What is the difference between external and internal balance? Which one will be better?

I plan on ordering eagle compitition rotating assembly part #ESP-B12508030 from summit for my small block 400, but the assembly is internal balanced and chevy 400 engines are external. I can order a external balance assmbly but I would like to know which would is better external or internal balance but the part number I listed is the one I want.|||all stock small blocks but the 400cid is internal balanced, and the 400 and all stock big blocks are external balanced.





internal balanced means that the rotating assembly is balanced on the crank, external balanced means the that balancing is done on the harmonic balancer and the fly wheel.





but just cause the 400 comes externally balanced dont mean you cant change it, and if your buying an internally balanced rotating assembly then you need the right fly wheel and harmonic balancer.





hope that helps you under stand how it work|||400 small blocks, and 454 big blocks, are both externally balanced. The biggest things that they only require is a balanced harmonic balancer, and a balanced flywheel, or flexplate.





As far as trying to change from one to another, I would just go with the external balanced parts.





I had a 400 small block in my '79 Monte Carlo, bracket racer, but opted it out for a 305, to try to make it a NHRA stock eliminator car. I still have the 400.|||externally,|||Wow what a selection of answers! Internally balanced is more than a balanced crank. It means that the pisotns were weighed and the heaviest were ground down a bit so the were all fairly equal in weight. Same goes for the rods. In other words, moving internal parts are balanced. The harmonic balancer has its own function.