Im running a 250 with the 407N factory lighter crank with a 6 3/4 sbc damper (summit brand) and it revs real great now. No real vibrations at all up to the rev limiter at 6400. And it gets there alot faster than it used to with the stock balancer. Plus another added bonus is the flywheel stopped comming loose. I also have a 153 tooth flywheel from a vette that weights 15 pounds and a muncie in the car. The whole lighter rotating assembly seemed to do wonders for the reving of the engine.
