Stovebolt.com Forums The Shop Area The Engine Shop Straightening the Rochester B and BC castings

what are the most likely sources of the leak(s)

Needle & seat not sealing
Dirt in the float bowl
Float level too high

I have seen at least 3 different thickness of gaskets used on these. What is the proper thickness? And if the carburetor had a thick gasket, and the kit has a thinner one, I suppose that could affect the power valve some, since with a thicker gasket the valve or ball is moved farther away from the power piston, and vice versa.

The float bowl to air horn gasket was 1/32" thick originally. The cheap rebuild kits will very likely include a washer in 1/16" thickness or almost that and I have seen some rebuild kits with gaskets about 1/64" thick (very thin). Some people think it is suitable to use 2 gaskets...but please don't include me in that crowd. In my opinion 1/32" gaskets with straight castings offers the only hope you have of making this poor carburetor work as it was designed. Any vacuum leak will affect the power valve. Using two gaskets will worsen the warping of the air horn. Using two gaskets without buggering one up to account for the extra thickness under the jet mast will change things (not in a good way). 1/16" thick gasket will make warping worse. Jon H (CarbKing) and I discussed the possibility of using a compressible gasket (like modified pvc---the type used for shower pan liners or silicone rubber, etc)...we really did that and in serious terms. The problem there is cost plus time and the need for one that will resist ethanol laced gasoline plus be compressible enough to actually help. We decided it was like putting a band-aid on a leg amputation. Lots of variables plus you STILL have that wonky power circuit to consider...which at this point in time represents a real challenge. Possibly the best answer would be to bore and re-sleeve that piston sleeve in brass. But even that would fail in the presence of ethanol-laced gasoline. In the study of all the Rochester B and BC models I discovered 3 different strengths of power piston springs. This is from looking at 5 carburetors plus some misc parts I had saved from the mid 1960s. Which is correct? Who knows? For me it simply became a question with no answer at all. As I recall Jon H said there may have been 7 or 8 different strengths. A stronger spring will keep your power valve open much longer and a weaker spring will close it sooner. Go and try to find any Rochester data on this...I could find only scant data and I spent months trying.

Good luck with these. The challenges are plentiful.

I don't think the bore for the piston is too bad, and having 7" HG holding it in the bore is pretty good isn't it? I got the kits from Mikes carburetors. The impressions on the gasket looked like good contact. I'd still like good input on the static fuel level as that is more important than float level and is why some carburetors can have the fuel level adjusted, on the fly.