i don't believe balancing is an exact science and it may depend on how "exact" the user wants to be. for me i've gathered up 2 or 3 sets of rods and picked 8 "good ones" out of the bunch. i think the factory service manual states plus or minus 4grams for rod weight but doesn't specify which end so i just took that as a total weight. i think the service manual does give specific small end/big end weights for hemi's. if you have several sets just try and match them up.