Originally Posted by Red Bread
False. Only a flat six and a straight six have primary balance for six bangers. You're also wrong about the V10, which is not inherently balanced. But a 60 degree V12 or a flat 12 are.
Yes, I was wrong using the term inherently balanced. I was actually referring to a need for balancing shaft and the angles I listed do not need them to make the engines smooth. However, you are right regarding inline and flat 6 they are in fact completely balanced.
As far as the V12 any angle is balanced since we have each bank as a inline 6 which is balanced on its own. Therefore making any angle in the V12 just as balanced.