Our product picks are editor-tested, expert-approved. We may earn a commission through links on our site. This 750iL has a custom exhaust and a six-speed swap. It's just about perfect. BMW's M70 engine was the company's first V-12. Essentially two of its straight-sixes mated to one crankshaft, it displaced 5.0-liters and made nearly 300 horsepower when it debuted in the 1980s.