Sorry for bringing this topic from the dead, but I remember it being here and so didnt want to start a new one -- if I get A+ gears however what changes to 1at motion, laygear etc would I have to make to optimise the gears to a mildly tuned 1275?

If you have an A+ rod change box, the stock ratios are (slightly) worse than a stock rod change. Late Pommie 1275GT gears will convert it to Cooper S ratios but I think cluster gear for that is NLA.
`Cooper Tune Racing' on the MM/MS board is trying to do one, and can't get parts.

Main problem is the layshaft & it's 1st gear end bearing is different, so A+ gears won't fit earlier boxes and vice versa.

I run an S MK2 remote box fitted with the later rod change mainshaft (18mm nose), which is stronger than the stock 14mm one.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Are the ratios on standard A+ : 1st 3.52, 2nd 2.21, 3rd 1.43 and 4th 1.0?

Also awhile ago I was talking to that guy on ebay who was selling a Jack Knight Metro gearset created for the "Metro Challenge" or something and he claimed that A+ gears are interchngable with B series gears???

I don't have the A+ ratios handy at the moment...
Helix angle was changed (made steeper) for the A+, so a whole set of gears would be needed. Gear centres in the boxes are the same. Problem is, the 1st gear end of the A+ layshaft, and the cluster gear bearing at that end are both different to normal rod change/4 synchro remote ones.

I'll stick to 4 synchro remote and A series rod change, there are still more parts available either new or s/h.

I've been told the Metro Challenge gearset even in UK is like rocking horse droppings... and s/h ones for sale are probably worn out.
at least you can still buy the normal A series SCCR gearset new, easily from MiniSpares or elsewhere, for around A$1,100..

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.