The Stovebolt Site Forums The Shop Area Engine Shop 235 Rochester B carburetor

Ok so I'm having some flooding issues with my Rochester B carburetor on my 1954 3600 chevy truck. I've checked the float measurements and they seem correct. I have a float drop of 1-3/4" and when you flip the top of the carburetor over the other way, it's 1-9/32". But I noticed something today I haven't noticed before. There is this little pipe or nub that sticks out from the top half of the carburetor and mates with a small hole in the bottom half of the carburetor. Well half of that pipe is missing and I'm now wondering what it does and if it's my issue. I have a picture but I'm not sure how to load it on here, so maybe someone could tell me how to do that lol.

Float level could be correct, but, if the float has fuel in it, the level will not matter. Pull the float off and see if you hear fuel sloshing around or it feels heavy.

Did you do anything lately to fuel system? Did you put on a new Fuel pump? Check what Joe said.
You need to describe exactly what is happening and when. "Flooding issues" is not descriptive. Leaking?-Where? Stalling?-When? Won't start? Popping at carb? Need good info. In other words, what makes you say it is flooding?

Ok so this is what I've done so far. I've replaced the coil,condenser, point's, plugs, wires,cap,rotor,fuel pump and rebuilt the carburetor. I've taken every fuel line off that the truck has and sprayed cleaner down them and then blew them out with air. The timing is dead on and it has a 35 degree angle dwell. The float is new and isn't taking on any fuel. I have adjusted the float drop at 1-3/4" and when you flip it the other way, the floats are at 1-9/32". It doesn't seem to be hanging up either. It seems like it will sit and idle forever with no problems, but after driving a few miles it starts dying. When it dies the first time, it has to sit for a few minutes before it will start. Every time it dies after that it fired right back up and goes for a little while before it dies again. After it dies once I check under the hood and there has been gas leaking on the front of the carburetor where the two half are bolted together. Also at times there as been gas on the throttle plate rod. Both of those thing could be normal though from what I've read, but it also makes me wonder if it's getting to much fuel. So frustrating lol.

1. It will leak at gasket and shaft if getting too much gas...or as explained in no. 5.
2. If you installed the wrong fuel pump the pressure could be too high, especially if you installed an electric.
3. The floats must be check by seeing if they float in water. Then held under for bubbles. Shaking not conclusive.
4. Clean needle valve passages.
5. The carb bodies are many times warped and they leak. Do not fix with extra gaskets. Must be de-warped.
6. You may have left off the seal for the needle valve seat.
7. You did not continue on your other post after you found several problems and you started this new post. This is not the way to get help. You need only one post per problem.
8. Do not decide what is wrong before you ask for help. It misleads us when you say flooding. Your other posts says it dies on you. You said you found points set too thin and then it ran for a long distance, then you found cracked cap, fuel pump had a stripped screw. You said it starts right up right after dying. That is not flooded. Sometimes your descriptions are of a motor not getting enough fuel. Throw the carb and the pump away and buy new and then report. You don't want more than a 4 PSI pump!!!! You have rebuilt the carb and taken it apart several times. Don't take anything else apart, you may be creating several problems and chasing your tail.
9. As I tried on the other post, you still did not say that after dying, you took off air cleaner and observed if gas will squirt out of holes in carb throat when you give it throttle.
10. Did you say in other post that you disconnected the line at carb inlet, cranked motor and filled a jar real fast? I think you did say that...yes?
11. Did you say that you have check spark at a spark plug lately?
12. It is NOT necessary to start taking things apart UNTIL you have tested these things at the moment it won't start, as I explained in your other post(s).

Sorry for starting a new post I wasn't thinking, it's probably just the frustration. The fuel pump is the correct for the year of the truck, 1954 and it's not a cheap China made piece of crap either. It's a mechanical fuel pump that looks exactly like the original. The truck did run fine for almost 20 miles, that's why I thought I had it figured out. Then it started dying again, It's still doing the same thing. So I decided to do a complete tune up which didn't fix my issue apparently. I'm really close to buying a whole new carburetor, like you said. The seal for the needle valve seat is there, I rechecked that yesterday. I can check the float by placing it in water, it's the only thing I really haven't done. What are the chances of a new one taking on fuel though? I thought originally it was a ignition problem, at this point I really have no clue.

It may be the gas cap is not vented. After running awhile, remove the gas cap & listen for a suction noise. Try running with the cap loose & see if it still dies after running a ways.

I did that too and it still dies.

The possibility exists that one or more of your "New" ignition components is failing when it gets warm. The most common one would be the condenser. Although the coil can exhibit the same symptoms. Try your very best to stay away from Chinese made ign parts. Good luck.🛠

I have also wondered if the foreign made coil and condenser could be bad "new" parts.

I have made a huge effort to search for points that are American made. Points that are reliable right out of the box. There are none except ebay NOS made by Delco Remy. Not Delco. Not Napa. New USA made points for older trucks do not exist anymore. The actual maker is well hidden even with the Federal rules on Country of Origin and per cent of USA content.
No I don't expect a new float, if copper/brass, to sink. I agree. You say it's not hanging up on the sides of the bowl. But the tests I have mentioned will tell if it's fuel or spark. If it's timed and has fuel squirting and spark, it will fire.........100% sure.
Your task is to catch it when it won't fire. You can't catch the problem if it is starting OK. Gotta be ready to observe spark/gas or you will never find it unless you buy the correct parts. That may be the next part you buy or $500 from now.

Yeah I know, I've already thrown $250-$300 of parts at it. I still say it was time though. Like I mentioned earlier I did find a set of worn out points and a cracked distributor cap. I'm going to let a old timer I know locally take a look at it at his shop. The old guy has been working on cars for over 40 years and he's good on this old stuff. I'm going on vacation and I need a brake from it lol. I know it's something you guys have probably mentioned and I'm sure I've over looked something. As soon as it's figured out, I'll be sure to inform you.

Guess my other post didn't go through, where I said that these posts are only helpful if people come back and explain what it was that was wrong, but now I've added "Or, I might just be looking at the wrong date, and that was an almost brand new post, but it's rather confusing since the date stamp on the last post says 8/20/17 yet today is only the 19th, so he must have posted it tomorrow. LOL."

Just 40 years?...............a novice then aye?

To some I suppose lol.

Leonard, your other post didn't come through, because it had not yet been approved. New members are in moderation until they've had four posts approved. Since you posted this, I deleted it rather than approving it, to avoid duplication. Now that you're out of moderation, your posts will show up immediately upon submission.

So apparently it's the one thing I didn't think of, the ignition switch.

Thanks to Joe H,
Flooding problem solved once I removed float and heard a small amount of gas sloshing around inside and replaced float. Thank you, Joe.
Chuck 52

Look in the electric bay section---up top as a sticky post. There are two posts, actually. You'll see I've done a great deal of work on the condenser...which is your ignition weak link, by the way. Big time weak link. Buying one of the Chinese condensers is like setting fire to your money. They're all made in one "factory" (could be some guy's garage) and there is about as much precision in them as there is in a handful of gravel. I'd get the ignition matter fixed first and then I'd start looking for a good carburetor.

Ok, now back to your carburetor question. Here is a cut from a study I did here on Rochester B carburetors a few years ago:

THE POWER SYSTEM


4. And anyone who has ever worked on one of these should know about this. If they ignored it or just didn’t understand what it was, they seriously wasted their time. This scheme was designed to provide additional fuel as needed...meaning whenever the vacuum drops to a certain point. This could be going up a hill, when you are passing another vehicle, when you're using your windshield wipers, operating your wolf whistle, etc. And as we'll learn later, it can also provide additional fuel when you don't need it or want it. Here’s how it works: there is a very important vacuum passage going through your carb which routes manifold vacuum up through the throttle body, on through the main well and up into the air horn. When vacuum is high enough (in my observation it could be around 9” to 11” and in some cases more) that vacuum will pull the power piston up and very slightly off of the spring-loaded power valve (basically a ball pushed up by a weak spring). When vacuum falls below 8 to 11”, then a much stronger spring in the power piston vacuum chamber will force the piston straight down and unseat that ball. When this happens, you get much more fuel in the bowl mast. Oh, I should also tell you the power piston is vented back into the main air horn bore. This is so fuel won’t be sucked past it and back down that vacuum passage I mentioned. Here...you can see what it looks like when the power piston is in the “down” position:

(first image below)

And by contrast it would look like this in the "up" position (away from the power valve):

(third image below)

Rochester used at least 2 styles of power piston designs and I wasn't able to unscramble that egg. One had an open shaft and one had a closed shaft and otherwise they seemed identical.

(second image below)

I have pages of work and several images about the Rochester B (including how to straighten the castings using a 3/8" flat piece of metal and a common gas grill). Just let me know if you want me to resurrect those. They are not a tech tip, by the way. I'm not really completely certain why.