Hi to all, I have never had a balancer rebuilt - yet. But, the other day, I had a 413 engine at TDC on a stand in my shop, and decided to "test" some balancers I had removed from engines over the years. Result of testing 6 balancers : two were accurate, two were off by ten degrees, one was off by 15 degrees, and one was off by 30 degrees or so. So, it isn't much good using a timing light to tune your engine if the timing mark is off ! Suggest testing your balancers by placing engine at #1 TDC using a piston stop device ( one can easily be made by busting out the porcelain out of an old spark plug and threading a bolt in the center of the remaining metal ) . John