The Stovebolt Site Forums The Shop Area Engine Shop How do governors really work?

I pulled the carb and governor off my 302 Jimmy today. The carb I understand, its a Holley AA1 which is identical to the flathead Ford Holley 94 except for the venturi size. The governor is a King-Seeley Varispeed unit with a throttle butterfly with a spring and a piston. There is a screw that you can adjust the tension on the throttle butterfly spring, and a vacuum port that goes somewhere into the bowels of the unit. The throttle shaft is offset on the butterflies.

How does the governor actually work? Does it sense manifold vacuum? There is no connection for external hoses, linkages, or anything.

I'll probably not put it back on the engine, but I am curious.

4onthefloor,

We use the style of governor you describe in some of our gas and LP forklifts. This style is known as a 'velocity governor' and is varied not by vacuum, but by the velocity of the air the engine is pulling through it. There is a large surface area diaphragm that reacts to the velocity of the air through the venturi and opens or closes the butterfly in the throat.

Stuart

what atomarc said , that is how our yales are equipted , keeps the kids from over-revin the engine liftin stuff , they think WIDE OPEN makes it lift faster ..it doesnt but ya cant tell a 20 yr old that ...they think they know better .

The air velocity governor works as previously posted, and is one of the two most common types of governor.

The other common type operates from oil pressure.

A third type used on older pumper fire trucks operated from water pressure.

Jon.

never seen one on oil or water just the one,s stated and mecanical...doc

Doc - I don't remember Chevrolet using either the oil or water; this was simply a comment on governors in general. The water units I have seen were monster units with huge springs, used on some pumper trucks of the 1920's.

Jon.

I think there are two different type of governors being referenced here.
The one 4onthefloor has is a speed limiting governor to limit maximun rpm and the type I would expect to be on a pumper would be one to maintain a constant speed under varring load as would be found on a welder, generator, tractor or other engine where the throttle would be set at a fixed position and the governor would maintain a given rpm under varying loads.

The "water" governors on Pumper trucks are a safety feature designed to protect the firemen from overly high hose pressures. Say a fire engine is pumping through two hose lines at 100 psi each. Then one of the men on one of the nozzles shuts his line down. Suddenly all the pressure developed by the fire pump is exerted on the one remaining hose, with a correspondingly higher nozzle reaction force - quite dangerous.

The governor used reacts according to the pump pressure exerted on the water from the pump. In other words, there's a water line from the fire pump to the governor, and, (if the governor is "enabled") when the pressure spikes in the pump, the governor closes the throttle correspondingly, to lower the fire pump pressure. It sounds like the same principal as a vacuum operated governor, only with water pressure. Used broadly on fire engines from the 30s on.

Not that anyone asked . . . ;-)

-Michael

And I thought this wa going to be a political post. :p