Just to help out some of the other newbies on the board, I'll review my take on harmonic dampers.

First off, they are not balancers, they're dampers. The exception would be motors like the SBC 400 that used an eccentric balance weight on the hub along with an eccentric weight on the flexplate to balance the motor, rather than internally balancing like most motors.

A harmonic damper is used to help cancel harmonics which are set up in the crankshaft by the force of the piston/rod slightly twisting the crank in the direction of rotation when the force of explosion in the cylinder is applied to the crank. It will only twist just so far, then will spring back opposite the direction of rotation to the limit of the material involved, then spring back the other way, then the other way and so on and so on. If left unchecked, the harmonic vibrations set up in the crank from all this to and fro twisting will destroy the crank in short order, causing it to crack and fail.

That's the job of the damper inertia ring around the outside of the damper. It's mounted in a slightly flexible material (we call it rubber, but I don't think it's rubber. Damper guys call it elastomeric material). The ring moves back and forth circumferentially on this elastomeric material and helps to dampen the crankshaft harmonics.

It looks to me like there are different outside diameters on dampers based on the crankshaft stroke and power output of the motor. 400's had the longest stroke in the SBC lineup and also used the largest damper diameter (8"). The fact that they also had balancing pads is inconsequential to the subject matter being discussed here. Shorter stroke motors such as 283's and 327's had smaller diameter dampers. Some low output 350's had smaller diameter dampers as well. So, it appears to me that the amount of MASS in the damper ring is what makes the difference in damping the oscillations, depending on stroke and engine output.