Sluggish B Carburetor

[JRN1967]

I just installed a B cam and B intake in a 1500 mile model a engine.

I have an A carb that runs excellent, GAV is left at 1/4 turn and forget about it. Never stalls and starts right up cold without any choke or gas needed.

I also have a B carb that gives a noticeable power boost. I harvested this carb off a double B. Last year I threw a carb kit at it, and it ran good enough on my yard jalopy.

Now that I have the bigger cam and intake, I want this B carb on my driver. It starts a little hard, I have to give it a little gas to get it going. I can close off the GAV and it will stay running, but it's sluggish. If I open up the GAV two turns it becomes much more responsive, but the idle comes up with it as well.

Yesterday I disassembled it completely and cleaned all the jets and air passages. Even the passage in the throat I reinstalled the plug with the vertical slit facing in. The cleaning improved the way it starts but nothing else.

Why is it sluggish with the GAV closed? Why does it improve when I open it up two turns?

Thanks, John