Jap units typically produce 14.4 volts compared with Marelli's 12.5-13.0v and Bosch's steady 13.2v
All car altrenators should give about 14.2 to 14.4 volts. If you have anything less that 13.8V or more than 15V then you have a fault.
Not all Bosch units have the 8mm bolt. The reduction in bolt size is something introduced to all alternators on later models. Your Bosch unit must be intended for a later model car.
yes that's what I thought! voltage drops are the main issues on a beta to bad connections/earths
The output voltage of both my Marelli and Bosch wawere measured on a dedicated test bench while loaded at 25 amps and in my experience (10 years in autoelectrics in the 80's to 90's), Marelli units such as the one fitted to my Lancia and other Fiat group products of a similar age were normally only capable of putting out little above battery voltage.
The Bosch units provided higher output, but never matched that of Japanese units.
Regarding voltage drop, the charging voltage on my car, when I checked it, was measured at the battery terminals and all assocaited charging circuitry was replaced and upgraded to a minimum of 10 sq. mm cable by me when I recomissioned the car five years ago.
As for the age of the 8mm bolt, they were fitted on both my facelift (1979) Betas which leads me to beleive this was period-correct.