My reason for using a spacer, specifically an open spacer, is to allow all cylinders access to all for barrels of the carb. Since the stock intake manifold is a dual plane manifold, each set of cylinders only had access to basically a 2 barrel carb. By adding an open spacer I have allowed access to all four barrels to the entire motor. Thereby improving efficiency. The spacer did fit perfectly, only difficulty was bending both the steel vacuum line for the brake booster and the steel fuel line. I noticed an obvious increase in throttle response, and that the elky gets up to speed quite a bit faster. What I have yet to test is how it has effected my fuel economy.