capstan with adjustable pulley

There are 2 main reasons why you should use a Bellcrank to ensure consistent throttle
sync between the left and right banks on a "V" engine instead of using a link across
the engine from one bank to another.

A Bellcrank is placed in the middle of the "V" will distribute throttle movement equally
between the left and right banks of your engine (provided you set the two cross rods
to the same length).

If you use a cross link between the left and right throttle sets instead of a Bellcrank,
you may experience one of both of the following 2 points,  which can be very difficult to
diagnose if you are not looking out for them.

1) As your throttles begin to open, you need to have the same type of airflow and air
turbulence on every cylinder in relation to the intake valve(s) and injector placement.

If you use a cross linkage instead of a Bellcrank, one bank of butterflies is going
to open in one direction, and the other bank is going to open in the opposite
direction, in relation to the injectors and intake valve(s).

This can create a difference in fueling between the 2 banks, especially at low throttle
openings during idle and cruise.

2) The second point is that, as the engine warms up, it will usually expand.  This can
cause the cross link to "pull" on the second throttle set.  This will likely cause the second
throttle set to be slightly more open than the first throttle set, causing your engine to
run more roughly at idle.

A Bellcrank automatically compensates this movement by allowing the linkages to
equally open up and rotate the Bellcrank mechanism.

The bottom line is that if you are running a "V" engine and have a set of throttles on
the left and right banks you must use a Bellcrank.