dumb question, but i figure ill ask anyway, you did have the machine shop balance all the weights on pistion/wrist pin/rod combinations right? i have seen people in the past that have skipped this step or theyre machine shop didnt get the tolerances close enough and it still threw the motor out of balance. we have 3 trucks turning 5 at the line and at least 42-4500 down the track with with one turning 5-5500rpms and they all have stock components and havent had any trouble granted one of those has arias pistons and hardended rods (which has nothign to do with balance). i would try to find out from the machine shop how far out it was at 6500 before spending a small fourtune in a crank. also wouldnt be a bad idea to check into how far out the rods were, i know our machine shop keeps track of all that in theyre system that we can call back and get record of it down the road if we need to. most of the time the crank is already pretty close, its the rest of the rotating assembly that is generally most out of balance.
