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Message: <blockquote data-quote="Dave_J" data-source="post: 98036" data-attributes="member: 3169">In the restrictor plate used in Nascar, the carb is much larger than the plates holes, and as is the runners down to the head. This plate is a CHOKE, not a venturi. It allows only so much air to flow no matter the carb or runner size. But the engine builders have found out that it does cause the air to speed up and causes some turbulence and they have tweeked the runners so the velocity is higher and they make good power. A second venturi down in the runner could be used as an airflow choke, it will work. The airflow before the venturi may stall some. It will speed up only thru the venturi but as soon as it gets to the larger pipe section it has to slow down again and may stall out some again. But making the pipe size the same end to end, but smaller works better in prior race car tests. The Chevy Vortec engine has a venturi down near the valve just to cause a vortex/swirl in the combustion chamber. If the carb has a removable booster ventury on the top, adding a coating of epoxy to thicken it up will make the carb air flow smaller.</blockquote>