The Stovebolt Site Forums The Shop Area Engine Shop Carb Question

I only drive my truck on weekends. After driving for awhile it will start to idle very rough. If I turn it off and let it cool down, the truck will start right up and run great. Then it’s the same thing all over again.

I don’t smell any gas as if its flooding. I’ve noticed lately some condensation on the base of the carb just above the insulator. It doesn't smell like gas.

My vacuum gauge reads low on the intake manifold. So far I haven’t found any vacuum leaks using carburetor spray. The engine has never been rebuilt. It’s old but usually always starts up without a problem.

I’ve thought about buying a carburetor rebuild kit. The carburetor doesn’t have any identifying numbers to tell me which Rochester B that I have. So buying the correct rebuild kit might be difficult.

http://i7.tinypic.com/21czh8i.jpg

http://i7.tinypic.com/21d04ly.jpg

Are the rebuild kits somewhat universal for the Rochester B?

Is it very difficult to rebuild for a novice?

Do you think the problem could be something other than the carb?

I’m hoping someone can point me in the right direction.

Many thanks.
Mark

I can't speak fpr other brands, but the Standard/Blue Streak brand carb kits usually will cover all varients of a given carb model. They also include a guide of the numbers and where to find it on the carb so you can ID it. I don't think taht the Rochester B is too difficult to overhaul.
You may want to check around the manifold ports for vacuum leaks, and the line to the advance too. Could have a bad gasket.
By the way, what is that peice that is welded to the carb top?

I'll check around for leaks again and loose fittings. A bad gasket might be a good call since it has been moist at the base.

The air filter sits on the ring that is welded on the carb. It was on there when I bought the truck a few years ago. I'm not sure if it was an add-on or if a previous owner bought it that way.

Jim Carter sells a Zenith with the same ridge.
http://www.oldchevytrucks.biz/catalog2/0105.html

Mark

Interesting. It must have been added some where along the way. I know that the original filter doesn't mount that way. Perhaps you have a filter for a different application.

That looks like the standard carb for that era. Any parts place can supply a kit by application. They are really easy to rebuild. Like Longbox posted it could be sucking air around the ports where the manifolds go to the head. Try tightening the bolts. I wonder how someone welded that pot metal like that.

I'll try tightening everything around the manifold and hope for the best. I'm going to go ahead and buy the carb rebuild kit.

Regarding the weld on the carb. I'm not sure if the previous owner did that or purchased the carb that way. It looks weird but it holds the aircleaner on the top well.

Thanks.

Mark,

Your carb looks pretty good from the pics above. Based on the description of your problem, it sounds as if the idle is a little low. I know my truck idles high when I first start it, but after it heats up the idle calms to a dull roar.

Adjust your idle screw a little and give it a try before you get the rebuild kit.

Also check the exhaust manifold heat valve and spring. Make sure the shaft is free and not sticking in the manifold.

To check the spring, unhook it from the anchor pin. Proper adjustment requires only 1/2 turn of the spring, from its unhooked position to slip it over the anchor pin.

Is the exhaust manifold heat valve located just before the point where the exhaust manifold meets the exhaust pipe? I see a valve that is always in the open position.

I checked the tightness of the bolts from the manifold to the head. I re-tightened the carb to the intake manifold and adjusted the idle mixture.

It runs good but I hear a whistling noise that increases with rpm. Its not the fan belt. It sounds as if its coming from the carb. Could that be?

I suffered with similar symptoms...Rochester 1bbls! They do have a tendency to load up when they get warm...one solution...put an adjustable fuel pressure regulator between the fuel pump and the carb,,,dial it down to about 4.5 to 6.0 lbs psi.

Back to the possibility of a vaccuum leak, don't forget the line to the transmission if it is an automatic!

I just bought a 65 with the 292 6 cyl. It had all sorts of gas leak around carb. Based on the time I did not have and the cost (99 + core) of a rebuild 1 barrel, I opted to change the whole thing and glad I did. I put a new insulator on it hooked up choke cable and tightened it down. One air mix screw to adjust and the idle. Very simple took maybe 30 minutes. I have not put a tach on it yet but adjusted it by smoke and just what sounded right. Runs great made a huge differenc.