Pete:
"I remember a flat crank being used in a SBC in Formula 5000. It sounded really neat, similar to an engine with 180 degree headers, but the harmonics were such that every time the car came back to the pits you had to do a full bolt check! I never heard of the four cylinder having the same problem."
The first time a Cosworth DFV engine was tested in a Mirage sports racer, it shook all the needles off the gauges.
Regards, Neil Tucson, AZ