400i Alternator and ignition timing

Hi Guys,
The top alternator in my 84 400i failed recently, the warning light illuminated with the ignition off and key out, and went out with the key turned ready to start(when the light for the lower unit came on as it should).
Is this something that could be repaired, or am I better off with a new alternator. If its a new one, is there another source other than ferrari, I am in London UK.
Next, I have set the ignition timing to the stock 8degrees BTDC and the car runs smooth, but if I advance it a bit I get more power all round. I am using 100 octane fuel and get no pre detonation , has anyone got any info on how much advance you can use. The car is an auto, so the engine never really labours as it could with a manual, so it is difficult for me to assess if it is pinking or not.
Regards,
Tim.

Timthetooth,

I've had good luck with my 'local shop" tackling alternator repair/rebuild.. a good shop is a good shop.

Depending on year it is a Bosch or other well known vendor......this will keep the costs down.

No answer on the timing issue but I'm sure some others will chime in....

Welcome!