Rochester 2 Jet, 2G, 2GC, 2GV Power Circuit

The Rochester 2 Jet power circuit includes the power piston assembly. At idle the piston is pulled up (vacuum) off of the power valve making the power valve close. As rpm is picked up vacuum drops and the piston starts to drop. Eventually it pushes the power valve open allowing extra gas to enter the system.


2 Jet Power PistonBe sure the piston rod isn't bent. It needs to press straight down on the power valve.
2 Jet Power Piston
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.

2 Jet Power Piston
The power piston presses down on the pin sticking out at the top, allowing extra gas to flow.
2 Jet Power Valve
The power valve sits on the bottom of the 2 Jet carburetor, between the 2 main jets.
The illustration on the left is for the early 2 Jet carburetors. Part #56-2. 5/16" threaded end.

This does not work on the marine 2 jet carburetor.

There are 3 other power valves to consider.
2 Jet Power ValveThis power valve is for the later Rochester 2 Jet carburetors. Part 56-41. 3/8" threaded end.
2 Jet Power ValveThis power valve is also for the later 2 Jet carburetors. Part 56-40 . 3/8" threaded end, with the cone head.
Mercarb Power ValveThis is the power valve for the Mercarb, 2 BBL marine carburetor. 56-22
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