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1.) A carb spacer can be for different reasons. The original phenolic resin spacer was to insulate the carb from engine heat helping to reduce fuel percolation in the float bowl.

2.) Sometimes a spacer is added to increase the plenum volumn in the intake manifold. It depends on how your engine is set up as to whether a spacer helps or hurts perfomance. There are numerous designs and heights available. Also it can lead to hood clearance problems.

3.) They are relatively inexpensive, so it won't hurt to try one even if it doesn't help.

4.) The hose to your valve cover is for the PCV valve. You need that to pass almost any vehicle inspection in any state. Most aftermarket 4 bbl carbs have a vacuum connection for that application. Otherwise you can run that hose directly to the intake manifold. You really need a PCV valve anyway just to get the blow-by gases out of the crankcase.

Rev