how can I adjust the Butterfly valve to increase power torque?

 

Are you refering to the butterfly valve in the throttle body? The answer is NO. The only adjustment is for idle speed. You could repalce it with a different size. However it's size is optimized for the stock heads, displacement & piston size (bore & stroke) If you change one of these you might consider a large throttle body. Quite simply, the valve is sized for the correct air flow rate at max RPM. There is almost a direct corelation between peak horsepower and butterfly valve diameter because to make more power, you must burn more fuel and therefore need more air. TO get good mixture of the fuel and achieve good torque at high RPM's, you need lots of air velocity. The bigger the valve, the lower the velocity with the same air volume. But if the valve is too small, it will restrict the airflow.

Everything has to be balanced. Oversizing the butterfly valve will not increase power, and will result in sloppy throttle response and jerkyness at part throttle and poor low RPM performance. Undersizing will cut peak power, but can in some cases improve throttle response at lower RPM's and improve low RPM torque.

If you need more info, get a book on the design theory of internal combustion engines.

 

moto said it best. there's no way to miraculously adjust the butterfly valve for more HP. get a bigger TB, do some head work, or spray.