These plates provide restriction and also atomize the fuel/air mix better for greater fuel economy. Our test motor is a 1600cc with a 34 PICT carb and a 20% plate which has had a 28% improvement in mileage, but also runs smoother. Milease has increased by 90 miles per tank. As these plates restrict air flow, there is less vacuum to draw fuel through the main jet. Consequently you will have to increase the main jet size to maintain adequate fuel delivery. We have found that a 20% plate requires approximately at 1/2 full jet size increase, i.e., 120 to 125; a 30% requires a 3/4 full size increase, i.e., 120 to 127.5; and the 40% a full size increase, i.e., 120 to 130. These are ballpark figures and a less restrictive exhaust system may require more jetting. |