60° v6 is perfectly balanced. A sixth of a crank rotation for each piston stroke 
In it's true self contradictory way wiki says-
A V-angle of 60 degrees is the optimal configuration for V6 engines regarding engine balance.[3] When individual crank pins are used for each cylinder (i.e. using a six-throw crankshaft), an even firing interval of 120 degrees can be used. This firing interval is a multiple of the 60 degree V-angle, therefore the combustion forces can be balanced through use of the appropriate firing order.
The inline-three engine that forms each cylinder bank, however, produces unbalanced rotating and reciprocal forces. These forces remain unbalanced in all V6 engines, often leading to the use of a balance shaft to reduce the vibration.
Also from elsewhere on the web of lies-
And there’s an equation to help determine which configurations will work best. In a four-stroke engine, an individual piston fires every 720 degrees (two crankshaft rotations). If you divide that by the number of cylinders, you get a figure that represents the optimal degrees of crankshaft rotation between cylinder firings.
For example, a four-cylinder would like to fire at every 180 degrees of crankshaft rotation (720/4=180). Having firing events that occur in equal increments, as in this instance, is best for balance. The flat-four fires at 180-degree intervals, and its V angle is 180 degrees, which leads to a balance of firing forces. The flat-four, in fact, balances all three of the different types of forces.
A cross-plane, 90-degree V-8 has balanced rotational and reciprocating forces because it is a lot like four of the balanced 90-degree V-2s shown in the aforementioned illustration. To balance the firing force, a cylinder has to fire every time the crankshaft rotates 90 degrees. Since the bank angle is 90 degrees and the firing forces occur in 90-degree intervals, the cross-plane V-8 also manages to balance all three of the forces.
A 60-degree V-6 engine isn’t quite as successful. The rotational and reciprocating forces can’t be completely balanced because this type of V-6 is essentially two three-cylinder engines stuck together. Inline-three engines, because of their odd number of cylinders, are inherently imbalanced and will tend to rock from end to end. A flat-six engine manages to cancel the rocking because the opposing banks exactly cancel out each other’s motions. Putting two inline-threes together, end to end, to form an inline-six also works because each three-cylinder end of the engine exactly cancels the forces of the other. And since it’s basically two straight sixes joined at a common crank, the V-12 is naturally balanced regardless of its V angle.
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Topic: Thinking about the Kit Car (V6 - inspired by Wheeler's Workshop) (Read 2820 times)