The BMW M8 that never was...

[danidmas]

Unlike Mercedes-Benz  which produces AMG badged versions of just about every model in its lineup, BMW has maintained greater exclusivity with the M badge. Until last year's launch of the X6 M and X5 M, there have only been four M models (not counting the M1), but one M got as far as prototyping and testing, but never produced: The M8.

Powered by a 550 horsepower version of BMW's original M70 V12 engine, the M8 was meant to challenge the Ferrari 456 GT. However, following testing of the single prototype, BMW canceled the program and built the 375 hp 850CSi instead. The M8 prototype was long thought to have been crushed, but it turns out that it was stashed away in a corner and turned up in the BMW museum in Munich. Check out the BMW Blog for more shots.

Link: Autoblog

550hp 15 years ago was quite something, considering the Audi S6 only had 340. Too bad it never got the green light.

[sentra_dude]

Whoa, freaking sweet! 550hp is quite something now, but back then, damn, that's crushing. I wonder why they didn't build this beast, it would have been a classic if they had!

[bmuller]

I wonder what their motivation was for not building it...

[ARMAN]

Used in McLaren F1 (Was originally developed for M8) (627 hp)

[sentra_dude]

Used in McLaren F1 (Was originally developed for M8) (627 hp)

Sort of...

The S70/2 is the engine used in the F1, and while it was developed from the M70 they are two different engines. The S70/2 would have been far too expensive to put in even the top of the line ///M car since it would have cost more than the car itself. 

I'm lazy so I just cut and pasted from Wikipedia:

The S70/2 was a complete redesign from M70 with no common parts, featuring a lighter and smaller engine block.

I could be wrong but I also think the M70 lacked VANOS, which the S70/2 had.