If anything, the small ports and smaller-venturi carburetor will make the engine more responsive at low to moderate speeds. You'll lose a little top-end horsepower and RPM, but unless you're planning to run full throttle most of the time, you're not likely to see a major loss of performance. The carburetor might need to be re-jetted slightly leaner to compensate for the higher velocity through the venturi at any specific RPM.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!