and never being able to find/afford a red crank !

richard boobier

Similar to what Geoffrey Healey says in 'More Healeys'.
Dave O'Neill2

Never saw a BMC crank that didn't have the material stamped on, not saying they don't exist.

"are marked 407 not 406" Parts were designed and numbered, then the forging or casting was derived from that drawing and got the next number. This is common with BMC parts. Sometimes later variants used the same forging (or casting) blank, but were machined differently, so you could have a part marked 407 but with a part number out of sequence, as AEB3902, as a made up example. Some parts blanks are marked as XXX123 R/L, but when machined to hand become XXX124 or XXX125; presumably the "concept" part drawing was XXX122.

FR Millmore

This thread was discussed between 27/09/2012 and 04/10/2012

MG Midget and Sprite Technical index

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