I have used a lot of carbs that big on engines that size and occasionally even smaller----it takes a few different approaches to idle air, transfer slot mods, accel pump and nozzle choices, selection of power valves and also a very fine tuned distributer advance mechanism. They can start good, idle fine and give decent milage as you will mostly be on the primaries without tipping into the up tuned seconary side except when you have some open road ahead of you!!!