This issue has been bugging me for years.

Did one of the guys racing Mustangs back in '66-67, re engine his car with a flat plane crank motor? I can't recall the exact meeting, but one of the Mustangs - white with stripes, I'm sure , had an engine that sounded decidedly different - more like a straight eight (think Bugatti-ish). It wasn't Fahey - could have been Coppins. The announcer said he was running a flat plane crank in his engine!
At the time, I thought "Oh yeah, that's interesting", but thought little more about it. When Yamaha put a flat plane crank in the R1, it re-awakened the niggle.

Anyone?