i got a hit on an internal balanced aluminum flywheel and was thinking about buying it. What do i need ?? internal and external balance and how do i know??when is it necessary for internal and for external?
You need to ask your engine builder how he is balancing the rotating assembly, internal or external, that will tell you what you need to buy.
Personally I would pay the extra to have it internal balanced, that way when you have to replace anything that's bolted to the engine like the flywheel or the balancer you can just buy neutral balance parts , confirm they are neutral and replace .