1947 Chevy With Rochester B Carb Stalls As Throttle Is Opened

[Guest 4MUL8R]

I cleaned the carb recently and replaced needle and gaskets. I set the float level. Passages seem clean. Power valve moves freely. Idle mixture adjustment screw does modulate idle speed. But as throttle is opened at a normal rate the engine nearly dies. If you quickly open the throttle you can move past this sagging and the engine runs up to a higher rpm just fine. Could you all give me a few tips on diagnosis and repair?

[misterc9]

Check the accelerator pump . Look down the throat . As you open the throttle you should see a small stream of gas shoot down the throat. If not check the linkage it may be dis connected or out of adjustment. Or you may have to take the top off and look further. A way out of adjustment power valve might do this too.

[Guest 4MUL8R]

Thanks for tips. I found a manual online and see what you are talking about. I believe I have a "BC" on this Fleetmaster that is not original. I will check the power valve and the accelerator pump.

[Guest 4MUL8R]

I have checked the carb over again. I looked for the stream of gas in the throat while carb was installed, and saw none. I took the carb off, disassembled partially, and checked the pump. A big squirt of gas came out of the pump outlet hole. I then checked the bridge (?) that holds the power valve check ball, and verified all its passageways were clear. I ensured that the ball at the power valve could move, and would be sprung out of the passage when the valve was sucked downward. I made sure that the tube over the throat was able to pass fuel mist. I put it all back together and tried again. Same symptoms. I sense that the accelerator pump is working as I need to depress the accelerator pedal a few times to get fuel into the intake to start. Wonder what else it could be?

[Dave Henderson]

My father had the same trouble on a '50 Chevy from the time it was new and it never was cured. A flat spot between the idle mixture and that for higher speed. He just cussed the dealer and Rochester and kept on driving. In my opinion they were lousy carburetors. The '47 Chevy should have a Carter W1 carburetor. Perhaps your Chevy has a later engine.

Edited January 6, 2014 by Dave Henderson (see edit history)

[Guest olescarb]

If the wrong bowl to top gasket is used on some of the early Rochester 1bbl carbs the pump will not work so if the pump works with the top off but when it is assembled you can not see it squirt you may have the wrong top gasket or the pump nozzle may be plugged with a piece of debris.

I hope this helps Henry @ oles carb