The Stovebolt Site Forums The Shop Area Engine Shop 1951 Chevrolet Rochester Carb leak

I had my carb rebuilt on my 1951 Chevy 3800 panel with a 216 motor. When I start the truck it starts and runs great but after it warms up and is idling the carb leaks lots. Ideas of problem? All screws, bolts and connections are tight. Seems to be coming from the firewall side, middle of the carb? (you can tell I am not an experienced re builder - just looking to learn) Thanks for your time.

Check your float setting first and gasket. Make sure the inlet needle is seating properly. If leak still persists, it most likely a warped casting. Take the carb off the manifold and disassemble the air horn and gasket where it mates to the carb body; Put the air horn back on the carb body and hold it up to a light. If you can see light coming through you have a warped casting. You might be able to get away with a little bit, but I would look for another carb. There is a temp fix that involves disassembling the carb completely, and making a jig to clamp the air horn and body and bake it in the oven. Someone will chime in on that.

Tough to know for sure based on your description, but a couple possibilities:

1) Float height not correct or float sinking. Don't remember the spec off the top of my head but the Rochester was my first rebuild, knowing less than nothing, and it was easy to do. Have a shop manual that can help you through it?

Float buoyancy can be checked by submerging it in very hot water and looking for bubbles.

2) Carb castings warped to the point you're seeping fuel. Possibly in combination with one of the conditions in #1. The fact that it runs OK might suggest the warping is relatively minor.

There are a few other possibilities as well, but these give you a place to start. There are some very easy to understand rebuild videos on YouTube and if you buy a kit from a reputable source....the rebuild could not be any easier.

Fiddling with the float height cured my leak. But your may or may not be so simple. The B has issues. Many will suggest you replace it with a Carter but might as well try some simple things first.

Thanks for the info. I tried unhooking my gas line and stopping it up. Then started the engine to run the gas out of the carb. I then re-hooked the gas line and fired it up. So far no leaks. Hope that has it. Thank you very much. I am a slow learner but hungry to learn.

You did the right thing there. If there was a piece of dirt in the needle & seat, that will flush it on through. You just learned a good trick I have been doing for years. You can just pinch the flex fuel with vise grips or equivelant instead of unhooking the line.

George (Wrenchbender Ret),
Does plugging or removing the fuel line, allow the extra air to suck in any debris?

No. Blocking the flow of gas & running the engine till it uses up all the fuel in the bowl causes the float to drop all the way down & the needle valve to open all the way. The in rush of gas washes the foreign mater off the needle & seat.

Thanks for that George!