Rumour has it this is how Alpina started the B8 series, with a 4.0 litre M60 V8 tickled up from 286 to 313 BHP. But in order to stay ahead of BMW's own M3 that soon after was given 321 BHP they had to do more. Only 4 or 5 4.0's were built and they all went to Japan. Soon after Alpina developed their own 333 BHP B8 4.6 M60 V8 lump (that was also used by BMW for the X5 4.6i) to be able to beat the M3 again.
Never knew there was a 4.0 version until I ran into some press info (thanks Rob!) that I'm glad to share with you:
looks a bit nose-heavy to me, but definitely a wannahave!! 5 single pieces... if that isn't rare than what is?? knowing those crazy Japs all five of them must have Honda engines by now...
I found a Youtube clip of one on a Japanese racing course. look at the poor driving skills, wobling around in those chicanes
I must say I did think about buying a B8 4.6 as a daily but decided for the M3. I think the B8 is much more fun, only slightly heavier that the S50B32, but I'm still afraid of Nicasil problems and fuel consumption would probably be much worse even compared to the M3. But the bottom end torque of the B8 is amazing and addictive.
The red B8 4.0 prototype in the picture was later converted to B8 4.6 by Alpina before ending up with a collector in Switzerland. Currently the car is on its way to the Netherlands where it may be offered for sale at some point. Nope, not mine!