Which Ati balancer diameter.
 

I have a 7" Ati balancer.When i talked with Ati they recommended their 8" balancer.It is going on a 620c.i chevy used to drag.My question is will the 7" balancer be fine.

Since no one else jumped in I'll take time. In most cases the larger the damper the better the dampening. Your 7" will be just fine. And in my opinion you've chosen the best. Nothing on my stuff except SuperDamper. Good luck

The 7" will work but I would take the advice ATI gave you,as the stroke and power increase the need for more weight on the end of the crank increases to dampen the torsional vibrations from the firing pulses.your crank life wont be as long with the lighter damper.Bill

ATI Damper
 

Bill hit it on the head. A big three ring would be best but, you could us the one you have.