Originally Posted by
Maximo
I have done a fair bit of dyno testing with the tungsten slugs...they definitely make a noticeable improvement on the engines ability to carry power in the upper end....Quite a few engines start shaking in the upper RPM which absolutely kills its ability to make power in the upper end..adding the Tungsten seems to reduce the vibrations in the upper RPM's which allows the engine to retain power better and spin to a higher RPM...
Using a heavier flywheel will have the same effect. By adding the tungsten inserts you are not magically improving crank balance but merely increasing the rotating weight and the damping effect.
I see these tungsten inserts as the current "must have", no doubt the fad will pass.