Swapping flexplates on 302 with C4

As an example, If it is a factory balanced flexplate of say 28 oz imbalance then you could use any other 28 oz imbalance. BUT if a machine shop balanced that whole rotating assembly together including the flex plate then he is right to a point. If they did balance the whole assembly then it would depend on how much material they had to add or remove on the flex plate to get it to balance.

tos is right. the factory doesnt balance every rotating assembly individually, they dont have the time to do that. so they get it close, and weight adjustments are done on the crank. so any 28oz balance factor flexplate that matches the bell housing will do. so find a 164 tooth flexplate that use the same balance factor as your engine does and you are good to go.

as for a machine shop balancing the rotating assembly, once again they change the weight on the crank, not the balancer or flexplate/flywheel. the reason there is so that if you have to replace either of those items, you dont have to rebalance the engine rotating assembly as long as you again use the proper balance factor for your engine.