What do you mean by "carb boxes"? The bowls on the bottom of each carb? If so, they are easier than the top caps, under the top caps are rubber diaphrams that need to be seated perfectly so the slides rise and fall as they should. The bowls house the floats and stay in place when the bowl is dropped as long as the float pin stays in place. The screws strip easily so you may want to remove the carbs to do it, you don't have to just might make it easier for you. If you strip one needlenose vise grips can be used to get them out. Take one to the hardware store and get stainless allen head screws to avoid that issue in the future.

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