Sure, a 502 BBC isn't a lawnmower engine, but this is a good chart, showing that tuning for 2-3-4th wave can alter a torque curve, a LOT
How much efficiency could be recovered with better intake tuning?
Back in 1964, Dr. Blair replaced pages of calculations with a simple formula for intake pipe length:
L = (1100 x S)/N
L = Length of intake tract from bellmouth to intake valve seat.
N = Engine r.p.m. in the middle of the normal power range.
S = number of crankshaft degrees after bottom dead center that the intake valve closes (up to a maximum of 75 degrees).
Using this formula on a variety of early '60s engines, Dr. Blair arrived at projected intake tract lengths ranging from 14.3 inches to 22.5 inches.
A more recent method reported by Julian Edgar in 21st Century Performance focused on reflected pulse intervals:
Second pulse length (inches) = 108,000 divided by r.p.m.
Third pulse length (inches) = 97,000 divided by r.p.m.
Fourth pulse length (inches) = 74,000 divided by r.p.m.
Fifth pulse length (inches) = 54,000 divided by r.p.m.