pictured are all basic 5 balancers. there's actually 7 counting late 53 and early 57 (not shown). early 53 used a cast iron crank pulley, not to be confused with the 54/55 cast iron crank pulley of the 264, which came in single groove and rare 2 groove options for cars with power steering. the early 53 crank pulley is easy to identify as it does not have a timing mark on it. compared side by side with the 264 version, you can see they are really different looking.. late 53 looks like the 54 to 56 variations but take note that they have a different counter balance than the 54 to 56 (-59) 322 variations which may or may not have pulleys swedged on them, depending on the year. late 53 also does not have a timing mark on the balancer.
364 balancers all have half the casting counter weight as the 401/425. early 57 used a 3 bolt pulley mounting design like the previous 322, which changed mid year to the late 57 to 61 style which are all interchangable otherwise. unlike the 322 versions, the 57 to 66 balancers can spin on the main yoke, after years of rubber deterioration. depending on how your rebuilt engine was rebalanced, this can throw your engine out of balance. often, machinists don't pay attention and balance bottom end assemblies with spun balancers. to tell if the balancer has been spun, keyway should line up with the timing mark, when looking from the back of the balancer. if you have the balancer installed on the engine, and want to be able to tell, without removal of the balancer. take not of where the timing mark is. follow your eyes, counter clockwise to the left. take note of where the counterweight starts. mark with a felt pen on the outer balancer ring where it starts. now take a flexable tape measure and measure from the timing mark, counter clockwise to that new mark you made where the counter balance starts. on the 401/425, that measurement is 5 inches. on the 57 to 61 364s, that measurement is 7.25 inches. if your balancer is spun, send it to use for a rebuild, we can send you a new on (401/425) or sell you another good used on. take note that from the factory, although the 401 and 425 used the same balancer casting, the 425 had slightly more counterwight to it via less removed material to the casting. the tolerances were so close, however, that later in the 70s, buick sold one balancer replacement part number for both applications. when you get your engine rebuilt, both the flexplate and balancer MUST be balanced with the bottom end. while we are on the subject, you can also tell if your flexplate is on wrong by removing the flexplate cover and looking to see if offset lump on crank mounting flange lines up with counter weighted section of the flexplate. 322/264 flexplates cannot be put on wrong via guide pin.
57 and later balancers MUST be torqued to 220ft pounds!!!!!! extremely common and overlooked problem. these engines are all slip fit, unlike a chevy or most other engines for that matter. the bolt is 100% responsible for keeping the balancer tight and keept it from walking. when is walks, the balancer cracks through the keyway. left unatented, the balancer then destroys the crank snout. the balancer is softer than the crank snout, so it will receive damage first. as a patch job on an unrestored engine, you can put on another good used balancer if this happens with sleeve retainer, despite damage to the snout, but i would NEVER suggest using a damaged crank when performing a rebuild. crank should get tossed. with the chain gear removed from the snout, you can easily tell if the snout is damaged via grooving. whenever purchasing a used balancer, look for the keyway crack. look to see if keyway is hogged out from walking. look to see if balancer as spun... and look for damage to seal journal via pitting from trapped condensation in the rope, or heavy grooving from the dried out seal acting as an abraisive over time. feat not, if you have damage like that, the balancer is still good, it just needs a repair sleeve, that we also sell. when i polish seal journals, i typically start with 120. skip to 400, then 600, then skip to 2k grit.