Be careful when removing the power piston. The stem can break off easily and these are not longer being produced. Push down on the stem and spring with your finger, then let it snap back. Do this over and over until the piston comes out. A frozen stem is another problem all together. Try spraying silicon spray lubricant into the vent hole. Hot Idle Compensator
The conventional vacuum sensitive power piston and power valve are used for light duty power requirements. When manifold vacuum drops to a pre-determined point (called power cut-in), the power piston is moved downward by spring tension to force the power valve plunger off its seat to provide the correct fuel enrichment for light duty power requirements.
During moderate to heavy engine loads when additional fuel is needed for extra power, a second power valve is used. This valve, located at the bottom of the accelerating pump well, is mechanically actuated by the accelerator pump plunger.
As the throttle valves are opened to a pre-determined angle, the accelerator pump plunger moves downward in the pump well, and contacts the power valve plunger, opening the power valve.
Fuel flows past the open valve through a passage in the float bowl on into channels leading to the power restrictions to supplement fuel delivery from the vacuum operated power valve. When the mechanical power valve is opened by the accelerator pump plunger, a vacuum signal from the main discharge nozzles is transmitted to the power system and open power valve. The aluminum check ball in the bottom of the pump well responds to the vacuum signal change and is lifted off the seat to supply additional fuel to the pump well for power requirements.
The combination vacuum and mechanical power systems are specifically calibrated for correct air/fuel mixtures required by the engine appliation. No special adjustments are required in the field. However, the pump rod adjustment should be checked and set to specifications during normal servicing of the carburetor to ensure correct fuel flow from the mechanical power valve system.
The mechanically operated power valve, at the bottom of the pump well, is removable for normal service cleaning and replacement as needed.
Be sure the piston rod isn't bent. It needs to press straight down on the power valve.
Be careful when removing the power piston. The stem can break off easily. Push down on the stem and spring with your finger, then let it snap back. Do this over and over until the piston comes out. A frozen stem is another problem all together. Try spraying silicon spray lubricant into the vent hole.
Q: Upon cleaning my carburetor I noticed this little hole that flows from the bowl through the power valve when it is closed and open. Am I missing a check ball here or something? It seems fuel will always flow through here whether my power valve is open or close. I started cleaning and inspecting my carburetor because I have an off idle bog . It runs good at high rpm and I can rev it up . It also idles good . But if I floor it off idle it will die .
Replacement power pistons are avialable for some Rochester 2g carburetors. You need to compare the dimensions provided to be sure you're ordering the correct one. Some 2G carbs use a different power piston that is not available.
The power valve sits on the bottom of the 2 Jet carburetor, between the 2 main jets.
This is for the early 2 Jet carburetors. Part #56-2. 5/16" threaded end.
Even though they look the same, this power valve does not work on the marine 2 jet carburetors, thought we have had customers modify the power valve to work.
There are 3 other power valves to consider.
This power valve is for the later Rochester 2 Jet carburetors. Part 56-41. 3/8" threaded end.
This power valve is also for the later 2 Jet carburetors. Part 56-40 . 3/8" threaded end, with the cone head.