bentman

I put a internally balanced 408 in my 73RR & had to buy a new T/C because it had weights on it. Do I need to buy a new flex plate?

MercuryDon

No on the flex plate. If the engine was not balanced with the damper on and it was a exterally ballanced damper you will need to replace it also.

bentman

I'm confused some people say I need a new flexplate & some say I don't.
B&M says I need 1

1966sportfury

if it is internally balanced, you do not need a weighted flex plate or converter, if its externally balanced you will need a weighted flex plate or converter. if you put a weighted converter on a internally balanced engine, you will need to replace the bearings after start up., and probably a new tranny.

Silverick

The old flex plate should be fine. The weights are on the converter. You probably could have taken the weights off of the old converter and been fine.