Join Date: Jan 2000
Location: San Diego, CA
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Re: Dp vs. vacuum carbs
True, but the vacuum port is located a bit down the barrel past the venturi. It needs manifold vacuum or a serious amount of flow past the venturi to generate a significant vacuum to open the secondarys. In either condition the seconderies should have already have been engaged.
True, a Dbl will be down at wide open @ low R's, but that is its ONLY drawback, and it is easily cured with foot control. Also the secondaries have an enrichment circuit, and a power valve to help control fuel mixture at variable vacuum/rpm/opening rate conditions.
A vacuum carb relies on vacuum to control these conditions, an easy cure, but at a cost in power, especially accelerating.