307 & 350 Olds Internal or External balanced?

[tmaj1865]

I swapped a 350 olds for my 307 in my 87 442. Now I have a small vibration when I rev the engine. I think I used the 307 flywheel on the 350.
Is there a difference?
Thanks

 

[85t5mcss]

Both external balance. Shouldn't be a prob. Double check, make sure all fasteners are tight, too.

 

[joe_padavano]

Both external balance. Shouldn't be a prob. Double check, make sure all fasteners are tight, too.

All 1968-1990 Olds V8s use the same flexplate (big and small block) so that's not the source of your vibration.