Here are flow bench results from a stock WT257/488 compared to the modified WT257. As you
can see modifying this carb does almost no good. In fact it hurts performance because when you open up the venturi, it reduces velocity. The restriction in these carbs are at the butterfly, not at the venturi. That is why this type of modification is useless. The only thing it does is it looks racy and it makes you think it must go faster. Dyno results have also shown a loss of horsepower by doing this.
On the other hand, modifying a WYK33 does give you a large increase in airflow. It also will reduce the velocity but there is a power increase because of the gain in the airflow. Not all combinations of engines will benefit from this carburetor. Call us and we will be happy to discuss with you what you want to put it on and whether we think it would help or hurt you.