The Milwaukee 8 is not and never was a racing motor. It is an evolution of the traditional Harley V-twin. The Twin Cam it replaces was a evolution from the Evo and so on all the way back to the Knucklehead. As a result of more efficient combustion and relocation of the catalytic converter the exhaust temps were lowered by 100 degrees.
The last Harley motor with 4 valves per cylinder was the V-Rod, before that the only 8 valve motor Harley produced was the 1916 Model 17 racing motorcycle.