Anyone have any information on the governor use on a 1974 F600 330 truck engine? The number on the governor cover is D2Tf-12450-AA. It mounts under the carb and is a butterfly design that closes when the engine over speeds. I can not determine the signal source that closes the butterfly. Have no idea if it works or not as I have never heard the truck run. Any governor I have ever been around has a way to determine speed, this one is marked 2800-4000 rpm nl. How it determines that speed I do not understand as there are no signal lines from anything. Just got done rebuilding the carb and while things were apart just thought I would look at the governor. Thanks for any information. Dennis

 

The signal comes from the distributor, there should be a line running from the governor to the distributor.

 

Ford used three different style governors on their truck engines, velocity, vacuum and mechanical. It sounds like you have a velocity governor, that's probably the most common one.
Here's what Ford's shop manual says about the velocity governor:
"The velocity governor is a single unit mounted between the carburetor and intake manifold. There is no provision for repair of this governor. It should be replaced when damaged.
The governor is operated by a combination of manifold vacuum and air flow past the governor valves. The governor throttle valves are offset in throttle bores so that the combined force of the manifold vacuum and the fuel/airflow through the bores has a greater effect on the larger, upstream area of the valves. This forces the throttle valves to move toward the closed position restricting the fuel/air flow. The closing action of the throttle valves is opposed by the control spring. The control spring is attached to the throttle shaft cam. The cam provides a balance between the closing action of the throttle valves and the action of the control spring at all engine speeds.
Under operating conditions, the governor throttle valves do not close, but remain open enough to allow the required quantity of fuel-air mixture to flow into the intake manifold to maintain the governed engine speed.
To maintain the proper vacuum to the distributor, the governor has two interconnected vacuum transfer ports and a vacuum transfer plunger. When the governor throttle valves are forced towards the closed position, vacuum from the lower port is supplied to the distributor to maintain sufficient spark advance. When the governor throttle valves are open wide enough, the plunger shuts off the bottom port and the top port supplies vacuum to the carburetor distributor vacuum passage for sufficient vacuum to the distributor."
It then goes on to give the speed adjustment procedure.
So, bottom line is, air flow velocity through the carb is the signal for the governor.