vibration in new motor trans combo
 

I have a new prof built balanced short block 306 that i put a c4 behind i did install the c4 balanced flywheel on the combo. Don't recall the balance but its the one e everyone said to use. Now on a hard acceleration i have a mid rpm vibration.
I did use the original 5.0 balancer. Could this be my problem and if it is a potential issue what could i try prior to riping into the rotating assembly?

Re: vibration in new motor trans combo
 

Did they use your original block and crank?