The Stovebolt Site Forums The Shop Area Engine Shop Leaky Rochester

This is all new to me.

Why is my carb leaking here?
The float is set at 1 9/16 closed and 1 3/4 droop.

Hard to tell exactly in that picture, but the bases are known to warp on those Rochester's. Would a double gasket with RTV help?

Its dripping off of the linkage

There is a story on here recently about how to cure curved pot metal carbs.

Ed

Unless the inner walls are warped. I’m not seeing how it relates to fuel running out of the linkage

Actually there are probably hundreds of posts about this...Rochester B and BC carburetors are very hard to keep from leaking. There are a couple of reasons why, but please do not use 2 gaskets. That will only make the situation worse. Here is a link on how to straighten the castings: https://tinyurl.com/y8bbrhw6

Since we don't know what year or model of truck you have it is hard to suggest a better solution. A Carter carburetor (instead of a Rochester) would stop the leaking and dribbling and would give you other advantages. Please always tell us the year of your truck, the year and size of the engine, etc. It is easier to answer your question if we know. Typically the Rochester B and BC float settings are 1 9/32 level and a float drop of 1 3/4, so one of your settings seems correct. New needle/seat? Different fuel pump (an electric which is too strong, maybe?)?

With the Rochester B and BC, fuel can be coming from a few different places and running down to where it drips off the linkage. If your top (air horn) and float bowl are warped, the gasket will not seal. When this happens you can lose vacuum inside the carburetor (will disable your power circuit), and you can have a situation where the fuel sloshes up when you turn a corner or go up/down a hill to the point where it just runs out the seam. The air horn is only connected to the float bowl by 4 screws and over time heating/cooling causes warpage. GM knew this and why they never solved the problem is not known, but they didn't. If your float/needle/seat are not working correctly that will also cause leakage...especially if your castings are warped. And if you have a pump with too much pressure, this will cause the needle and seat to work incorrectly or fail and this will cause leakage.

And one other possibility is a ruined float. Take it out and shake it. If you hear anything inside, it isn't going to work as a float. This will cause bigtime leaking.

According to this chart
http://www.chicagocarburetor.com/pdf/Instructions-Rochester-B-BC-BV.pdf

All the Chev B’s, BC’s and BV’s used the same float settings. Mine appears to be 1/4” too high. It’s a place to start.

Jon,
The carb was recently rebuilt so it has all new internals. The floats are empty and dry

Thanks...to set your float level turn the air horn upside down and set on a flat surface (gasket in place). Then measure from the gasket to the top of the float. That should be 1 9/32". To measure the drop, leave the gasket in place and turn the air horn right side up. Let the float hang free and measure from the gasket to the lowest part of the float (would have been the top of the float with the air horn upside down). This ought to be 1 3/4". Good luck.

Oh, one other thing...you have two floats connected to a central pivot. Make certain your floats are (a) parallel and (b) not rubbing on the side of the float bowl. If they're rubbing on the float bowl (which I've seen happen) it will cause this kind of problem.

Rubbing the bowl?
How do you prevent this with all the slop in there?

Hang on...wouldn’t a float height of 9/32’s give me more fuel in the bowl than 9/16?

Yes, it will put more fuel in the bowl than 1 9/16". But first we have to figure out if your float/needle/seat are working in concert to stop fuel flow when they should. If the float (either of them) rub against the sides (walls, if you prefer) of the float bowl it will cause the float to drag. If this happens, you'll get too much fuel in the bowl. It is just like a toilet bowl, actually. If the float is bent and rubbing on the tank you'll overflow it.

Assuming it drips after you shut off the engine, check this link:

Throttle shaft leak

Jon.

Follow up after taking the carb apart for the 19th time.........

Contrary to popular assumptions. This dripping off of the accelerator pump linkage was NOT due to warped carb bodies. But rather a piece of schmootz migrated past the inline filter and settled on the needle tip. Holding the needle open enough to over fill the float bowl and run gas out of the linkage port. I saw a fuel stain (E10) on the linkage about 1/4” above the casting.

The dreaded schmootz. Good find.