[mr0077]

An empirical formula in use in 1966 was L = 120V/N, where L=tuned exhaust length, V=speed of the exhaust pulse (assumed to be 1700 f/s) and N=target RPM for peak power. This works out to a 34" runner length for 6000 RPM.
Bob, do you know what the target RPM for the Cobras was?

FWIW, a Chrysler-developed formula in that same era for tuned intakes was L=72C/N, where L=desired intake length, C=speed of intake pulse (assumed to be 1100 f/s) and N=target RPM for peak power, soooo, for the same 6000 RPM the tuned intake runners would be 13.2".

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