The Stovebolt Site Forums The Shop Area Engine Shop 1950 GMC Carb ???

Does anyone know the correct part number for my 1950 GMC carb? Are the Chevy and GMC carbs identical? What years use the same part number? THANKS!!!!

the GMC's used a Zenith carb....see oldchevytrucks.com . that is Jim Carter truck parts. 1 800 872 1913. good luck

A 1950 GMC model 100-250 used a Zenith Model 0-11147 Carburetor, GMC Part number 2194114.

The '47-'49 Zeniths were slightly different and there are over 40 individual Zenith applications for '47-'54 GMC trucks. Your profile doesn't say what model truck (1/2, 3/4, or 1 T) you have but since you said pickup, I'm guessing this is the correct one.

I think that you will find just about any Zenith will work, as will many Carters. The GMC trucks will accept a lot of variation.

I think Carter and others do offer a replacement Zenith.

I have a '52 Rochester Model "B" on my '51 GMC, 248 engine. Works great. I don't know where it came from, though; since it was installed by a PO.

Original Zenith (at previously posted) for a 228 CID is Zenith O-11147. Original Zenith for a 248 is O-11148. Both have been superceded by Zenith O-11475, which in turn was superceded by Zenith O-14475. O-14475 is a current part number, and readily available.

Jon.

CarbKing..... Sounds like this dude knows his carbs !!! Do you rebuild carbs King ???

As long as I got your attention King. I have a question on the old 1 barrel Rochester Carbs [ for 216/235's ]. Over time the upper air horns get distorted from over tightening of the screws. Some guys use a double gasket to remidy this. I hear a double gasket mis-alignes the venturies & the carb wont run right. Some guys say the upper air horn must be decked/milled [ or flattened much like a cylinder head ] for it to work after being distorted.
What is your consensus Carb King ??

Mothertrucker - Had Rochester only used 8 screws instead of 4 to hold the airhorn/bowl cover to the bowl on the B series carburetors, this would not be a problem. As they didn't, warpage from heating/cooling cycles causes an internal vacuum leak in the passage controlling the power valve, causing it to stay in the open position (too rich).

Double gaskets MAY work for awhile, but will hasten better repairs.

The procedure we use is very time-consuming, but also very simple and I will post here for do-it-yourselfers.

First obtain some scrap iron plate at least 3/8 inch thick. Drill holes in the plate to align with the airhorn/bowl screws; also machine the plate so that it can be placed flat on either the bowl or the air horn (or use two plates).

Now, screw the airhorn to the plate (snug, but do not tightened. With a feeler guage, measure the clearance between the airhorn and the plate. Take another plate and place on top of the airhorn; and using a rather sophisticated fixture (C-clamp), clamp the two plates together, squeezing the airhorn. Tighten the C-clamp to remove 0.003 inches; NO MORE. Set the assembly in an oven and heat to 400 degrees F. Allow to cool naturally. When cool, the C-Clamp will probably be loose. The heat and tension reverse the warpage process. Repeat until warpage is gone. Repeat for the bowl.

Of course, in another 15 years, the problem will return.

Filing or milling the castings flat obviously removes metal, and the repair will be very temporary, and ruins the castings for proper repair. Best to take the time and do it right the first time.

Oh, one other thing, best to NOT use the oven belonging to your significant other!

Jon.

Carbking, what do you think of those progressive 2bbl Webers? Seems like they would be best of all worlds, with economy and more cfm/power on demand?

Weber carburetors (Italy) are great, if you are looking for a wide range of engine RPM, and have unlimited amounts of money for purchasing tuning parts. Or if a new set-up has been dialed in for ones specific application, buy that rather than trying to re-invent the wheel. If one starts with a "clean sheet of paper", one had best have available a bucket full of jets, air bleeds, venturi, aspirin, etc. for tuning purposes, but the finished product runs well.

Have little experience with the Holley-Weber (USA) progressive two-barrel, but since these came originally on smog-emission engines, believe tuning on a non-original application might be difficult. Do not know availability of tuning parts. Really newer than our area of expertise.

If one is looking at newer carburetors, Carter AFB's are hard to beat, as Carter made them in sizes from 400 to 950 CFM; and offered much in the way of tuning parts (jets, rods, springs), most of which is still fairly available. And obviously, they are progressive. Have run the 400 successfully on many 4 and 6 cylinder engines. Larger sixes (and higher RPM) can use 500 CFM or???

For vintage speed, multiple single carburetors look and can be made to run very well. Generally best to either start with carbs designed to run in multiples (ie Twin-H Hudson) or carbs with mechanical power circuit (ie Carter W-1). Vacuum power circuit carbs can be used, but tuning is less straight-forward.

Jon.

Carb King you are hired !!. Where do I send my cores to be rebuilt at ??

CarbKing;
Another question. What carb do you recommend for a 261? Have a Rochester on mine now and it seems like it's starving for air at higher rpm's and under load IE: going up a hill. Otherwise, it runs the truck just fine. Thanks!

49 geezer, much depends on the physical attributes of the existing unit (bolt spacing, straight or cross flange, manual or automatic choke, etc.) but Carter, Stromberg, and Zenith all offered aftermarket carbs which can probably be adapted. Before throwing rocks at your existing carb, make sure the air cleaner is not partially plugged, or that you don't have ignition problems. Generally, over 90 percent of "carburetor" problems turn out to be ignition.

Jon.

49 Geeze, the original 261 carb was a special Rochester 'B' with a bigger venturi than the 235 rochester for better flow, and used a 59 or 59 main jet. It also had a manual choke. The rochester off a 250 might work with some minor tweeks. I am going to do that with mine although not for long since I am going to be putting on dual 2bbl Holley 94's. I may try one 2bbl '94 before I switch over just for grins but I would have to swap power valves when I go to two so I don't want to build the holleys twice. The 261 seems really choked off with a stock intake, since it has to fill rather big cylinders and I think you will need to go to a better setup for full performance. Don't forget that a 235 Vette motor used the same cam but had three sidedraft carbs and smaller displacement. The Rochester 'B' from the 235 is too small for that engine, and it is even more too small for a 261.

Thanks. Will probably hold out until spring before I paint the engine, dress it up and install a new manifold and possibly twin singles. Probably will go with a nice new valve cover and side plate too. We'll see how much the piggybank has. :mad: